Using Electricity
Just imagine for a moment a world without electricity.
At this precise moment electricity is driving your compter and probably your tv, lights and heating.

The picture on the left shows an electric meter which measures the amount of electrical energy we use up in our homes.
The units of energy are not Joules but the kilowatt hour.
One kilowatt hour is equivalent to the amount of electrical energy a 1kW appliance uses in one hour.

In this section of your Standard grade physics you will find out about what goes on behind the wall,what those small metal plates mean that are found on electrical appliances and what the difference is between ac & dc electricity

To help you study this section try these revision questions that appear below





  1. Gary`s hairdrier has the following metal plate attached to it:
    ratingplate a) How many wires are there in the flex of this hairdrier?
    b) What wire is missing and why is it not needed?
    c) What current does this hairdrier take from the mains?
    d) What size of fuse is required for the hairdrier?
    e) If the hairdrier was on for 3 minutes how many coulombs of charge would have passed through the hairdrier?


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  2. circuitCopy these circuit diagrams showing how you would measure the current which passes through bulb B1. Also show how you would measure the voltage across B1.


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  3. James & Helen have built this circuit in class. Find the value of the missing ammeter reading







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  4. circuit Salleem has built the following circuit in his Physics class. Find the missing voltmeter readings:






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  5. A bulb is rated as 6V and 0.006A. Calculate the power of the bulb.
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  6. Two resistors of value 20 ohms can be connected in series or parallel. What would be the values of the two possible combinations?
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  7. A kettle has a power rating of 2kW and draws a current of 10A. Calculate the resistance of the filament.
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  8. Sarah suspects that the fuse in her Granny`s iron has `blown`. Describe how she could build a continuity tester to see if the fuse had gone. Include a circuit diagram of the tester.
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  9. What are the advantages of the ring main circuit in your house?
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  10. A toaster is rated at 950W. Calculate the resistance of the element if the mains supply is 230V.
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  11. In the above toaster how much energy is used up in two minutes?
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  12. circuit In the circuit shown calculate the value of the variable resistance.
    If the resistance is increased what would happen to the current in the circuit?





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  13. On the picture of the electric meter at the top of the page(click here to see dial) you can see the units of energy are the kilowatthour.
    Calculate how many joules of energy there are in one kWh.


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