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What is electricity?

We introduced static electricity in the previous topic and from this, you can understand that electricity is energy created by the movement of electrons. Unlike static electricity, other types of electricity flow quickly, which allow them to power electronic equipment. In this chapter, we explain how to control the flow of energy.

What is a circuit?

It is easier to use a source of energy when it has somewhere to go to and return. A circuit is a route designed to accommodate a flow of energy. A simple circuit requires three components: a power supply, a load and a conducting path.

Features of a circuit

The power supply, the source of energy that requires the circuit, may include sources such as a battery or any type of energy that can be harnessed as electricity including coal powered electricity, solar power, wind power and nuclear power.

A load is an object that uses the energy. It converts the power into another form of energy. A light bulb, for example, converts electricity into light and a fan converts electricity into motion.

The conducting path is the route that directs the energy from the source to the load and back to the source. In experiments, you will generally use wires to conduct the path of electricity. Good conductors are substances that allow the energy to flow easily.

Just like static electricity, electricity involves the movement of electrons. A power supply has a negatively charged terminal and a positively charged terminal. Excess electrons in the negative terminal flow through the circuit to reach the positive terminal.

Remember that unlike charges attract and like charges repel, so the negative terminal must always connect to a positive terminal for the electrons to flow. The circuit will not operate if you use two negative terminals or two positive terminals. Refer Image 1

A circuit operates when energy flows between the components without interruption. All parts must be connected for the circuit to operate. When one aspect of the circuit is disconnected, the circuit ceases to work. A switch is a device that allows us to connect and disconnect the flow of energy so we can control it. Although a switch is not a necessary component of a circuit, it is a useful addition so that you have some control of the electricity.

Representing circuits

To represent a circuit, scientists use a set of common symbols. Refer Image 2

Compare the image of a simple circuit with a switch with the diagram that represents the same thing. Refer Image 3

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Question 1/5

1. Which of the following is NOT a type of power supply?

nuclear power

a light bulb

a battery

solar power


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