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Activity 1: Sources of electric charges

Read the information and then answer the questions.

Sources of electric charges
Chemical cells (commonly called batteries)

A common source of electric charge is the torch battery. Strictly, a torch battery should be called a dry cell, not a battery. A battery is made up of a group of cells working together.

A torch battery contains a paste of chemicals, and is said to be a dry cell since it does not contain a liquid.

A common dry cell used in torches consists of a rod surrounded by a chemical paste in a metal case.

The chemicals in the paste keep taking electrons from the rod and giving them to the case. Electrons have a negative electric charge. Hence, there is a build-up of negative charge on the case. The rod becomes positive because it has lost negative electrons.

When the wires of the circuit are connected, the electrons can flow from the negative case through the circuit to the rod. Hence, there is a continuous current flow.

There are other dry cells besides the carbon/zinc cells. There are the alkaline cells, mercury and lithium cells. These are more expensive than carbon/zinc cells, but they supply a better source of electric charges.


Most of the electricity produced for households by the power stations comes from large generators. A generator uses magnetism to create electricity.


Certain crystals produce electricity when squeezed or stretched. Many gas barbecues are ignited using the piezoelectric effect. When the ignition knob is pushed or turned quickly, it squeezes a crystal that produces an electric spark that lights the gas for the barbecue.

Solar cells

Solar panel for a telephone
Solar panels generate electricity from light energy. Some calculators are powered by solar cells. In parts of Australia some telephones are powered by solar cells, as shown.

  1. Describe the structure of a torch battery or dry cell.
  2. Describe the flow of electrons to and from the dry cell in a circuit. You could do this by adding a wire to this diagram and showing the current flow using arrows.
    Dry cell
  3. Describe the other sources of electricity.
A battery is made up of a group of cells working together. What is an example of a true battery? How many cells do they have? Why is the car battery also called a wet cell?

If you put a piece of copper wire and a piece of zinc wire into a lemon and touch the wires with your tongue, you feel a tingle. This is a simple electrical cell. How does it work?

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