IELTS Academic Reading Practice Test 146

In 1821 Michael Faraday, then a young assistant at the Royal Institution in London, stood a magnet upright in a pool of mercury and suspended a wire above it so that its lower end dipped into the metal. When he connected a battery, the wire began to travel slowly around the magnet and kept moving until the current was switched off. The apparatus was a laboratory demonstration that produced no useful power, but it showed for the first time that electricity could be turned into continuous motion. Every electric motor built since has depended on the same underlying principle.

Faraday was building on an observation made a year earlier by Hans Christian Ørsted, who noticed that a compass needle swung when a wire carrying a current was brought near it. A current, in other words, generates a magnetic field of its own; place a current-carrying wire in a second magnetic field, and the two fields interact to push the wire sideways. This is the force that turns a motor. The physics was only fully described later in the century, but the practical implication was understood almost at once: arrange magnets and wires cleverly, and electricity will do mechanical work.

The first person to build a machine intended to do real work was Thomas Davenport, a blacksmith in Vermont. Having seen an electromagnet at an ironworks, he wound his own coils and by the mid-1830s had constructed a small motor. In 1837 he was granted a patent for an electric motor, and he used his machines to drive a small printing press and to propel a model carriage around a circular track. Davenport hoped to sell his invention to industry, but the motors depended on batteries, and batteries were costly to buy and costly to keep running.

Similar experiments were under way in Europe. The German-born physicist Moritz von Jacobi built an electric motor in 1834 and, with backing from the Russian authorities, fitted one to a paddle boat. In 1839 the vessel carried passengers along the River Neva at a speed of a few kilometres an hour. It was a striking public demonstration, yet the boat was driven by a bank of chemical cells that had to be refilled with acid and zinc, and it was never a serious rival to steam.

The problem was one of energy supply rather than engineering. A battery generates current by consuming metal, and the zinc it used cost far more than the coal burned by a steam engine producing the same amount of power. Motors therefore remained confined to workshops and laboratories, where small size or silence mattered more than running costs, and to a handful of specialist uses. For several decades the electric motor was a solution waiting for a cheap source of electricity.

That source arrived in the late 1860s and 1870s with the self-excited dynamo, developed by several engineers at almost the same moment, among them Werner von Siemens in Germany and Zénobe Gramme in France. A dynamo converts motion into current, and because a motor and a generator are essentially the same machine, the new device had a second use: driven by an engine, it produced current cheaply enough to power motors. Electric drive spread rapidly through industry, and factories that had relied on belts and shafts began to install motors of their own.

Transport was transformed next. In 1888 Frank Sprague opened an electric street railway in Richmond, Virginia, with cars that collected current from an overhead wire, and within a few years electric tramways were running in cities across Europe and North America. Electric lifts made tall buildings practical, and electric motors took over the tasks that had been done by hand or by steam: pumping, hoisting, grinding, sewing and printing. By the end of the century the motor had become an unremarkable part of urban life.

The motors described so far used direct current and needed brushes and a commutator, sliding contacts that wear out and spark. The alternative grew out of the idea of a rotating magnetic field. In 1888 Galileo Ferraris in Italy and Nikola Tesla, working in the United States, independently described motors in which alternating currents in stationary coils created a field that rotated, dragging a simple rotor with it. Tesla's patents were licensed by the Westinghouse company, and the induction motor, which has no sliding contacts at all, became the workhorse of industry. A three-phase version was developed in Germany by Mikhail Dolivo-Dobrovolsky, and in 1891 a three-phase line carried power roughly 175 kilometres from Lauffen to Frankfurt.

Twentieth-century engineers made the motor smaller, cheaper and more efficient, and after the Second World War it moved into the home. Washing machines, refrigerators, fans, power tools and, later, computer drives all depended on it. Traditional designs used electromagnets to provide the magnetic field; modern motors increasingly use permanent magnets based on rare-earth elements, which pack a stronger field into a smaller space.

A large industrial motor can convert well over 90 per cent of the electricity it draws into movement, yet because motors and the equipment they drive are commonly estimated to use around 45 per cent of the world's electricity, even a modest gain in efficiency is worth a great deal. Energy specialists also point out that a badly matched pump or fan can waste more than an efficient motor saves, so attention has shifted from the motor alone to the whole system it drives.

Fifth-generation mobile networks, known almost universally as 5G, are the latest stage in a sequence of radio standards that began with analogue voice calls in the 1980s. Their formal definition was agreed by the International Telecommunication Union, the United Nations agency that coordinates radio spectrum, under a framework called IMT-2020. The targets were ambitious: a peak download rate of 20 gigabits per second, a typical rate for users of 100 megabits per second, a delay of no more than one millisecond in the best conditions, and the ability to connect a million devices within a single square kilometre. The first commercial networks opened in 2019.

Every mobile network carries data on radio waves, and two properties of those waves matter above all. The first is frequency, the number of oscillations per second. Higher frequencies can carry more information, but they fade over shorter distances and pass through walls less easily. The second is bandwidth, the range of frequencies a network is allowed to occupy. A radio channel is like a road: the wider it is, the more traffic can travel along it at once. 5G gains much of its speed simply by occupying wider channels than earlier standards.

Regulators have released two broad ranges of spectrum for 5G. The first, often called sub-6, lies below about seven gigahertz and includes frequencies already used by 4G, which allows a new network to be built alongside an old one. The second lies between roughly 24 and 52 gigahertz, in the region known as millimetre wave because the waves are only millimetres long. Millimetre wave offers vast bandwidth and therefore very high speeds, but its range is measured in hundreds of metres rather than kilometres, and it is blocked by buildings, by foliage and even by heavy rain.

All of these signals are encoded using a technique called orthogonal frequency-division multiplexing, or OFDM. Instead of sending one stream of data on a single carrier wave, the transmitter divides the channel into hundreds or thousands of narrow subcarriers and sends a slice of data on each. The subcarriers are spaced so that they do not interfere with one another. Because each one carries data slowly, the signal survives reflections from buildings and other obstacles that would corrupt a single fast stream. 5G also allows the spacing of subcarriers to be varied, which helps at higher frequencies, where small errors in timing matter more.

Perhaps the most visible change is in the antennas. A 4G base station typically uses a handful of antenna elements; a 5G station may use 64 or more in an array no bigger than a doorstep. This is known as massive multiple-input multiple-output, or massive MIMO. Because the array has many elements, the station can combine their signals so that they add together in one direction and cancel out in others, focusing energy on a single handset rather than spreading it across a cell. The technique, called beamforming, improves both the strength of the signal and the efficiency with which power is used.

Higher frequencies and shorter ranges mean that networks need more base stations. In cities, operators install small cells on lampposts and the sides of buildings to fill gaps in coverage and to add capacity where crowds gather. Delay is attacked in a different way. Part of the network's intelligence is moved closer to the user, so that a request does not have to travel to a distant data centre and back. Engineers also divide a single physical network into separate virtual ones, a practice called network slicing, so that a hospital's equipment and a household's video stream can be given different guarantees on the same infrastructure.

Industry has been quicker than consumers to find uses. Ports, mines and factories have installed private networks to connect cranes, robots and sensors, and fixed wireless access, in which a receiver on a roof replaces a cable, has brought broadband to buildings that no fibre operator would ever reach. For most people, however, the difference between 4G and 5G is felt mainly in crowded places, where the new networks keep working as the old ones slow down.

None of this comes cheaply. Millimetre-wave cells are expensive to build and to connect to the fibre network that carries data back to the core, and many operators have been cautious about deploying them widely. Base stations with large antenna arrays also consume more power than their predecessors, and the sheer number of them raises the total electricity demand of a network even when each is more efficient per bit of data. Measured speeds in everyday use often fall well short of the headline figures, particularly indoors and at the edge of coverage, where the signal is weakest.

Research has therefore turned to ways of getting more from the same spectrum. One approach is to share frequencies dynamically, so that a band allocated to one purpose can be lent to another when it lies idle. Another is to integrate satellite links, which can reach ships, aircraft and remote communities that no terrestrial network will ever cover economically. Laboratories are already experimenting with much higher frequencies, in the terahertz range, for a future generation of standards, though signals there barely penetrate glass. The pattern of mobile communications is unlikely to change: each generation promises more, and delivers it unevenly.

A child in most countries can open a social media account at thirteen. That figure is not the product of any careful scientific judgment. It was written into American law in 1998, when Congress required websites to obtain parental consent before collecting data from children under thirteen, and platforms responded by excluding younger users altogether. The number was never intended as a statement about when adolescence begins, or about when a young person is ready for the pressures of an always-on social world. Nearly three decades later, governments have concluded that the rule is inadequate. Britain's Online Safety Act began to require age checks in 2025, and Australia has barred under-sixteens from holding accounts since the end of that year.

The case for such measures is not frivolous. Surveys consistently find that adolescents spend several hours a day on social platforms, and a substantial minority report that this displaces sleep, exercise and homework. Rates of anxiety and depression among teenagers have risen in many wealthy countries since around 2012, the years in which smartphones became almost universal. The most influential statement of the argument, Jonathan Haidt's book The Anxious Generation, published in 2024, contends that social media has caused a rise in mental illness among young people, particularly girls, and that entry to the platforms should therefore be delayed, much as societies delay driving or drinking.

Other researchers are unconvinced. The psychologist Candice Odgers and others have pointed out that most of the evidence is correlational and that the measured associations between social media use and poor mental health are small — comparable, some have noted, to the association between wellbeing and eating potatoes. A child who is already unhappy may retreat to a phone rather than become unhappy because of one. On this view, a ban addresses a symptom while leaving untouched family circumstances, poverty, exam pressure and the disappearance of places where teenagers can meet without spending money.

Suppose, though, that the case for a minimum age is accepted. The difficulty lies in enforcement, because platforms cannot see who is holding the phone. Age assurance — the industry's preferred term, broader than verification — can take several forms: uploading a passport or driving licence, allowing a bank card to be checked, using a government digital identity wallet, or estimating age from a photograph of the face by analysing its proportions. None of these methods is foolproof, and all of them add friction to the simple act of signing up.

The privacy objection is the most serious. Age checks would be demanded not of the small minority who might be harmed, but of every user of a service, including adults. A system that requires millions of people to prove how old they are before posting a photograph or reading the news creates, in effect, an identity register for the internet, and one that is attractive to criminals and to governments with poor records on surveillance. Technical fixes exist: a third party can confirm an age and issue a token stating only that the holder is over the threshold, so that the platform never learns a date of birth. But such schemes are only as trustworthy as the companies and agencies that run them.

Enforcement, moreover, is porous. Determined children have always been able to use a parent's account, a virtual private network that disguises their location, or a borrowed phone. An age limit drawn at sixteen also treats as identical a mature fifteen-year-old and a vulnerable thirteen-year-old, and it offers nothing to the sixteen-year-old who is already struggling. Nor is exclusion from platforms an unmixed blessing: for a teenager in a small town or a hostile household, an online community may be the only place to find others like themselves.

Weighing these arguments, I find that the balance tilts towards age checks, but only narrowly, and only in a particular form. The state is entitled to set a threshold for a product designed to hold attention and to distribute material that no newspaper would print without checks. But it is not reasonable to place the whole burden of enforcement on children and their parents, nor to require every adult to hand over a passport in order to read a post. A blanket rule that is widely evaded merely teaches young people that rules about technology are for other people.

The more promising approach is to shift obligations onto the companies. Platforms already analyse behaviour in extraordinary detail and can infer with reasonable accuracy which accounts belong to children; they could be required to apply stricter default settings to those users, to switch off features that encourage compulsive use, and to stop recommending content that glamorises self-harm. Age assurance then becomes one tool among several, deployed where the risk is highest, rather than a gate through which everybody must pass.

None of this will satisfy those who want a simple rule, and simple rules have their virtues. But the evidence that social media is the primary cause of adolescent distress remains contested, and legislation built on a contested premise should be proportionate and reversible.

A well-designed system would check age only where necessary, store as little as possible, and be evaluated honestly within a few years. The question worth asking is not whether we can keep the under-sixteens out, but what we owe them once they are in.