Cables and Plugs text book questions pg 67

1a Name the colour of each of the three wires in a mains plug.

• Red

• Blue

• Green

• Brown

• Yellow and Green

1bi Explain why sockets are wired in parallel with each other. Select 2.

• It makes the circuit more efficient

• It means each socket has the full p.d. of the mains across it.

• Each socket operates independently of the others so an open circuit at one socket doesn't stop the others from working.

2a Match the part with the material: 1 cable insulation

• Brass

• Copper

• Rubber

• Stiff plastic

2a Case

• Brass

• Copper

• Rubber

• Stiff plastic

2a Pin

• Brass

• Copper

• Rubber

• Stiff plastic

2a Wire

• Brass

• Copper

• Rubber

• Stiff plastic

For each material in part a, give two reasons for why this material is suitable.

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3a Explain why each of the wires in a three-core mains cable is insulated.

• To keep them warm

• To keep them cool

• To prevent electrical connection between them inside the cable

3b Describe how the metal case of an electrical appliance is connected to earth. Select 3.

• A electrical wire is attached to the metal case.

• This wire is connected inside the appliance so that it is connected to the top pin of the plug.

• This wire is connected inside the appliance so that it is connected to the same pin as the blue wire in the plug.

• The earth cable from the plug is ultimately connected to a thick copper rod which is dropped into the ground near to the property.

• The earth cable from the plug is ultimately connected to the 'zero' p.d. at the power station.

4a Explain why the cables joining the wall sockets in a house need to be thicker than the cables joining the light fittings. Pick 2.

• Sometimes the appliances plugged in might draw more current than light fittings.

• Light fittings always need more current than appliances that are plugged in.

• When more current is needed thicker cables are required in order to lower the resistance and reduce power loss and heating.

• When more current is needed thinner cables are required so the current goes faster

• When less current is needed thicker cables are required to make sure they stay cool.