Electric charge

From Wikipedia, the free encyclopedia

Electric charge
Electric field of a positive and a negative point charge
Common symbols	Q
SI unit	coulomb
Other units	elementary charge faraday ampere-hour
In SI base units	C = A s
Extensive?	yes
Conserved?	yes
Dimension	T I

Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. There are two types of electric charges; positive and negative (commonly carried by protons and electrons respectively). Like charges repel and unlike attract. An object with an absence of net charge is referred to as neutral. Early knowledge of how charged substances interact is now called classical electrodynamics, and is still accurate for problems that do not require consideration of quantum effects.

Electric charge is a conserved property; the net charge of an isolated system, the amount of positive charge minus the amount of negative charge, cannot change. Electric charge is carried by subatomic particles. In ordinary matter, negative charge is carried by electrons, and positive charge is carried by the protons in the nuclei of atoms. If there are more electrons than protons in a piece of matter, it will have a negative charge, if there are fewer it will have a positive charge, and if there are equal numbers it will be neutral. Charge is quantized; it comes in integer multiples of individual small units called the elementary charge, e, about 1.602×10⁻¹⁹ coulombs, which is the smallest charge which can exist freely (particles called quarks have smaller charges, multiples of 1/3 e, but they are only found in combination, and always combine to form particles with integer charge). The proton has a charge of +e, and the electron has a charge of −e.

An electric charge has an electric field, and if the charge is moving it also generates a magnetic field. The combination of the electric and magnetic field is called the electromagnetic field, and its interaction with charges is the source of the electromagnetic force, which is one of the four fundamental forces in physics. The study of charged particles, and how their interactions are mediated by photons, is called quantum electrodynamics.

The SI derived unit of electric charge is the coulomb (C) named after French physicist Charles-Augustin de Coulomb. In electrical engineering, it is also common to use the ampere-hour (Ah); in physics and chemistry, it is common to use the elementary charge (e as a unit). Chemistry also uses the Faraday constant as the charge on a mole of electrons. The symbol Q often denotes charge.

Overview

Diagram showing field lines and equipotentials around an electron, a negatively charged particle. In an electrically neutral atom, the number of electrons is equal to the number of protons (which are positively charged), resulting in a net zero overall charge

 

Charge is the fundamental property of forms of matter that exhibit electrostatic attraction or repulsion in the presence of other matter. Electric charge is a characteristic property of many subatomic particles. The charges of free-standing particles are integer multiples of the elementary charge e; we say that electric charge is quantized. Michael Faraday, in his electrolysis experiments, was the first to note the discrete nature of electric charge. Robert Millikan's oil drop experiment demonstrated this fact directly, and measured the elementary charge. It has been discovered that one type of particle, quarks, have fractional charges of either −1/3 or +2/3, but it is believed they always occur in multiples of integral charge; free-standing quarks have never been observed. 

By convention, the charge of an electron is negative, −e, while that of a proton is positive, +e. Charged particles whose charges have the same sign repel one another, and particles whose charges have different signs attract. Coulomb's law quantifies the electrostatic force between two particles by asserting that the force is proportional to the product of their charges, and inversely proportional to the square of the distance between them. The charge of an antiparticle equals that of the corresponding particle, but with opposite sign.

The electric charge of a macroscopic object is the sum of the electric charges of the particles that make it up. This charge is often small, because matter is made of atoms, and atoms typically have equal numbers of protons and electrons, in which case their charges cancel out, yielding a net charge of zero, thus making the atom neutral. 

An ion is an atom (or group of atoms) that has lost one or more electrons, giving it a net positive charge (cation), or that has gained one or more electrons, giving it a net negative charge (anion). Monatomic ions are formed from single atoms, while polyatomic ions are formed from two or more atoms that have been bonded together, in each case yielding an ion with a positive or negative net charge. 

Electric field induced by a positive electric charge (top) and a field induced by a negative electric charge (bottom).

 

During formation of macroscopic objects, constituent atoms and ions usually combine to form structures composed of neutral ionic compounds electrically bound to neutral atoms. Thus macroscopic objects tend toward being neutral overall, but macroscopic objects are rarely perfectly net neutral.

Sometimes macroscopic objects contain ions distributed throughout the material, rigidly bound in place, giving an overall net positive or negative charge to the object. Also, macroscopic objects made of conductive elements, can more or less easily (depending on the element) take on or give off electrons, and then maintain a net negative or positive charge indefinitely. When the net electric charge of an object is non-zero and motionless, the phenomenon is known as static electricity. This can easily be produced by rubbing two dissimilar materials together, such as rubbing amber with fur or glass with silk. In this way non-conductive materials can be charged to a significant degree, either positively or negatively. Charge taken from one material is moved to the other material, leaving an opposite charge of the same magnitude behind. The law of conservation of charge always applies, giving the object from which a negative charge is taken a positive charge of the same magnitude, and vice versa. 

Even when an object's net charge is zero, charge can be distributed non-uniformly in the object (e.g., due to an external electromagnetic field, or bound polar molecules). In such cases the object is said to be polarized. The charge due to polarization is known as bound charge, while charge on an object produced by electrons gained or lost from outside the object is called free charge. The motion of electrons in conductive metals in a specific direction is known as electric current.

Units

The SI derived unit of quantity of electric charge is the coulomb (symbol: C). The coulomb is defined as the quantity of charge that passes through the cross section of an electrical conductor carrying one ampere for one second. This unit was proposed in 1946 and ratified in 1948. In modern practice, the phrase "amount of charge" is used instead of "quantity of charge". The amount of charge in 1 electron (elementary charge) is approximately 1.6×10⁻¹⁹ C, and 1 coulomb corresponds to the amount of charge for about 6.24×10¹⁸ electrons. The symbol Q is often used to denote a quantity of electricity or charge. The quantity of electric charge can be directly measured with an electrometer, or indirectly measured with a ballistic galvanometer. 

After finding the quantized character of charge, in 1891 George Stoney proposed the unit 'electron' for this fundamental unit of electrical charge. This was before the discovery of the particle by J. J. Thomson in 1897. The unit is today treated as nameless, referred to as elementary charge, fundamental unit of charge, or simply as e. A measure of charge should be a multiple of the elementary charge e, even if at large scales charge seems to behave as a real quantity. In some contexts it is meaningful to speak of fractions of a charge; for example in the charging of a capacitor, or in the fractional quantum Hall effect. 

The unit faraday is sometimes used in electrochemistry. One faraday of charge is the magnitude of the charge of one mole of electrons, i.e. 96485.33289(59) C. 

In systems of units other than SI such as cgs, electric charge is expressed as combination of only three fundamental quantities (length, mass, and time), and not four, as in SI, where electric charge is a combination of length, mass, time, and electric current.

History

Coulomb's torsion balance

 

From ancient times, persons were familiar with four types of phenomena that today would all be explained using the concept of electric charge: (a) lightning, (b) the torpedo fish (or electric ray), (c) St Elmo's Fire, and (d) that amber rubbed with fur would attract small, light objects. The first account of the amber effect is often attributed to the ancient Greek mathematician Thales of Miletus, who lived from c. 624 – c. 546 BC, but there are doubts about whether Thales left any writings; his account about amber is known from an account from early 200s. This account can be taken as evidence that the phenomenon was known since at least c. 600 BC, but Thales explained this phenomenon as evidence for inanimate objects having a soul. In other words, there was no indication of any conception of electric charge. More generally, the ancient Greeks did not understand the connections among these four kinds of phenomena. The Greeks observed that the charged amber buttons could attract light objects such as hair. They also found that if they rubbed the amber for long enough, they could even get an electric spark to jump, but there is also a claim that no mention of electric sparks appeared until late 17th century. This property derives from the triboelectric effect. In late 1100s, the substance jet, a compacted form of coal, was noted to have an amber effect, and in the middle of the 1500s, Girolamo Fracastoro, discovered that diamond also showed this effect. Some efforts were made by Fracastoro and others, especially Gerolamo Cardano to develop explanations for this phenomenon.

In contrast to astronomy, mechanics, and optics, which had been studied quantitatively since antiquity, the start of ongoing qualitative and quantitative research into electrical phenomena can be marked with the publication of De Magnete by the English scientist William Gilbert in 1600. In this book, there was a small section where Gilbert returned to the amber effect (as he called it) in addressing many of the earlier theories, and coined the New Latin word electrica (from ἤλεκτρον (ēlektron), the Greek word for amber). The Latin word was translated into English as electrics. Gilbert is also credited with the term electrical, while the term electricity came later, first attributed to Sir Thomas Browne in his Pseudodoxia Epidemica from 1646. Gilbert was followed in 1660 by Otto von Guericke, who invented what was probably the first electrostatic generator. Other European pioneers were Robert Boyle, who in 1675 stated that electric attraction and repulsion can act across a vacuum; Stephen Gray, who in 1729 classified materials as conductors and insulators. In 1733 Charles François de Cisternay du Fay, inspired by Gray's work, made a series of experiments (reported in Mémoires de l'Académie Royale des Sciences), showing that more or less all substances could be 'electrified' by rubbing, except for metals and fluids and proposed that electricity comes in two varieties that cancel each other, which he expressed in terms of a two-fluid theory. When glass was rubbed with silk, du Fay said that the glass was charged with vitreous electricity, and, when amber was rubbed with fur, the amber was charged with resinous electricity. Another important two-fluid theory from this time was proposed by Jean-Antoine Nollet (1745). In 1839, Michael Faraday showed that the apparent division between static electricity, current electricity, and bioelectricity was incorrect, and all were a consequence of the behavior of a single kind of electricity appearing in opposite polarities. It is arbitrary which polarity is called positive and which is called negative. Positive charge can be defined as the charge left on a glass rod after being rubbed with silk.

One of the foremost experts on electricity in the 18th century was Benjamin Franklin, who argued in favour of a one-fluid theory of electricity. Franklin imagined electricity as being a type of invisible fluid present in all matter; for example, he believed that it was the glass in a Leyden jar that held the accumulated charge. He posited that rubbing insulating surfaces together caused this fluid to change location, and that a flow of this fluid constitutes an electric current. He also posited that when matter contained too little of the fluid it was negatively charged, and when it had an excess it was positively charged. For a reason that was not recorded, he identified the term positive with vitreous electricity and negative with resinous electricity. William Watson independently arrived at the same explanation at about the same time (1746). 

It is now known that the Franklin–Watson model was fundamentally correct. There is only one kind of electrical charge, and only one variable is required to keep track of the amount of charge. On the other hand, just knowing the charge is not a complete description of the situation. Matter is composed of several kinds of electrically charged particles, and these particles have many properties, not just charge.

The role of charge in electrostatics

All bodies are electrified, but may appear not electrified because of the relatively similar charge of neighboring objects in the environment. An object further electrified + or – creates an equivalent or opposite charge by default in neighboring objects, until those charges can equalize. The effects of attraction can be observed in high-voltage experiments, while lower voltage effects are merely weaker and therefore less obvious. Coulomb's law has a corollary for acceleration in a gravitational field. See also Casimir effect.

The role of charge in static electricity

Static electricity refers to the electric charge of an object and the related electrostatic discharge when two objects are brought together that are not at equilibrium. An electrostatic discharge creates a change in the charge of each of the two objects.

Electrification by friction

When a piece of glass and a piece of resin—neither of which exhibit any electrical properties—are rubbed together and left with the rubbed surfaces in contact, they still exhibit no electrical properties. When separated, they attract each other.

A second piece of glass rubbed with a second piece of resin, then separated and suspended near the former pieces of glass and resin causes these phenomena:

• The two pieces of glass repel each other.
• Each piece of glass attracts each piece of resin.
• The two pieces of resin repel each other.

This attraction and repulsion is an electrical phenomenon, and the bodies that exhibit them are said to be electrified, or electrically charged. Bodies may be electrified in many other ways, as well as by friction. The electrical properties of the two pieces of glass are similar to each other but opposite to those of the two pieces of resin: The glass attracts what the resin repels and repels what the resin attracts. 

If a body electrified in any manner whatsoever behaves as the glass does, that is, if it repels the glass and attracts the resin, the body is said to be vitreously electrified, and if it attracts the glass and repels the resin it is said to be resinously electrified. All electrified bodies are either vitreously or resinously electrified. 

An established convention in the scientific community defines vitreous electrification as positive, and resinous electrification as negative. The exactly opposite properties of the two kinds of electrification justify our indicating them by opposite signs, but the application of the positive sign to one rather than to the other kind must be considered as a matter of arbitrary convention—just as it is a matter of convention in mathematical diagram to reckon positive distances towards the right hand.

No force, either of attraction or of repulsion, can be observed between an electrified body and a body not electrified.

The role of charge in electric current

Electric current is the flow of electric charge through an object, which produces no net loss or gain of electric charge. The most common charge carriers are the positively charged proton and the negatively charged electron. The movement of any of these charged particles constitutes an electric current. In many situations, it suffices to speak of the conventional current without regard to whether it is carried by positive charges moving in the direction of the conventional current or by negative charges moving in the opposite direction. This macroscopic viewpoint is an approximation that simplifies electromagnetic concepts and calculations.

At the opposite extreme, if one looks at the microscopic situation, one sees there are many ways of carrying an electric current, including: a flow of electrons; a flow of electron holes that act like positive particles; and both negative and positive particles (ions or other charged particles) flowing in opposite directions in an electrolytic solution or a plasma.

Beware that, in the common and important case of metallic wires, the direction of the conventional current is opposite to the drift velocity of the actual charge carriers; i.e., the electrons. This is a source of confusion for beginners.

Conservation of electric charge

The total electric charge of an isolated system remains constant regardless of changes within the system itself. This law is inherent to all processes known to physics and can be derived in a local form from gauge invariance of the wave function. The conservation of charge results in the charge-current continuity equation. More generally, the rate of change in charge density ρ within a volume of integration V is equal to the area integral over the current density J through the closed surface S = ∂V, which is in turn equal to the net current I:

${\displaystyle -{\frac {d}{dt}}\int _{V}\rho \,\mathrm {d} V=}$ ${\displaystyle \scriptstyle \partial V}$ ${\displaystyle \mathbf {J} \cdot \mathrm {d} \mathbf {S} =\int J\mathrm {d} S\cos \theta =I.}$

Thus, the conservation of electric charge, as expressed by the continuity equation, gives the result:

${\displaystyle I=-{\frac {\mathrm {d} Q}{\mathrm {d} t}}.}$

The charge transferred between times ${\displaystyle t_{\mathrm {i} }}$ and ${\displaystyle t_{\mathrm {f} }}$ is obtained by integrating both sides:

${\displaystyle Q=\int _{t_{\mathrm {i} }}^{t_{\mathrm {f} }}I\,\mathrm {d} t}$

where I is the net outward current through a closed surface and Q is the electric charge contained within the volume defined by the surface.

Relativistic invariance

Aside from the properties described in articles about electromagnetism, charge is a relativistic invariant. This means that any particle that has charge Q, no matter how fast it goes, always has charge Q. This property has been experimentally verified by showing that the charge of one helium nucleus (two protons and two neutrons bound together in a nucleus and moving around at high speeds) is the same as two deuterium nuclei (one proton and one neutron bound together, but moving much more slowly than they would if they were in a helium nucleus).

Tablet computer

From Wikipedia, the free encyclopedia

Apple's iPad (left) and Amazon's Fire (right), two popular tablet computers.

A tablet computer, commonly shortened to tablet, is a mobile device, typically with a mobile operating system and LCD touchscreen display processing circuitry, and a rechargeable battery in a single thin, flat package. Tablets, being computers, do what other personal computers do, but lack some I/O capabilities that others have. Modern tablets largely resemble modern smartphones, the only differences being that tablets are relatively larger than smartphones, with screens 7 inches (18 cm) or larger, measured diagonally, and may not support access to a cellular network. 

The touchscreen display is operated by gestures executed by finger or stylus instead of the mouse, trackpad, and keyboard of larger computers. Portable computers can be classified according to the presence and appearance of physical keyboards. Two species of tablet, the "slate" and "booklet", do not have physical keyboards and usually accept text and other input by use of a virtual keyboard shown on their touchscreen displays. To compensate for their lack of a physical keyboard, most tablets can connect to independent physical keyboards by wireless Bluetooth or USB; 2-in-1 PCs have keyboards, distinct from tablets. 

The form of the tablet was conceptualized in the middle of the 20th century (Stanley Kubrick depicted fictional tablets in the 1968 science fiction film 2001: A Space Odyssey) and prototyped and developed in the last two decades of that century. In 2010, Apple released the iPad, the first mass-market tablet to achieve widespread popularity. Thereafter tablets rapidly rose in ubiquity and briefly became a large product category used for personal, educational and workplace applications, with sales stabilizing in the mid-2010s.

History

1888 telautograph patent schema

 

Wireless tablet device portrayed in the movie 2001: A Space Odyssey (1968)

The tablet computer and its associated operating system began with the development of pen computing. Electrical devices with data input and output on a flat information display existed as early as 1888 with the telautograph, which used a sheet of paper as display and a pen attached to electromechanical actuators. Throughout the 20th century devices with these characteristics have been imagined and created whether as blueprints, prototypes, or commercial products. In addition to many academic and research systems, several companies released commercial products in the 1980s, with various input/output types tried out:

Fictional and prototype tablets

Tablet computers appeared in a number of works of science fiction in the second half of the 20th century; all helped to promote and disseminate the concept to a wider audience. Examples include:

• Isaac Asimov described a Calculator Pad in his novel Foundation (1951)
• Stanislaw Lem described the Opton in his novel Return from the Stars (1961)
• Numerous similar devices were depicted in Gene Roddenberry's 1966 Star Trek: The Original Series
• Arthur C. Clarke's NewsPad was depicted in Stanley Kubrick's film 2001: A Space Odyssey (1968)
• Douglas Adams described a tablet computer in The Hitchhiker's Guide to the Galaxy and the associated comedy of the same name (1978)
• The sci-fi TV series Star Trek The Next Generation featured tablet computers which were designated as PADDs.
• A device more powerful than today's tablets appeared briefly in The Mote in God's Eye (1974).
• The Star Wars franchise features "datapads", first described in print in 1991's Heir to the Empire and depicted on screen in 1999's The Phantom Menace.

Additionally, real-life projects either proposed or created tablet computers, such as:

• In 1968, computer scientist Alan Kay envisioned a KiddiComp; he developed and described the concept as a Dynabook in his proposal, A personal computer for children of all ages (1972), which outlines functionality similar to that supplied via a laptop computer, or (in some of its other incarnations) a tablet or slate computer, with the exception of near eternal battery life. Adults could also use a Dynabook, but the target audience was children.
• In 1979, the idea of a touchscreen tablet that could detect an external force applied to one point on the screen was patented in Japan by a team at Hitachi consisting of Masao Hotta, Yoshikazu Miyamoto, Norio Yokozawa and Yoshimitsu Oshima, who later received a US patent for their idea.
• In 1992, Atari showed developers the Stylus, later renamed ST-Pad. The ST-Pad was based on the TOS/GEM Atari ST Platform and prototyped early handwriting recognition. Shiraz Shivji's company Momentus demonstrated in the same time a failed x86 MS-DOS based Pen Computer with its own GUI.
• In 1994, the European Union initiated the NewsPad project, inspired by Clarke and Kubrick's fictional work. Acorn Computers developed and delivered an ARM-based touch screen tablet computer for this program, branding it the "NewsPad"; the project ended in 1997.
• During the November 2000 COMDEX, Microsoft used the term Tablet PC to describe a prototype handheld device they were demonstrating.
• In 2001, Ericsson Mobile Communications announced an experimental product named the DelphiPad, which was developed in cooperation with the Centre for Wireless Communications in Singapore, with a touch-sensitive screen, Netscape Navigator as a web browser, and Linux as its operating system.

Early tablets

Apple Newton MessagePad, Apple's first produced tablet, released in 1993.

 

Following earlier tablet computer products such as the Pencept PenPad, and the CIC Handwriter, in September 1989, GRiD Systems released the first commercially successful tablet computer, the GRiDPad. All three products were based on extended versions of the MS-DOS operating system. In 1992, IBM announced (in April) and shipped to developers (in October) the 2521 ThinkPad, which ran the GO Corporation's PenPoint OS. Also based on PenPoint was AT&T's EO Personal Communicator from 1993, which ran on AT&T's own hardware, including their own AT&T Hobbit CPU. Apple Computer launched the Apple Newton personal digital assistant in 1993. It used Apple's own new Newton OS, initially running on hardware manufactured by Motorola and incorporating an ARM CPU, that Apple had specifically co-developed with Acorn Computers. The operating system and platform design were later licensed to Sharp and Digital Ocean, who went on to manufacture their own variants. 

In 1996, Palm, Inc. released the first of the Palm OS based PalmPilot touch and stylus based PDA, the touch based devices initially incorporating a Motorola Dragonball (68000) CPU. Also in 1996 Fujitsu released the Stylistic 1000 tablet format PC, running Microsoft Windows 95, on a 100 MHz AMD486 DX4 CPU, with 8 MB RAM offering stylus input, with the option of connecting a conventional Keyboard and mouse. Intel announced a StrongARM processor-based touchscreen tablet computer in 1999, under the name WebPAD. It was later re-branded as the "Intel Web Tablet". In 2000, Norwegian company Screen Media AS and the German company Dosch & Amand Gmbh released the " FreePad". It was based on Linux and used the Opera browser. Internet access was provided by DECT DMAP, only available in Europe and provided up to 10Mbit/s. The device had 16 MB storage, 32 MB of RAM and x86 compatible 166 MHz "Geode"-Microcontroller by National Semiconductor. The screen was 10.4" or 12.1" and was touch sensitive. It had slots for SIM cards to enable support of television set-up box. FreePad were sold in Norway and the Middle East; but the company was dissolved in 2003. 

A Fujitsu Siemens Lifebook tablet running Windows XP, released in 2003

 

In April 2000, Microsoft launched the Pocket PC 2000, using their touch capable Windows CE 3.0 operating system. The devices were manufactured by several manufacturers, based on a mix of: x86, MIPS, ARM, and SuperH hardware. In 2002, Microsoft attempted to define the Microsoft Tablet PC as a mobile computer for field work in business, though their devices failed, mainly due to pricing and usability decisions that limited them to their original purpose - such as the existing devices being too heavy to be held with one hand for extended periods, and having legacy applications created for desktop interfaces and not well adapted to the slate format.

The Nokia N800

 

Nokia had plans for an Internet tablet since before 2000. An early model was test manufactured in 2001, the Nokia M510, which was running on EPOC and featuring an Opera browser, speakers and a 10-inch 800×600 screen, but it was not released because of fears that the market was not ready for it. Nokia entered the tablet space in May 2005 with the Nokia 770 running Maemo, a Debian-based Linux distribution custom-made for their Internet tablet line. The user interface and application framework layer, named Hildon, was an early instance of a software platform for generic computing in a tablet device intended for internet consumption. But Nokia didn't commit to it as their only platform for their future mobile devices and the project competed against other in-house platforms and later replaced it with the Series 60. Nokia used the term internet tablet to refer to a portable information appliance that focused on Internet use and media consumption, in the range between a personal digital assistant (PDA) and an Ultra-Mobile PC (UMPC). They made two mobile phones, the N900 that runs Maemo, and N9 that run Meego.

Before the release of iPad, Axiotron introduced an aftermarket, heavily modified Apple MacBook called Modbook, a Mac OS X-based tablet computer. The Modbook uses Apple's Inkwell for handwriting and gesture recognition, and uses digitization hardware from Wacom. To get Mac OS X to talk to the digitizer on the integrated tablet, the Modbook was supplied with a third-party driver.

Following the launch of the Ultra-mobile PC, Intel started the Mobile Internet Device initiative, which took the same hardware and combined it with a tabletized Linux configuration. Intel co-developed the lightweight Moblin (mobile Linux) operating system following the successful launch of the Atom CPU series on netbooks. In 2010, Nokia and Intel combined the Maemo and Moblin projects to form MeeGo, a Linux-based operating system supports netbooks and tablets. The first tablet using MeeGo was the Neofonie WeTab launched September 2010 in Germany. The WeTab used an extended version of the MeeGo operating system called WeTab OS. WeTab OS adds runtimes for Android and Adobe AIR and provides a proprietary user interface optimized for the WeTab device. On September 27, 2011 the Linux Foundation announced that MeeGo would be replaced in 2012 by Tizen.

Modern tablets

Apple's iPad and iPad Pro

 

Android was the first of the 2000s-era dominating platforms for tablet computers to reach the market. In 2008, the first plans for Android-based tablets appeared. The first products were released in 2009. Among them was the Archos 5, a pocket-sized model with a 5-inch touchscreen, that was first released with a proprietary operating system and later (in 2009) released with Android 1.4. The Camangi WebStation was released in Q2 2009. The first LTE Android tablet appeared late 2009 and was made by ICD for Verizon. This unit was called the Ultra, but a version called Vega was released around the same time. Ultra had a 7-inch display while Vega's was 15 inches. Many more products followed in 2010. Several manufacturers waited for Android Honeycomb, specifically adapted for use with tablets, which debuted in February 2011.

Apple is often credited for defining a new class of consumer device with the iPad, which shaped the commercial market for tablets in the following years, and was the most successful tablet at the time of its release. iPads and competing devices were tested by the US military in 2011 and cleared for secure use in 2013. Its debut in 2010 pushed tablets into the mainstream. Samsung's Galaxy Tab and others followed, continuing the trends towards the features listed above. In March 2012, PC Magazine reported that 31% of U.S. Internet users owned a tablet, used mainly for viewing published content such as video and news. The top-selling line of devices was Apple's iPad with 100 million sold between its release in April 2010 and mid-October 2012, but iPad market share (number of units) dropped to 36% in 2013 with Android tablets climbing to 62%. Android tablet sales volume was 121 million devices, plus 52 million, between 2012 and 2013 respectively. Individual brands of Android operating system devices or compatibles follow iPad with Amazon's Kindle Fire with 7 million, and Barnes & Noble's Nook with 5 million.

The BlackBerry PlayBook was announced in September 2010 that ran the BlackBerry Tablet OS. The BlackBerry PlayBook was officially released to US and Canadian consumers on April 19, 2011. Hewlett Packard announced that the TouchPad, running WebOS 3.0 on a 1.2 GHz Qualcomm Snapdragon CPU, would be released in June 2011. On August 18, 2011, HP announced the discontinuation of the TouchPad, due to sluggish sales. In 2013, the Mozilla Foundation announced a prototype tablet model with Foxconn which ran on Firefox OS. Firefox OS was discontinued in 2016. The Canonical hinted that Ubuntu would be available on tablets by 2014. In February 2016 there was a commercial release of the BQ Aquaris Ubuntu tablet utilizing the Ubuntu Touch operating system. Canonical terminated support for the project due to lack of market interest on 5 April 2017 and it was then adopted by the UBports as a community project.

As of February 2014, 83% of mobile app developers were targeting tablets, but 93% of developers were targeting smartphones. By 2014 around 23% of B2B companies were said to have deployed tablets for sales-related activities, according to a survey report by Corporate Visions. The iPad holds majority use in North America, Western Europe, Japan, Australia, and most of the Americas. Android tablets are more popular in most of Asia (China and Russia an exception), Africa and Eastern Europe. In 2015 tablet sales did not increase. Apple remained the largest seller but its market share declined below 25%. Samsung vice president Gary Riding said early in 2016 that tablets were only doing well among those using them for work. Newer models were more expensive and designed for a keyboard and stylus, which reflected the changing uses. As of early 2016, Android reigns over the market with 65%. Apple takes the number 2 spot with 26%, and Windows take a distant third with the remaining 9%. In 2018, out of 4.4 billion computing devices Android accounted for 2 billion, iOS for 1 billion, and the remainder were PCs, in various forms (desktop, notebook, or tablet), running various operating systems (Windows, macOS, ChromeOS, Linux, etc.).

In late 2017, the iPad Pro received the iOS 11 update, adding the ability to run multiple windows, drag and drop from one app to another, and browse a user's files.

Types

Crossover tablet device types from 2014: Microsoft Surface Pro 3 laplet and Sony Xperia Z Ultra phablet, next to a generic blue lighter to indicate their sizes.

 

Comparison of several mini tablet computers: Amazon Kindle Fire (left), iPad Mini (center), and Google Nexus 7 (right)

 

Samsung's Galaxy Note series were the first commercially successful phablets

 

Microsoft Surface Pro 3, a prominent 2-in-1 detachable tablet

 

Lenovo Yoga, a 2-in-1 convertible tablet, with a physical keyboard that can be folded at any angle

 

Asus Transformer Pad, a 2-in-1 detachable tablet, powered by the Android operating system

 

Nvidia Shield Tablet, notable gaming tablet

 

Tablets can be loosely grouped into several categories by physical size, kind of operating system installed, input and output technology, and uses.

Slate

The size of a slate varies, but slates begin at 6 inches (approximately 15 cm). Some models in the larger than 10-inch (25 cm) category include the Samsung Galaxy Tab Pro 12.2 at 12.2 inches (31 cm), the Toshiba Excite at 13.3 inches (33 cm) and the Dell XPS 18 at 18.4 inches (47 cm). As of March 2013, the thinnest tablet on the market was the Sony Xperia Tablet Z at only 0.27 inches (6.9 mm) thick. On September 9, 2015, Apple released the iPad Pro with a 12.9 inches (33 cm) screen size, larger than the regular iPad.

Mini tablet

Mini tablets are smaller and weigh less than slates, with typical screen sizes between 7–8 inches (18–20 cm). The first commercially successful mini tablets were introduced by Amazon.com (Kindle Fire), Barnes & Noble (Nook Tablet), and Samsung (Galaxy Tab) in 2011; and by Google (Nexus 7) in 2012. They operate identically to ordinary tablets but have lower specifications compared to them.

On September 14, 2012, Amazon, Inc. released an upgraded version of the Kindle Fire, the Kindle Fire HD, with higher screen resolution and more features compared to its predecessor, yet remaining only 7 inches. In October 2012, Apple released the iPad Mini with a 7.9 inch screen size, about 2 inches smaller than the regular iPad, but less powerful than the then current iPad 3. On July 24, 2013, Google released an upgraded version of the Nexus 7, with FHD display, dual cameras, stereo speakers, more color accuracy, performance improvement, built-in wireless charging, and a variant with 4G LTE support for AT&T, T-Mobile, and Verizon. In September 2013, Amazon further updated the Fire tablet with the Kindle Fire HDX. In November 2013, Apple released the iPad Mini 2, which remained at 7.9 inches and nearly matched the hardware of the iPad Air.

Phablet

Smartphones and tablets are similar devices, differentiated by the former typically having smaller screens and most tablets lacking cellular network capability. Since 2010, crossover touchscreen smartphones with screens larger than 5 inches have been released. That size is generally considered larger than a traditional smartphone, creating the hybrid category of the phablet by Forbes and other publications. "Phablet" is a portmanteau of "phone" and "tablet".

At the time of the introduction of the first phablets, they had screens of 5.3 to 5.5 inches, but as of 2017 screen sizes up to 5.5 inches are considered typical. Examples of phablets from 2017 and onward are the Samsung Galaxy Note series (newer models of 5.7 inches), the LG V10/V20 (5.7 inches), the Sony Xperia XA Ultra [6 inches], the Huawei Mate 9 (5.9 inches), and the Huawei Honor (MediaPad) X2 (7 inches).

2-in-1

Distinct from tablets, 2-in-1 PCs all have physical keyboards, but they are either concealable by folding them back and under the touchscreen ("2-in-1 convertible") or detachable ("2-in-1 detachable"), but 2-in-1s typically also can display a virtual keyboard on their touchscreens when their physical keyboards are concealed or detached. Some 2-in-1s have processors and operating systems like those of laptops, while having the flexibility of operation as a tablet. A 2-in-1 PC is a hybrid or combination of a tablet and laptop computer that has features of both. An essential feature of a 2-in-1 is a desktop operating system, such as Windows 10, as opposed to a mobile operating system. Additionally, 2-in-1s may have typical laptop I/O ports, such as USB 3 and DisplayPort, and may connect to traditional PC peripheral devices and external displays. Therefore, they are distinct from tablets, although they can operate just like them. Simple tablets are primarily used as media consumption devices, while 2-in-1s have capacity for both media consumption and content creation, and therefore 2-in-1s are often called "laptop" or "desktop replacement computers".

There are two species of 2-in-1s:

• Convertibles have a chassis design by which their physical keyboard may be concealed by flipping/folding the keyboard behind the chassis. Examples include 2-in-1 PCs of the Lenovo Yoga series.
• Detachables or Hybrids have physical keyboards that may be detached from their chassis, even while the 2-in-1 is operating. Examples include 2-in-1 PCs of the Asus Transformer Pad series, the iPad Pro, and the Microsoft Surface Book and Surface Pro.

Gaming tablet

Some tablets are modified by adding physical gamepad buttons such as D-pad and thumb sticks for better gaming experience combined with the touchscreen and all other features of a typical tablet computer. Most of these tablets are targeted to run native OS games and emulator games. Nvidia's Shield Tablet, with an 8-inch (200 mm) display, and running Android, is an example. It runs Android games purchased from Google Play store. PC games can also be streamed to the tablet from computers with some higher end models of Nvidia-powered video cards. The Nintendo Switch hybrid console is also a gaming tablet that runs on Nintendo Switch system software, features detachable Joy-Con controllers with motion controls and three gaming modes: table-top mode using its kickstand, traditional docked/TV mode and handheld mode.

Booklet

Booklets are dual-touchscreen tablet computers with a clamshell design that can fold like a laptop. Examples include the Microsoft Courier, which was discontinued in 2010, the Sony Tablet P (which was considered a flop), and the Toshiba Libretto W100.

Customized business tablet

Customized business tablets are built specifically for a business customer's particular needs from a hardware and software perspective, and delivered in a business-to-business transaction. For example, in hardware, a transportation company may find that the consumer-grade GPS module in an off-the-shelf tablet provides insufficient accuracy, so a tablet can be customized and embedded with a professional-grade antenna to provide a better GPS signal. Such tablets may also be ruggedized for field use. For a software example, the same transportation company might remove certain software functions in the Android system, such as the internet browser, to reduce costs from unnecessary cellular network data consumption of an employee, and add custom package management software. Other applications may call for a resistive touchscreen and other special hardware and software.

Games on a Ziosk table ordering tablet at an Olive Garden restaurant

 

A table ordering tablet is a touchscreen tablet computer designed for use in casual restaurants. Such devices allow users to order food and drinks, play games and pay their bill. Since 2013, restaurant chains including Chili's, Olive Garden, and Red Robin have adopted them. As of 2014, the two most popular brands were Ziosk and Presto. The devices have been criticized by servers who claim that some restaurants determine their hours based on customer feedback in areas unrelated to service.

Hardware

System architecture

Two major architectures dominate the tablet market, ARM Holdings' ARM architecture and Intel's and AMD's x86. Intel's x86, including x86-64 has powered the "IBM compatible" PC since 1981 and Apple's Macintosh computers since 2006. The CPUs have been incorporated into tablet PCs over the years and generally offer greater performance along with the ability to run full versions of Microsoft Windows, along with Windows desktop and enterprise applications. Non-Windows based x86 tablets include the JooJoo. Intel announced plans to enter the tablet market with its Atom in 2010. In October 2013, Intel's foundry operation announced plans to build FPGA-based quad cores for ARM and x86 processors.

ARM has been the CPU architecture of choice for manufacturers of smartphones (95% ARM), PDAs, digital cameras (80% ARM), set-top boxes, DSL routers, smart televisions (70% ARM), storage devices and tablet computers (95% ARM). This dominance began with the release of the mobile-focused and comparatively power-efficient 32-bit ARM610 processor originally designed for the Apple Newton in 1993 and ARM3-using Acorn A4 laptop in 1992. The chip was adopted by Psion, Palm and Nokia for PDAs and later smartphones, camera phones, cameras, etc. ARM's licensing model supported this success by allowing device manufacturers to license, alter and fabricate custom SoC derivatives tailored to their own products. This has helped manufacturers extend battery life and shrink component count along with the size of devices.

The multiple licensees ensured that multiple fabricators could supply near-identical products, while encouraging price competition. This forced unit prices down to a fraction of their x86 equivalents. The architecture has historically had limited support from Microsoft, with only Windows CE available, but with the 2012 release of Windows 8, Microsoft announced additional support for the architecture, shipping their own ARM-based tablet computer, branded the Microsoft Surface, as well as an x86-64 Intel Core i5 variant branded as Microsoft Surface Pro. Intel tablet chip sales were 1 million units in 2012, and 12 million units in 2013. Intel chairman Andy Bryant has stated that its 2014 goal is to quadruple its tablet chip sales to 40 million units by the end of that year, as an investment for 2015.

Display

Samsung Galaxy Tab demonstrating multi-touch

 

A key component among tablet computers is touch input on a touchscreen liquid-crystal display (LCD). This allows the user to navigate easily and type with a virtual keyboard on the screen or press other icons on the screen to open apps or files. The first tablet to do this was the GRiDPad by GRiD Systems Corporation; the tablet featured both a stylus, a pen-like tool to aid with precision in a touchscreen device as well as an on-screen keyboard. The system must respond to on-screen touches rather than clicks of a keyboard or mouse. This operation makes precise use of our eye–hand coordination.

Touchscreens usually come in one of two forms:

1. Resistive touchscreens are passive and respond to pressure on the screen. They allow a high level of precision, useful in emulating a pointer (as is common in tablet computers) but may require calibration. Because of the high resolution, a stylus or fingernail is often used. Stylus-oriented systems are less suited to multi-touch.
2. Capacitive touchscreens tend to be less accurate, but more responsive than resistive devices. Because they require a conductive material, such as a finger tip, for input, they are not common among stylus-oriented devices, but are prominent on consumer devices. Most finger-driven capacitive screens do not currently support pressure input (except for the iPhone 6S and later models), but some tablets use a pressure-sensitive stylus or active pen.
3. Some tablets can recognize individual palms, while some professional-grade tablets use pressure-sensitive films, such as those on graphics tablets. Some capacitive touch-screens can detect the size of the touched area and the pressure used.

Since mid-2010s, most tablets use capacitive touchscreens with multi-touch, unlike earlier resistive touchscreen devices which users needed styluses in order to perform inputs.

Handwriting recognition

Chinese characters like this one meaning "person" can be written by handwriting recognition (, Mandarin: rén, Korean: in, Japanese: jin, nin; hito, Cantonese: jan4). The character has two strokes, the first shown here in brown, and the second in red. The black area represents the starting position of the writing instrument.

 

Some ARM powered tablets, such as the Galaxy Note 10, support a stylus and support handwriting recognition. Wacom and N-trig digital pens provide approximately 2500 DPI resolution for handwriting, exceeding the resolution of capacitive touch screens by more than a factor of 10. These pens also support pressure sensitivity, allowing for "variable-width stroke-based" characters, such as Chinese/Japanese/Korean writing, due to their built-in capability of "pressure sensing". Pressure is also used in digital art applications such as Autodesk Sketchbook. Apps exist on both iOS and Android platforms for handwriting recognition and in 2015 Google introduced its own handwriting input with support for 82 languages.

Other features

After 2007, with access to capacitive screens and the success of the iPhone, other features became common, such as multi-touch features (in which the user can touch the screen in multiple places to trigger actions and other natural user interface features, as well as flash memory solid state storage and "instant on" warm-booting; external USB and Bluetooth keyboards defined tablets.

Most tablets released since mid-2010 use a version of an ARM processor for longer battery life. The ARM Cortex family is powerful enough for tasks such as internet browsing, light production work and mobile games.

Other features are: High-definition, anti-glare display, touchscreen, lower weight and longer battery life than a comparably-sized laptop, wireless local area and internet connectivity (usually with Wi-Fi standard and optional mobile broadband), Bluetooth for connecting peripherals and communicating with local devices, ports for wired connections and charging, for example USB ports, Early devices had IR support and could work as a TV remote controller, docking station, keyboard and additional connectivity, on-board flash memory, ports for removable storage, various cloud storage services for backup and syncing data across devices, Local storage on a LAN

• Speech recognition Google introduced voice input in Android 2.1 in 2009 and voice actions in 2.2 in 2010, with up to five languages (now around 40). Siri was introduced as a system-wide personal assistant on the iPhone 4S in 2011 and now supports nearly 20 languages. In both cases the voice input is sent to central servers to perform general speech recognition and therefore requires a network connection for more than simple commands.
• Near field communication with other compatible devices including ISO/IEC 14443 RFID tags.

Software

Operating system

Tablets, like conventional PCs, use several different operating systems, though dual-booting is rare. Tablet operating systems come in two classes:

• Desktop computer operating system
• Mobile operating system

Desktop OS-based tablets are currently thicker and heavier. They require more storage and more cooling and give less battery life. They can run processor-intensive graphical applications in addition to mobile apps, and have more ports.

Mobile-based tablets are the reverse, and run only mobile apps. They can use battery life conservatively because the processor is significantly smaller. This allows the battery to last much longer than the common laptop.

In Q1 2018, Android tablets had 62% of the market, Apple's iOS had 23.4% of the market and Windows 10 had 14.6% of the market.

Android

Android is a Linux-based operating system that Google offers as open source under the Apache license. It is designed primarily for mobile devices such as smartphones and tablet computers. Android supports low-cost ARM systems and others. The first tablets running Android were released in 2009. Vendors such as Motorola and Lenovo delayed deployment of their tablets until after 2011, when Android was reworked to include more tablet features. Android 3.0 (Honeycomb), released in 2011 and later versions support larger screen sizes, mainly tablets, and have access to the Google Play service. Android includes operating system, middleware and key applications. Other vendors sell customized Android tablets, such as Kindle Fire and Nook, which are used to consume mobile content and provide their own app store, rather than using the larger Google Play system, thereby fragmenting the Android market.

Chrome OS

Several devices that run Chrome OS came on the market in 2017-2019, as tablets, or as 2-in-1s with touchscreen and 360-degree hinge.

iOS

The iPad runs on iOS, which was created for the iPhone and iPod Touch. The first iPad was released in 2011. Although built on the same underlying Unix implementation as MacOS, its user interface is radically different. iOS is designed for fingers and has none of the features that required a stylus on earlier tablets. Apple introduced multi-touch gestures, such as moving two fingers apart or together to zoom in or out, also known as "pinch to zoom". iOS is built for the ARM architecture.

Windows

Following Windows for Pen Computing for Windows 3.1 in 1991, Microsoft supported tablets running Windows XP under the Microsoft Tablet PC name. Microsoft Tablet PCs were pen-based, fully functional x86 PCs with handwriting and voice recognition functionality. Windows XP Tablet PC Edition provided pen support. Tablet support was added to both Home and Business versions of Windows Vista and Windows 7. Tablets running Windows could use the touchscreen for mouse input, hand writing recognition and gesture support. Following Tablet PC, Microsoft announced the Ultra-mobile PC initiative in 2006 which brought Windows tablets to a smaller, touch-centric form factor. In 2008, Microsoft showed a prototype of a two-screen tablet called Microsoft Courier, but cancelled the project. 

In 2012, Microsoft released Windows 8, which features significant changes to various aspects of the operating system's user interface and platform which are designed for touch-based devices such as tablets. The operating system also introduced an application store and a new style of application optimized primarily for use on tablets. Microsoft also introduced Windows RT, an edition of Windows 8 for use on ARM-based devices. The launch of Windows 8 and RT was accompanied by the release of devices with the two operating systems by various manufacturers (including Microsoft themselves, with the release of Surface), such as slate tablets, hybrids, and convertibles.

Released in July 2015, Windows 10 introduces what Microsoft described as "universal apps"; expanding on Metro-style apps, these apps can be designed to run across multiple Microsoft product families with nearly identical code‍—‌including PCs, tablets, smartphones, embedded systems, Xbox One, Surface Hub and Windows Holographic. The Windows user interface was revised to handle transitions between a mouse-oriented interface and a touchscreen-optimized interface based on available input devices‍—‌particularly on 2-in-1 PCs; both interfaces include an updated Start menu. Windows 10 replaced all earlier editions of Windows.

Hybrid OS operation

Several hardware companies have built hybrid devices with the possibility to work with both the Windows 10 and Android operating systems.

Application store

Apps that do not come pre-installed with the system are supplied through online distribution. These sources, known as "app stores", provide centralized catalogs of software and allow "one click" on-device software purchasing, installation and updates.

Mobile device suppliers may adopt a "walled garden" approach, wherein the supplier controls what software applications ("apps") are available. Software development kits are restricted to approved software developers. This can be used to reduce the impact of malware, provide software with an approved content rating, control application quality and exclude competing vendors. Apple, Google, Amazon, Microsoft and Barnes & Noble all adopted the strategy. B&N originally allowed arbitrary apps to be installed, but, in December 2011, excluded third parties. Apple and IBM have agreed to cooperate in cross-selling IBM-developed applications for iPads and iPhones in enterprise-level accounts. Proponents of open source software say that it violates the spirit of personal control that traditional personal computers have always provided.

Sales

Around 2010, tablet use by businesses jumped, as business have started to use them for conferences, events, and trade shows. In 2012, Intel reported that their tablet program improved productivity for about 19,000 of their employees by an average of 57 minutes a day. In October 2012, display screen shipments for tablets began surpassing shipments for laptop display screens. Tablets are increasingly used in the construction industry to look at blueprints, field documentation and other relevant information on the device instead of carrying around large amounts of paper.

As of the beginning of 2014, 44% of US online consumers own tablets, a significant jump from 5% in 2011. Tablet use has also become increasingly common among children. A 2014 survey found that mobiles were the most frequently used object for play among American children under the age of 12. Mobiles were used more often in play than video game consoles, board games, puzzles, play vehicles, blocks and dolls/action figures. Despite this, the majority of parents said that a mobile was "never" or only "sometimes" a toy. As of 2014, nearly two-thirds of American 2- to 10-year-olds have access to a tablet or e-reader. The large use of tablets by adults is as a personal internet-connected TV. A 2015 study found that a third of children under five have their own tablet device. By 2017, tablet sales worldwide had surpassed sales of desktop computers, and worldwide PC sales were flat for the first quarter of 2018.

By manufacturer

Tablet market share (in percent)

Vendor	Q3 2012	Q3 2013	Q3 2014	Q3 2015	Q3 2016	Q3 2017	Q3 2018
Apple	40.2	29.7	22.1	19.6	21.5	25.9	26.6
Samsung	12.4	22.2	17.4	16.0	15.1	15.0	14.6
Others	47.3	49.1	60.9	64.4	63.4	59.2	58.8

By operating system

According to a survey conducted by the Online Publishers Association (OPA) now called Digital Content Next (DCN) in March 2012, it found that 72% of tablet owners had an iPad, while 32% had an Android tablet. By 2012, Android tablet adoption had increased. 52% of tablet owners owned an iPad, while 51% owned an Android-powered tablet (percentages do not add up to 100% because some tablet owners own more than one type). By end of 2013, Android's market share rose to 61.9%, followed by iOS at 36%. By late 2014, Android's market share rose to 72%, followed by iOS at 22.3% and Windows at 5.7%. As of early 2016, Android has 65% marketshare, Apple has 26% and Windows has 9% marketshare. In Q1 2018, Android tablets had 62% of the market, Apple's iOS had 23.4% of the market and Windows 10 had 14.6% of the market.

Use

Sleep

The blue wavelength of light from back-lit tablets may impact one's ability to fall asleep when reading at night, through the suppression of melatonin. Experts at Harvard Medical School suggest limiting tablets for reading use in the evening. Those who have a delayed body clock, such as teenagers, which makes them prone to stay up late in the evening and sleep later in the morning, may be at particular risk for increases in sleep deficiencies. A PC app such as F.lux and Android apps such as CF.lumen and Twilight attempt to decrease the impact on sleep by filtering blue wavelengths from the display. iOS 9.3 includes Night Shift that shifts the colors of the device's display to be warmer during the later hours.

By plane

Because of, among other things, electromagnetic waves emitted by this type of device, the use of any type of electronic device during the take-off and landing phases was totally prohibited on board commercial flights. On 13 November 2013, the European Aviation Safety Agency (EASA) announced that the use of mobile terminals could be authorized on the flights of European airlines during these phases from 2014 onward, on the condition that the cellular functions are deactivated ("airplane" mode activated). EASA then formally confirmed this information on December 11, 2013. Tablets, e-readers, smartphones, MP3 players, and portable gaming consoles are affected by these announcements.

Tourism

Some French historical monuments are equipped with digital tactile tablets called "HistoPad". It is an application integrated with an iPad mini offering an interaction in augmented and virtual reality with several pieces of the visit, the visitor being able to take control of his visit in an interactive and personalized way.

Professional use for specific sectors

Some professionals - for example, in the construction industry, insurance experts, lifeguards or surveyors - use so-called rugged shelf models in the field that can withstand extreme hot or cold shocks or climatic environments. even hardened. In addition, via satellite Iridium type of connectivity, this type of tablet, such as Thorium X for example, can be used in areas where there is no connectivity. United States Army helicopter pilots are moving to tablets as electronic flight bags, where the advantages are “Money saving, synchronization [of large groups of users], and relevance [of information]” — Chief Warrant Officer 5 Steve Donahue.