SIMPLE ELECTRIC CIRCUITS1.Let’s Change the Brightness of a Light bulbA simple electric circuit includes a cell, a bulb, a switch, and connection cables. These parts are called circuit components (one of the parts of something, especially a machine).

To light up a bulb in a simple circuit, all the components must work. The properties and values (importance) of the components in the circuit change the brightness of the light bulb. This means that the brightness of the light bulb changes in each circuit.

The brightness of bulbs in a simple circuit depends on the number of bulbs and the number of cells. As the number of bulbs in the circuit increases, each light bulb gets less energy. This means each light bulb shines less brightly.

Look at the circuits below. What are the differences between the brightness of the lamps? The first includes only one light bulb and one cell. In the second circuit there are two light bulbs. This makes both bulbs less bright than the bulb in the first circuit diagram.

As there are many light bulbs, the cell in the circuit may not have enough energy to light up the bulbs.

Let’s Change the Brightness of the BulbsYou need: 3-4 bulbs, connection cables, dry cells, switch.Preparation: 1. Set up a simple electric circuit. 2. Connect the bulbs one by one to the circuit and observe the changes in the bulbs.

Changing the Number of CellsIn this type of circuit, increasing the number of cells will make the light bulbs shine brighter. Decreasing the number of cells will make the bulbs less bright. When this happens, the bulbs are said to be dimmer(not bright). In the first circuit there is one cell and one light bulb. In the second circuit one more cell is added. So, the brightness of the light bulb increased.

Look at the brightness of the bulbs below

Let’s Change the Number of CellsYou need: 2 dry cells, connection cables, bulbs, switch. Preparation: 1. Set- up a simple electric circuit. 2. Connect the dry cells one by one to the circuit and observe the changes in the bulbs.

2. Electric Switches and Circuit SwitchesElectric appliances(a piece of electrical equipment) used in houses work with mains electricity(the place inside a building where you can connect a machine to a supply of electricity). Electricity is made in power stations and is brought to homes by thick(large) metal wires called cables.Electric energy is carried to cities through thick cables.

People use electricity by connecting the ends of these cables into electrical switches and sockets.

All electrical devices have a plug. This is fitted into an electric socket on the wall. In this way, the electrical devices are connected to the city electricity (mains supply).

Electric switches are placed on the walls to switch the lamps in the rooms on or off. When a switch is closed in a house circuit, the circuit is said to be completed. A complete circuit works.

3. Let’s Look at Circuit SymbolsThere are different types of circuit components. Each component has its own symbol that identifies it. Symbols are simple, easy to draw, take up little space and can easily be recognized. Circuit symbols are recognized and agreed on all over the world.The following table shows the symbols used for the components in simple circuits.

There are many different types of cells/batteries and light bulbs

Let’s Draw A Simple Circuit DiagramIn a circuit diagram, only circuit symbols are used. Pictures of the circuit components are not used. A circuit diagram is drawn by placing the positions of all circuit components in the right order, using their symbols. A circuit photograph is shown below; its circuit diagram is drawn below the photograph.

A photograph of another simple electric circuit made of two batteries, three bulbs, a switch, and connecting cables. Below the photograph is its circuit diagram.

Let’s Make Some Circuits WorkThere may be many reasons why a simple circuit doesn’t work or its light bulb doesn’t shine. Some of the reasons why circuits don’t work are explained below: -The bulb may be burnt out.-The cell may be used up. -There may not be enough cells in the circuit.-If the switch is open, the circuit has not been completed, so it won't work.-The light bulb may not be connected well in its socket.-If the wires are snapped(break) inside their covers, the circuit has not been completed.

Activity 11. A ................ is a circuit component that lights up. 2. The buttons you press to turn on radios and TV’s has the same function that a ................ does in a simple circuit.3. If the switch in a simple circuit is ................ the light bulb doesn’t light up.4. If the number of batteries is fixed in a circuit, but the number of bulbs is increased, the bulbs become ................ .5. If the number of bulbs is fixed in a circuit, but the number of batteries is increased, the bulbs become ................ .6. A ................ is shown by the symbol in a circuit diagram.7. Bulbs that are the same as each other are called ................ bulbs.8. In an electric circuit, the batteries are placed with their ................ poles connected.

Activity 2SIMPLE ELECTRIC CIRCUIT SYMBOLSThe circuit diagram below has incorrect symbols drawn on it. Re-draw the circuit diagram with the correct symbols.

Activity 3SIMPLE ELECTRIC CIRCUITMatch the correct circuit diagram to its photograph.

Activity 4 SIMPLE ELECTRIC CIRCUITSWrite T (true) or F (false) in the space at the start of the following statements.[......] 1. The symbols for electrical components change from country to country. [......] 2. A battery case is a box which can hold many cells. [......] 3. If the number of batteries in a circuit is fixed, while the number of bulbs is increased, the bulbs get dimmer. [......] 4. If the switch in a circuit is open the bulb doesn’t light up. [......] 5. A switch is shown by the symbol ( ) in a circuit diagram. [......] 6. If the number of bulbs in a circuit is fixed, while the number of batteries is increased, the bulbs get brighter. [......] 7. The light bulbs in your room work from the mains electricity supply. [......] 8. Electric buttons on the walls act in the same way as switches in simple circuits.

Activity 5 SIMPLE ELECTRIC CIRCUITLook carefully at the circuit diagrams below. Write down whether the bulbs light up or not, giving your reason.

Activity 6 SIMPLE ELECTRIC CIRCUITSLook at the circuit diagrams below and write down the number of circuit components present in each circuit.

Activity 7 SIMPLE ELECTRIC CIRCUITLook carefully at the electric circuits and draw their circuit diagrams, using symbols.

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