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ELECTRICITY

BRIGHTER OR DIMMER
The objects below can be used to make a complete circuit. 
Battery
Bulb holder
Bulb
Connecting wires


The following electric circuit is a complete circuit.The bulb lights up because electricity flows through it.


A bulb is brighter when more electricity flows through it.More electricity flows in a circuit where more batteries are used.
A bulb becomes dimmer when the number of batteries in a circuit is reduced.

A bulb becomes dimmer when the number of batteries in a circuit is reduced.
Bulb C is very bright when three batteries are used in the circuit.
Bulb C becomes dimmer when only one battery is used.


A bulb becomes dimmer when more bulbs are added to the circuit.
Bulb D is bright.It is the only bulb in the circuit. ------>
 Bulb D becomes dimmer when another bulb is added to the circuit.
                              


EXERCISE ( 4a )




MATERIALS THAT CONDUCT ELECTRICITY
The bulb does not light up because the circuit is not complete.
The bulb lights up when an object that conducts electricity is used to complete the circuit.


Some materials allow electricity to pass through them.They are called conductors.Materials that conduct electricity are usually made of metals.Here are some objects that can conduct electricity.


Non-metals such as wood,plastic,glass,cloth and rubber do not conduct electricity.They are called non-conductor.Here are some objects that cannot conduct electricity.




EXERCISE ( 4b )




SWITCHES
A switch is used to complete or break a circuit.An electrical appliance is fitted with a switch so that it can be off when it is not in use.Let us take a look at some common switches 


The following bulb in the circuit does not light up.This is because the circuit is incomplete.


When A and B are connected with a steel spoon,the bulb lights up.This means that the steel spoon has completed the circuit.This shows that steel spoon can conduct electricity.