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# Understanding Energy Conversion | Grade 7 Science Lesson

## Conversion Of Energy

Energy does not exist in one form alone. For daily use, we see a lot of examples of one form of energy being converted to another. The concept of energy conversion is very simple to understand. Try rubbing your hands together. What happens? Your hands are now warm, right? How did that happen? A moving object has kinetic energy. In this case, the two hands rubbing together moved together and thus had kinetic energy. That kinetic energy turned into heat energy. That is why your hands all of a sudden felt warm.

There are many other such instances when energy conversion happens in daily life. For example, you would have used matches to light a candle on a birthday party. What happens when you strike a match? The match head has chemical potential energy. When we strike a match, this chemical potential energy is converted into light energy and heat energy.

Similarly, what happens when you switch on a television? We know that the television uses electrical energy. So what happens is the electrical energy is converted into sound energy, light energy and heat energy. That is how we hear sounds, see images and feel that the television is warm after a while.

What happens when a fan is switched on? Of course the blades spin. Where do the blades get energy to spin? From electrical energy. So the electrical energy makes the blades spin and that provides kinetic energy which moves the air and create wind. The fan also gets hot after some time. So in this case, electrical energy turns into kinetic energy and heat energy.

Have you seen an electric bell? Most probably your school uses an electric bell. You would have noticed that it has a hammer and a gong. When the button is pressed the circuit is closed, and electricity passes through the circuit. This results in the hammer hitting the gong. Electrical energy from the battery is converted into kinetic energy and sound energy.

## Energy Converters

Are there devices that convert energy from one form to another? Of course, there are. Some of these energy converters produce electricity. Shall we look at some examples of energy converters?

### 1. Dynamo

Do you own a bicycle? Does it have a headlight? Without batteries, how does the headlight work? Well, the secret lies in a small device attached to the wheels of your bicycle. It is called a dynamo. So how does a dynamo carry out its very important job? When the bicycle wheels move, concurrently, the magnets in the dynamo spin. This spinning generates electrical energy.

### 2. Electric cells

How does a torch light work? By means of batteries, right? The components of a battery are electric cells. An electric cell is an energy converter. What does it do? It converts chemical potential energy into electrical energy. The electrical energy does not stay as electrical energy. If it stayed so, the torch will not light up. The electrical energy is converted into other forms of energy – in this case light energy.

### 3. Natural gas power station

At home, you flip a switch. A light turns on. Or a fan starts to turn. Or the television begins to work. How is all this possible? Electricity of course. It is power stations that generate large amounts of electricity that is needed in homes, schools and offices.

Alright. What happens in a power station?

• In the diagram above, do you see the natural gas supply entering a boiler via a pipe? There is a burner attached to the boiler. In the boiler, natural gas is burnt and heat is produced. This heats the water in the pipe into steam under high pressure. Thus, the conversion is from chemical potential energy of natural gas into heat energy of the steam.
• See the next stage of the process now. The steam spins the blade of the turbines. So in this case, the heat energy of the steam is converted into kinetic energy of the steam, which in turn is turned into kinetic energy of the turbines.
• The turbines are connected to a generator that converts the kinetic energy of the turbines into electricity. So in this case, the kinetic energy of the turbines is turned into electrical energy.

This process is repeated, and that is how electricity is generated by means of natural gas.