IELTS Academic Reading Practice Test 199

For most of the nineteenth century the guitar was a quiet instrument. In an orchestra it was easily drowned, and in the dance bands that grew popular in the 1920s it stood no chance against drums, pianos and brass. Players needed volume, and the instrument they reached for was not the guitar but the banjo, whose drum-like body cut through the noise of a crowded hall. The banjo, however, had a harsh tone that many musicians disliked. What was wanted was a guitar that could be as loud as a trumpet without losing its character.

The solution came from electrical engineering rather than woodwork. In the 1920s inventors began applying to instruments the idea behind the microphone, which converts sound into an electrical signal. The crucial component was the magnetic pickup: a coil of fine wire wound around a magnet and placed close to the strings. Because the strings are made of steel, they disturb the magnetic field above the magnet, and the vibration induces a small alternating current in the coil, which can then be amplified. The principle at work, electromagnetic induction, had been described by Michael Faraday in 1831.

One of the first to attempt this commercially was an engineer named Lloyd Loar, who worked for the Gibson company and is known to have experimented with amplifying string instruments in the early 1920s. Gibson, however, was not persuaded, and Loar left the firm in 1924; the company did not develop his ideas.

The first commercially produced electric guitar appeared in the early 1930s. George Beauchamp, a musician and inventor, and Adolph Rickenbacker, an engineer, founded a company in Los Angeles whose small lap steel guitar had a body cast from aluminium. Its pickup wrapped around the strings like a horseshoe and gave a strong signal, and the round shape earned the instrument the nickname of the frying pan. A patent covering the pickup was granted in 1937. The guitar was designed to lie flat on the player's lap, with a metal bar rather than fingers stopping the strings.

The idea soon reached the mainstream. In 1936 Gibson introduced the ES-150, the letters standing for electric Spanish: a conventional-looking instrument with a pickup built into its body. Early sales were modest, but in 1939 the jazz guitarist Charlie Christian began playing one with Benny Goodman's band, and his long, flowing single-note lines showed what the amplified guitar could do. The ES-150 had a hollow body, however, and at the volumes demanded by dance halls the amplified sound fed back into the pickup, producing the howl known as feedback.

The obvious answer was to abandon the hollow body altogether. A solid block of wood cannot resonate as a soundbox does, so it resists feedback. Several players and makers built solid instruments in the 1940s, and the most influential was the guitarist Les Paul, who assembled what became known as the Log from a length of pine with the two wings of a hollow guitar attached to either side so that it looked familiar. Paul offered the design to Gibson, which showed no interest at the time.

It was a Californian radio repairman, Leo Fender, who turned the solid body into a mass-market product. Fender could not play the guitar well, but he understood manufacturing. His company's instrument of 1950 had a plain slab body, a neck attached with four screws rather than glue, and a pickup that could be replaced in minutes. It was cheap to build, easy to repair and loud. Named the Broadcaster, it was renamed the Telecaster in 1951 after another manufacturer objected that the name was too close to one of its own products.

Fender followed it in 1954 with the Stratocaster, which had three pickups instead of two, a contoured body and a metal arm that a player could use to bend the pitch of the strings. Gibson replied with its own solid instrument, developed with Les Paul and introduced in 1952. Both designs, with modifications, are still made today, and the arrangement of pickups, volume and tone controls that they established is still the standard.

Two further innovations shaped the sound. Single-coil pickups, the original design, were sensitive but also picked up a low hum from mains electricity and nearby lights. In the mid-1950s a Gibson engineer, Seth Lover, developed a pickup with two coils wound in opposite directions, which cancelled much of the hum; the humbucking pickup became standard on Gibson instruments. Meanwhile, guitarists discovered that valve amplifiers pushed beyond their intended operating level produced a distorted sound that many found expressive rather than faulty, and from the 1960s boxes were sold that created the effect deliberately.

Little about the electric guitar has changed fundamentally since. Digital modelling amplifiers and software now reproduce the sound of old equipment, yet the instrument itself remains a wooden body, a neck and a set of magnetic pickups. The reason may be that the electric guitar is not really an acoustic instrument at all: its voice is created by the chain of pickups, cables and amplifiers that follows it, and musicians have proved reluctant to abandon a chain they understand.

Every time a vehicle slows down, energy has to go somewhere. In a car with conventional friction brakes, pads press against spinning discs and the kinetic energy of motion becomes heat, which is carried away by the surrounding air. In heavy city traffic this happens hundreds of times on a single journey. The quantity wasted is considerable: a one-tonne car travelling at 50 kilometres an hour carries roughly 100 kilojoules of kinetic energy, about as much as would be needed to lift the same car ten metres off the ground. Regenerative braking is an attempt to capture part of that energy instead of throwing it away.

The trick relies on the fact that an electric motor and a generator are the same machine used in opposite directions. When current is fed to the motor, magnetic forces turn it and the vehicle moves. When the vehicle is slowing, the electronics rearrange the circuit so that the wheels drive the motor instead. A rotating magnet inside a coil of wire induces a current, and that current is directed into the battery. The resistance the motor offers to being turned is what slows the car, so no brake pads are needed while the system is working.

The physics imposes limits. Kinetic energy rises with the square of speed, so a vehicle moving at twice the speed carries four times the energy, and much of what can be recovered therefore comes from fast stops rather than gentle ones. Every conversion also loses something: the motor, the power electronics and the battery each take a share. In a well-designed electric car, between 60 and 70 per cent of the energy that would otherwise have been lost as heat can be returned to the battery and used again. It is on repeated stop-start journeys that the saving is greatest; at a steady motorway speed there is almost nothing to recover.

This is why regenerative braking never replaces friction brakes entirely. At very low speeds the generator turns too slowly to produce useful current, so the last few metres of every stop are handled by pads or shoes. A driver who has to stop suddenly needs far more braking force than the motor can supply, and an emergency stop remains the job of the friction system. Regeneration is also unavailable when the battery is already full, which is why some electric cars advise drivers to reduce the charge level before a long descent. Software blends the two systems so that the pedal feels the same whatever is happening beneath it.

Electric railways were the first large-scale users. A train that feeds current back into the line as it slows has been technically possible for a century, and many metro systems now do it routinely. The difficulty is what to do with the power. It can be used only if another train is drawing current nearby on the same section of line; if none is, it must be dumped as heat in resistors on the roof. Operators therefore design timetables so that trains accelerate and brake at the same time, and a few lines store surplus energy in banks of supercapacitors beside the track, ready for the next departure.

On the road, the technology reached a wide public through hybrid cars in the late 1990s and is now standard in electric vehicles. Because the motor begins slowing the car as soon as the driver lifts off the accelerator, many models offer a mode in which a single pedal is enough for most driving. So-called mild hybrids, which pair a small motor with a 48-volt battery, rely on regenerative braking for almost all of their modest fuel savings.

Where the recovered energy is stored matters a great deal. Batteries are heavy and accept charge at a limited rate, and that rate falls sharply in cold weather or when the battery is nearly full. Supercapacitors can absorb a burst of energy in seconds but hold much less of it. Engineers have therefore experimented with flywheels, which spin faster as energy is fed in, and with systems that use surplus power to compress air. The most promising research, however, is not about storage at all but about prediction: linking a vehicle's computers to satellite navigation and mapping data allows it to plan where to lift off the accelerator, how much energy to recover and what hill or junction lies ahead.

It is worth being honest about what regenerative braking can and cannot do. It does not generate energy; it recovers part of what would otherwise be lost. The motor, the power electronics and the battery add weight and cost, and that weight has to be carried everywhere, including on the open road where little is recovered. Claims made in manufacturers' advertising should be read in that light. The technology is at its most valuable where vehicles stop often and travel slowly — city buses, delivery vans, taxis and trains — and least valuable on the long motorway journeys that account for much of the mileage of a private car.

Few industries were changed as quickly by the smartphone as the restaurant trade. Since the first delivery platforms appeared in the 2000s, ordering a meal has become, for millions of people, a matter of a few taps. The platforms promised restaurants a new market without the cost of extra tables, and promised customers choice without leaving the sofa. The pandemic made them indispensable: when dining rooms closed, delivery was the only way many kitchens could sell food at all. Investors valued the largest platforms in the billions, and for a while it seemed that the industry had found a partner that would share both its risks and its rewards. What has become clear since is that the partnership is far from equal.

The arithmetic of a delivery order is the source of most of the argument. Platforms typically charge the restaurant a commission on each order, commonly between 15 and 30 per cent of its value, and often add fees for prominent placing on the app, for photography or for delivery itself. Restaurants, meanwhile, work on narrow margins: after rent, wages, energy and ingredients, a profit of five per cent of turnover is thought healthy in many markets. An order on which a third of the price disappears may therefore be sold at a loss, and restaurateurs describe the platforms, only half-jokingly, as a tax on their own customers.

The platforms reply, reasonably, that a commission buys something. An app puts a restaurant in front of people who did not know it existed, processes the payment, handles complaints and manages a courier. Its defenders argue that delivery orders are usually additional business rather than stolen business: without the app, that customer would have cooked at home. There is something in this, but the claim is difficult to test, and the platforms have little incentive to publish the figures that would settle it.

The deeper problem is not the commission but the customer. When a restaurant sells through an app it learns nothing about the person who ordered. It does not obtain an email address, cannot invite them back and cannot tell whether they liked the food. The platform, by contrast, knows all of it, and can use that knowledge to promote a rival, or a virtual brand of its own, to the same person the following week. Restaurants have discovered that a business can grow in volume while shrinking in independence.

Some of the cost is passed to the diner. It has become common for restaurants to set higher prices on delivery platforms than in the dining room, so that the same dish costs more when it arrives in a paper box. Diners tend to blame the restaurant rather than the app, which is one reason many owners are reluctant to raise prices and prefer to absorb the commission instead. Either way, somebody pays for the convenience, and it is rarely the platform.

The couriers are the most visible part of the system and the least secure. Most platforms classify them as self-employed, which means no sick pay, no guaranteed hours and no protection if they fall from a bicycle in the rain. Pay is calculated per delivery, and an algorithm decides which jobs are offered to whom and how quickly a rider must move to keep a good rating. Several jurisdictions have pushed back. Spain began requiring platforms to employ their riders in 2021, and courts elsewhere have reached similar conclusions, though the companies continue to contest them.

City governments have taken a blunter approach. During the pandemic, when restaurants were closed and delivery was their only income, several cities capped the commission that platforms could charge, among them New York and San Francisco. The companies argued that the caps were unlawful and would force them to raise prices for customers, and challenged them in court. Several of the caps were nevertheless made permanent, and they have become a model for other cities facing the same dispute. The episode showed how quickly a service that presents itself as a neutral marketplace can become an object of public regulation.

A quieter transformation has taken place behind the doors of commercial kitchens. Because a delivery order carries no atmosphere, no service and no view, one kitchen can produce several different restaurants from the same equipment. These virtual brands have no dining room and sometimes no sign in the street. They can be an efficient way to use spare capacity, and they allow a cook to test an idea cheaply. But they also allow a platform to compete with the restaurants that depend on it, and they make it harder for a diner to know who is actually cooking the food.

My own view is that the apps are neither the saviours nor the parasites that their supporters and critics describe. Delivery is a genuine service. The logistics of moving hot food across a city are harder, and more expensive, than they look. But a market in which one side holds the customer, the data and the terms of trade will not correct itself. The remedy is not to ban the technology. It is to insist on transparency: on what a commission actually buys, on who owns the customer's details, and on the employment status of the people who carry the food.