# Mains electricity

Flashcards by yusanr98, updated more than 1 year ago
 Created by yusanr98 over 6 years ago
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### Description

GCSE Physics Additional Science (AQA) Flashcards on Mains electricity , created by yusanr98 on 04/06/2014.

## Resource summary

 Question Answer What is it meant by direct current and alternating current? Direct current is in one direction only. Alternating current repeatedly reverses its direction. What do we mean by the peak voltage of an alternating potential difference? The peak voltage of an alternating potential difference is the maximum voltage measured form zero volts. What do we mean by the live wire and the neutral wire of a mains circuit? A mains circuit has live wire that is alternately positive and negative every cycle and a neutral wire at zero volts. How do we use an oscilloscope to measure the frequency of an alternating current? Frequency= 1 ____________________________ time taken for 1 cycle What is the casing of a mains plug or socket made from and why? Socket and plugs cases are made of stiff plastic materials that enclose the electrical connections. Plastic is used because it is a good insulator. What is in a mains cable? Mains cable consists of two or three insulated copper wires surrounded by an outer layer of flexible plastic material. What colour are the lives, neutral and earth wires? The live wire is brown, the neutral wires is blue, and the earth wire is green and yellow. Why does a 3-pin plug include an earth pin? The earth wire is connected to the longest pin and is used to earth the metal case of a mains appliance. Why is a fuse always on the 'live' side of an appliance? This cuts the appliance off from the live wire if the fuse blows. What is a circuit breaker? A circuit breaker is an electromagnetic switch that opens and cuts off the current if too much current passes through the circuit breaker. Why are appliances with plastic cases not earthed? A mains appliance with a plastic case does not need to earthed because plastic is an insulator and cannot become alive. What is the relationship between power and energy? The power supplied to a device is the energy transferred to it each second. How can we calculate electrical power and what is its unit? Electrical power supplied(watts)=current(amperes)*potential difference (volts) How can we calculate the current for a fuse? Correct rating (in amperes) for a fuse: electrical power (watts) =___________________________ potential difference (volts) What is an electrical current? An electrical current is the rate of flow of charge. How do you calculate charge from current and time? Charge (coulombs)=current (amperes)*time(seconds) What can we say about the electrical energy supplied by the battery in a circuit and the electrical transferred to the components? When charge floes round a circuit for a certain time, the electrical energy supplied by the battery is equal to the electrical energy transferred to all the components in the circuit. Why are electrical faults dangerous? Because they can cause electric shock and fires. How can we prevent electrical faults? Never touch a mains appliance with wet hands. Never touch a bare wire or a terminal at a potential of more than 30V. When choosing an electrical appliance, what factors in addition to cost should be considered? When choosing an electrical appliance, the power and efficiency rating of the appliance need to be considered.

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