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