Physics Unit 2 Revision (Higher tier)

When you know the period you can calculate the frequency (the number ofcycles per second)Most of your electrical devices are connected tothe mains supply by a cable connected to a threepin plug. The electrical cable is composed of acopper wire surrounded by a plastic insulator.The three pin plug consists of 3 separate wirescalled the Earth wire, Live wire and Neutral wire.The live and neutral wires are responsible forcarrying the electrical supply to and from themains supply.The voltage of the live wire (red line) alternatesbetween positive and negative and the neutral wire(blue line) remains close to zero. The earth pin isused for safety (in particular with devices that havea metal case) in conjunction with the fuse. If thelive wire happens to come in contact with the metalcase then you could get an electrical shock as thecurrent will pass through you to get to the ground. However, the earth wire andfuse prevents this from happening. The earth wire will take the current fromthe live wire. This high current then flows through the fuse wire causing it tomelt.Fuses and circuit breakersFuses have different current ratings. The fuse will blow if the current exceedsthis rating e.g. a 3 amp fuse will blow if the current is equal to or greater than3 amps. Most common fuse ratings are 3A, 5A and 13A.