Making electricity

Just as electricity can make magnetism, so magnetism can make electricity. A bicycle dynamo is a bit like an electric motor inside. When you pedal your bicycle, the dynamo clipped to the wheel spins around. Inside the dynamo, there is a heavy core made from iron wire wrapped tightly around—much like the inside of a motor. The core spins freely inside some large fixed magnets. As you pedal, the core rotates inside these outer magnets and generates electricity. The electricity flows out from the dynamo and powers your bicycle lamp.

The electric generators used in power plants work in exactly the same way, only on a much bigger scale. Instead of being powered by someone’s legs, pedalling furiously, these large generators are driven by steam. The steam is made by burning fuels or by nuclear reactions. Power plants can make enormous amounts of electricity, but they waste quite a lot of the energy they produce. The energy has to flow from the plant, where it is made, to the homes, offices, and factories where it is used down many miles of electric power cable. Delivering electricity this way can waste up to two thirds of the power originally produced!

Another problem with power plants is that they make electricity by burning "fossil fuels" such as coal, gas, or oil. This creates pollution and adds to the problem known as global warming (the way Earth is steadily heating up because of the energy people are using). Another problem with fossil fuels is that supplies are limited and they are steadily running out.

Photo: Making clean, renewable energy from the wind. Each of these giant turbines contains an electricity generator.

There are other ways to make energy that are more efficient, less polluting, and do not contribute to global warming. These types of energy are called renewable, because they can last indefinitely. Examples of renewable energy include wind turbines and solar power. Unlike huge electric power plants, they are often much more efficient ways of making electricity. Because they can be sited closer to where the electricity is used, less energy is wasted transmitting power down the wires.

Wind turbines are effectively just electric generators with a propeller on the front. The wind turns the propeller, which spins the generator inside, and makes a study current of electricity.

Unlike virtually every other way of making electricity, solar cells (like the ones on calculators and digital watches) do not work using electricity generators and magnetism. When light falls on a solar cell, the material it is made from (silicon) captures the light’s energy and turns it directly into electricity. Potentially, this means solar cells are an extremely efficient way to make electricity. A home with solar electric panels on the roof might be able to make most of its own electricity, for example.

The power of electricity

Before the invention of electricity, people had to make energy wherever and whenever they needed it. Thus, they had to make wood or coal fires to heat their homes or cook food. The invention of electricity changed all that. It meant energy could be made in one place then supplied over long distances to wherever it was needed. People no longer had to worry about making energy for heating or cooking: all they had to do was plug in and switch on—and the energy was there as soon as they wanted it.

Another good thing about electricity is that it’s like a common "language" that all modern appliances can "speak." You can run a car using the energy in gasoline, or you can cook food on a barbecue in your garden using charcoal, though you can’t run your car on charcoal or cook food with gasoline. But electricity is quite different. You can cook with it, run cars on it, heat your home with it, and charge your cellphone with it. This is the great beauty and the power of electricity: it’s energy for everyone, everywhere, and always.

Measuring electricity

We can measure electricity in a number of different ways, but a few measurements are particularly important.

A brief history of electricity

• 600 BCE: Greek philosopher Thales of Miletus (c.624–546 BCE) discovered static electricity.
• 1600 CE: English scientist William Gilbert (1544–1603) was the first person to use the word "electricity." He believed electricity was caused by a moving fluid called humor.
• 1733: French scientist Charles du Fay (1698–1739) found that there were two different kinds of static electric charge.
• 1752: American printer, journalist, scientist, and statesmen Benjamin Franklin (1706–1790) carried out further experiments and named the two kinds of electricity "positive" and "negative."
• 1780: Italian biologist Luigi Galvani (1737–1798) touched two pieces of metal to a dead frog’s leg and made it jump. This led him to believe electricity is made inside animals’ bodies.
• 1785: French scientist Charles Augustin de Coulomb (1736–1806) explored the mysteries of electric fields: the electrically active areas around electric charges.
• 1800: One of Galvani’s friends, an Italian physics professor named Alessandro Volta (1745–1827), realized "animal electricity" was made by the metals Galvani had used. After further research, he found out how to make electricity by joining different metals together and invented batteries.
• 1827: German physicist Georg Ohm (1789–1854) found some materials carry electricity better than others and developed the idea of resistance.
• 1820: Danish physicist Hans Christian Oersted (1777–1851) put a compass near an electric cable and discovered that electricity can make magnetism.
• 1821: A French physicist called Andre-Marie Ampère (1775–1836) put two electric cables near to one another, wired them up to a power source, and watched them push one another apart. This showed electricity and magnetism can work together to make a force.
• 1821: Michael Faraday (1791–1867), an English chemist and physicist, developed the first, primitive electric motor.
• 1830s: American physicist Joseph Henry (1797–1879) and British inventor William Sturgeon (1783–1850) independently made the first practical electromagnets and electric motors.
• 1831: Building on his earlier discoveries, Michael Faraday invented the electric generator.
• 1840: Scottish physicist James Prescott Joule (1818–1889) proved that electricity is a kind of energy.
• 1870s: Belgian engineer Zénobe Gramme (1826–1901) made the first large-scale electric generators.
• 1873: James Clerk Maxwell (1831–1879), another British physicist, set out a detailed theory of electromagnetism (how electricity and magnetism work together).
• 1881: The world’s first experimental electric power plant opened in Godalming, England.
• 1882: Thomas Edison (1846–1931) built the first large-scale electric power plants in the USA.
• 1890s: Edison’s former employee Nikola Tesla (1856–1943) promoted alternating current (AC) electricity, a rival to the direct current (DC) system promoted by Edison. Edison and Tesla battled for supremacy and, although Edison is remembered as the pioneer of electric power, it was Tesla’s AC system that ultimately triumphed.

DON’T play with electricity!

Electricity is useful—but it’s dangerous as well. The electricity that travels from power plants is thousands of times higher voltage and more dangerous than the electricity in our homes.

If you are silly enough to touch or play near power equipment, you could die a very painful and unpleasant death—electricity doesn’t just shock you, it burns you alive. Heed warnings like this one and stay well away.

The electricity that comes out of household power sockets is also dangerous enough to kill, so be sure to treat that with respect too. Don’t play with household power sockets or push things into them. Don’t take apart electrical appliances, because dangerous voltages can linger inside for a long time after they are switched off.

It’s generally safe to use small (1.5 volt) flashlight batteries for your experiments if you want to learn about electricity; they make relatively small voltages and electric currents that do you no harm. Ask an adult for advice if you’re not sure what’s safe.

It’s extremely important to be curious and to experiment—that’s what science is all about. But it’s also important to stay alive. If you’re not sure about anything electrical, be sure to leave it well alone.