1. Power = voltage x current Current = power / voltage voltage = power / current 1.A 60 W lamp is connected to a 240V supply. What current does it take? Power= 60 W Voltage = 240V Current = ? 2.A kettle has a power rating of 2kW on the 230 mains. What fuse should be fitted in the plug?

2. Lesson Objectives To understand ‘earthing’ To know the differences between a fuse and a miniature circuit breaker To know the function of an RCD

3. Earthing appliances Appliances used in the U.K. are either metal on the outside or they are plastic. Metal ones are earthed. The earth wire is screwed on to the metal body of the appliance. The other end is connected down into the ground through a long brass rod. Earthing

4. Your Task Complete Sheet 1 - Earthing

5. Fuses and miniature circuit breakers (mcb) Circuit breakers act in the same way as fuses however they; respond quicker than fuses. are more sensitive. Unlike fuses which only operate once and need to be replaced a circuit-breaker can be reset.

6. A miniature circuit breaker The circuit breaker acts as a safety device in the same way as a fuse. It disconnects the supply if too large a current flows

7. Miniature Circuit Breaker An mcb does the same job as a ____, but in a different way. A switch is held in position by a spring. When the current becomes too _______ the circuit _______. The mcb acts much _____ than a fuse

8. If a fault occurs in the appliance some of the current will flow through the _____ wire. The amount of current flowing through the neutral wire decreases and now there is a difference between the _______ in the live and neutral wire. This difference is called the ______ current.

9. An electromagnetic switch responds to the difference in ______ and ______ the circuit.

10. Past paper Practise Jan 2009 Higher Tier Qu.doc