Electrical Safety : Good and Bad Practice

1.    When Lee’s new stereo arrived it did not have a plug on it. The only plug she could find in the house had a 13A fuse in it, so she used it. Stamped on the stereo case was 120W, 240V.

a)       Calculate the current that would flow to the stereo when it was switched on.                          [2]

b)       Would the stereo have worked when fitted with the 13A fuse ?                                                 [1]

c)       Would it have been a good idea to use this fuse ? Explain your answer.                                  [1]

2.    Jason bought his parents a new kettle for their anniversary. When he looked for a plug he could only find one with a 3A fuse. The kettle had a label with 2400W, 240V written on it.

a)       Calculate the current that would flow to the kettle when it was switched on.                           [2]

b)       Would the kettle have worked when fitted with the 3A fuse ?                                                    [1]

c)       Would it have been a good idea to use this fuse ? Explain your answer                                   [1]

3.   One night in Gareth’s house all the lights and downstairs plugs went off. When his mother investigated the fuse box she found that the 15A fuse wire had corroded. She didn’t have any spare 15A fuse wire so she used 3 pieces of 5A fuse wire twisted together instead (see diagram).

a)       Would this have worked ?                                                                                                                 [1]

b)       Would it have been a good idea ?                                                                                                    [2]

4.       When the lights in Millie’s house went out her father found that the 5A fuse in the lighting circuit had blown. He replaced it but it blew again so he used a 15A fuse instead. It blew as well so he used a 30A fuse and the lights stayed on.

a)       Would this have been a good idea?                                                                                                                                                           [1]

b)       Explain your answer to part (a).                                                                                                         [2]

5.       Copy and complete this table by filling in all the blank spaces

                                                                                                                                                                                [3]

6.       Earthing makes appliances safer to use.

a)       What type of appliances use an earth wire ?                                                                                  [1]

b)       Explain briefly how earthing makes an appliance safe.                                                                  [2]

Total marks [20]