Alternating Current. 0.0 / 5 ? PhysicsElectricityGCSEAQA Created by: cieran_10Created on: 24-06-18 20:38 What is direct current/d.c.? It is current which goes around a circuit in one direction, for example: the current supplied by cells and batteries. 1 of 11 What is a.c./alternating current? Current that repeatedly reverses its direction, for example: from the mains supply. 2 of 11 What is frequency? It is the rate that a.c. reverses its direction. 3 of 11 What is the frequency of the UK mains power supply and what does this mean? 50Hz (Hertz) This means that the current reverses its direction of flow 50 times every second. 4 of 11 How can the frequency of wire be calculated in practice? By mearuing the time taken for one full current cycle. 5 of 11 What does the live wire of a plug do? It alternates between postivie and negative with respect to the neatrual wire at 0V. 6 of 11 What peak p.d. does the live wire alternate between? +325V and -325V. 7 of 11 What is the live wire's a.c. p.d. eqivieltn to? 230V. 8 of 11 What is the National Grid? It is a system of cables and transformers linking power stations to concumers. 9 of 11 What are step-down tansformers? They are used to increase the p.d. from the power station to transmission cables. 10 of 11 What are step-up transformers? They are used to decrease the p.d. to a mucgh lower value for domestic use. 11 of 11
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