Electricity runs the TVs, air-conditioners, and other devices in our homes. Have you ever wondered where electricity comes from? Electricity actually comes from power stations far away from our homes. Electricity travels along very long power lines to reach our homes. There are different kinds of power stations that make electricity. For example, thermal power stations use heat energy to make electricity. Hydroelectric power stations use water power to make electricity.

The electricity made at power stations is very powerful. So the electricity’s strength is adjusted at substations before it reaches your home. The strength is lowered to a safe level of between 100 and 240 volts by the time it reaches your home.

Trains are very big and heavy. We know that electric trains move by electricity. But how do they work?

Fluorescent lamps light up our homes and classrooms. Fluorescent lamps come in different shapes and sizes. But when you turn on the switch, they all start to glow white after a few seconds. What makes them glow like that?

The middle of a fluorescent lamp is like a tube. When you turn on the switch, electricity travels through the space in the tube. The electrons collide with the mercury vapor inside the tube, which creates light. But people can’t see the light made by these collisions. This first light shines against the fluorescent material coated on the inside of the tube. The fluorescent material changes the light into light that we can see. This process is why it takes a few seconds for a fluorescent lamp to start to glow.

Have you ever played with a string telephone? You can make one by joining two paper cups with a tight string. If you talk into one of the cups, the other person can hear your voice in the other cup. But it’s impossible to talk to people far away with a string telephone. Walls get in the way, and the string can’t be super long.

When water is cold, the water molecules move slowly. When water is heated, the water molecules smash into each other. The energy produced by the collisions creates heat. So if you want to heat up food, you need to agitate the water molecules inside the food. This is where the microwave comes in. A microwave oven emits special electric and magnetic waves called microwaves. When these microwaves pass through the food, they cause the water molecules in the food to crash into each other. And that is why the food heats up.

How do toasters, irons, hair driers, and other appliances that heat up actually produce heat?

Appliances that produce heat contain special metal wires called nichrome wires. Electricity does not flow easily in nichrome wires. When electricity is forced to flow in nichrome wires, lots of heat is produced. Electricity flows when very tiny electric particles called electrons move among other small particles called atoms and molecules. But when these electrons try to move in a nichrome wire, where electricity does not flow easily, the electrons smash into the atoms and molecules in the nichrome wire. The energy produced when these collisions happen creates heat. So this is how toasters and irons get hot.

Clouds hold fragments of ice, both big and small. Each time the ice fragments crash into each other, some electricity is made. Little by little, this electricity is stored up in the cloud. When the cloud can’t hold all the electricity any more, the electricity suddenly flows in one big jolt toward the ground. This is how lightning works.

But have you wondered why we see flashes of light and hear loud rumbling sounds? In the instant that the electricity flows toward the ground, it heats up air molecules to very high temperatures over 10,000 degrees Celsius. This makes the air molecules move violently. The movement of air molecules causes the flashes of light and loud thunderclaps. Air normally does not let electricity pass through it. For lightning to happen, an enormous electric force of around 100 million volts builds up in the cloud. With this much force behind it, electricity pushes its way through the air and heads toward the ground. This is why we see lighting follow a zigzag path, rather than moving in a straight line.

There’s an amazing part inside a solar cell. When sunlight hits this part, it separates the electricity it makes between a part that gathers positive electric charges and a part that gathers negative electric charges. People were able to invent this amazing part, because electricity flows when negative electric charges are drawn toward positive electric charges.

In the similar way, doctors can figure out the condition of your body by the state of the electricity flowing in your body. For example, doctors use machines that measure electric signals in the brain called brain waves or electric signals created by heartbeats. The machines draw the signals as a picture called an electrocardiogram, or ECG. ECGs are useful because doctors can look at them and check for illnesses.

It’s amazing how TVs show our favorite programs on a screen every day. But how do images recorded in another place get to your TV?

When a TV station sends out images of a person, each picture is first cut into 525 lines. Then each of the lines is turned into the words of electricity, called electric signals. The electric signals are sent through the air from the TV station’s antenna. Your TV receives each of the lines one by one and then puts them in order from top to bottom to piece together the original picture. TV images are sent at a speed of 30 pictures every second. This is why the pictures appear to move on your TV screen.

Mobile phones work by changing your voice into an electric signal and sending that signal to the other person. But the electric signals are not sent directly through the air to the other person from your mobile phone. Electric signals from mobile phones can travel about 2 kilometers at most. So, the electric signals first travel to a base station within range of your mobile phone. Just like with regular telephones, telephone wires connect the base station to a base station near the other person. The base station near the other person sends the electric signals through the air to the other person’s mobile phone.

Your voice can be sent through the air either as an analog or digital electric signal. Mobile phones use digital electric signals. With digital electric signals, the vibrations in the air made by your voice are changed into numbers. Because they use numbers, digital electric signals can reach the other person without errors even in bad weather.

Before electric lights were invented, people used oil-burning lamps, candles, and gas lamps for light at nighttime. But these lights were not very bright. Then came the light bulb, which uses electricity to make bright light. The light bulb was invented by Thomas Edison, the king of American inventors. When electricity is forced to flow through a material that does not let electricity pass easily, that part of the material will emit heat and glow. The light bulb works on this principle. The problem was it was very hard to find a good material that does not let electricity pass easily. Materials that get hot and then burn are no good for a light bulb. Edison tried thousands of experiments trying to invent the light bulb. He found that bamboo grown in Japan was the best material for his light bulb, because it glowed without burning for a long time. In 1879, Edison at long last completed his light bulb! His powerful determination to never give up is what led to his success. An Englishman named Joseph Swan also researched light bulbs. Some say he invented the light bulb before Edison. In any case, Edison and Swan together set up a light bulb company and brought the light bulb to the world.

Electricity passes easily through metals like iron and copper. But electricity does not pass through wood, rubber, glass, and other materials. What is the difference that causes electricity to flow in some things, but not in others? The reason why electricity flows in copper wire and other metals is because metals have electrons that can move around freely inside them. These electrons are called free electrons. Batteries have an electric force inside them. So when a battery is connected to a metal wire, its electric force causes the free electrons inside the metal to move together in one direction. The free electrons move from the negative end of the battery to the positive end. This movement is the flow of electricity. On the other hand, wood, rubber, and other materials do not have a single free electron. That’s why electricity does not flow in these materials.

Objects are made up of many tiny particles called atoms and molecules. Atoms are connected together by even tinier particles called electrons. As you can see in the picture, several electrons spin in circles around the atom. It’s sort of like how the moon circles the earth. When atoms line up and form a molecule, the electrons start to move like bees flying back and forth between flowers.

But in metals, all the molecules are strongly connected together. This is why metals are hard. It’s also why electrons can fly around freely inside the metal. These electrons are called free electrons. Free electrons normally move around in all different directions. But when they move and flow in a certain direction, that movement becomes electricity. So if someone asks you “What is electricity?”, you can answer: “Electricity is the flow of tiny particles called electrons that move around inside a metal wire”. Such flows of electrons can happen naturally. For example, have you ever been surprised by a sparking sound when you try to open a door? That is a kind of electricity called static electricity. But static electricity happens only with a small part of an object and only lasts a very short time. So static electricity can’t be used to light a light bulb, for example. The electricity we use every day is dynamic electricity, not static electricity. In other words, we can’t use electricity that doesn’t continually flow in a fixed direction with a nearly constant force. Generators are what produce the electricity we need.

Have you read the What exactly is electricity? page? On this page, we’ll look at how electricity is generated. We will look at how to generate electricity that always flows in a fixed direction with a constant force. As we saw on the previous page, this type of electricity is useful for us. In 1831, an English scientist named Michael Faraday discovered the principle that makes electricity.

What about turning the coil rather than moving the magnet? When Faraday tried this, he found electricity was generated just like before. Turning the coil is much easier! But is there an even better way to make electricity? People around the world are always trying to answer this question by running many experiments. Because of these experiments, people have created many useful devices. Today, most large power generators produce electricity by spinning a coil inside a magnet. For example, think about a hydroelectric power station at a dam that you might see in the mountains. The dam partially blocks a river to raise the water level. When the water falls from the top of the dam, its force turns a special water wheel called a turbine. The turbine then spins the coil. That is how a hydroelectric power station works. At a thermal power station, coal or other fuels are burned to boil water. The force of the steam rising up from the boiling water turns a turbine. These days, you can often see wind turbines on cliffs and mountains. When their big blades turn, they also turn coils to generate electricity. In short, as long as you have a force to turn a coil, then you can generate electricity by nearly any means.