# AQA P2.4

 What name is given to current that only flows in one direction? Direct current (dc) What sort of current is supplied by cells and batteries? Direct current (dc) What do the letters a.c. represent? Alternating current What is the period of an ac wave? The time for a complete cycle What is the relationship between the frequency (f) and the time period (T) of an ac wave? (T in seconds, f in Hz) How many volts is the UK mains supply? 230V What is the frequency of the UK mains supply? 50 Hz What does the unit Hz mean? The number of cycles per second How many pins does a normal UK mains plug have? Three What names are given to the three wires in a UK mains plug? LiveNeutralEarth What colour is the live wire in a UK mains plug? Brown What colour is the neutral wire in a UK mains plug? Blue What colour is the earth wire in a UK mains plug? Striped yellow and green Some mains cables only have two wires. Which wire is missing? Earth Which one of the 3 mains wires are circuit breakers and fuses always connected into? Live What happens to a fuse if the current exceeds the rating of the fuse? It melts, thereby breaking the circuit What do the letters RCCB represent? Residual Current Circuit Breaker Which safety device detects a difference in current between the live and neutral wires? RCCB Which acts the fastest, a fuse or an RCCB? RCCB Which appliances are usually earthed? Those with metal cases What does this symbol mean? Double insulated - (does not need an earth wire) What is the purpose of the earth wire? By providing a low-resistance path for the current to flow in the event of a fault, it enables the fuse to blow and break the circuit What is the link between an appliances cable thickness and its fuse value? The thicker the cable the larger the fuse value What happens when an electrical charge flows through a resistor? It gets hot In a filament lamp, what is most of the electrical energy converted into? Heat (wasted) What is the unit of power? Watt (W) What is the unit of energy? Joule (J) What is the unit of electrical current? Amperes (Amps) (A) What is the unit of electrical charge? Coulomb (C) What is the relationship between energy (E), potential difference (V) , and charge (Q) E = V x Q AuthorHLHSscience ID190963 Card SetAQA P2.4 DescriptionAQA Physics 2.4 Mains electricity Updated2013-01-01T12:06:50Z Show Answers