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P5 Electricity in the Home
1.
What type of supply is mains electricity?
a) dc
b) ad
c) cd
d) ac
2.
What is the frequency of the UK's domectic electricity supply?
a) 60 Hz
b) 50 Hz
c) 120 Hz
d) 230 Hz
3.
What is the potential difference of the UK's domectic electricity supply?
a) 50 V
b) 60 V
c) 120 V
d) 230 V
4.
What is the difference between a direct and an alternating potential difference?
a) A direct pd comes straight from the power supply.
b) An alternating pd is at a higher voltage.
c) A direct pd is transfers electrical energy where as an alternating pd does not.
d) An alternating pd changes direction where as a direct pd does not.
5.
What typr of cable is used to connet most electrical appliances to the mains supply?
a) 4 core
b) flex
c) 3 core
d) power chord
6.
Which gives the correct color coding for a UK mains cable?
a) live wire = red, neutral wire = black, earth wire = green and yellow stripes
b) live wire = red, neutral wire = blue, earth wire = green
c) live wire = brown, neutral wire = blue, earth wire = green and yellow stripes
d) live wire = blue, neutral wire = brown, earth wire = green and yellow stripes
7.
Which of the wires carries an alternating potential difference?
a) live and neutral
b) neutral
c) live and earth
d) live
8.
Which wires are at or close to earth potential?
a) neutral
b) earth
c) none
d) none
9.
Which wire only carries a current when there is a fault?
a) earth and neutral
b) neutral
c) earth
d) live
10.
Which wire is a safety wire to stop the appliance becoming live?
a) live
b) earth
c) neutral
d) earth and neutral
11.
Why is making a connection between live and earth wires a serious problem?
a) The appliance will be damaged.
b) It will increase the size of the bill.
c) It is not a problem - but it saves on wire.
d) It is not a problem - but it saves on wire.
12.
Why is connecting a light switch into the neutral wire of its circuit a problem?
a) It will not work.
b) Even when the light is switched off it ramains connected to the 230V supply.
c) It will stay on the whole time.
d) It will catch fire.
13.
Between which pair of wires is the potential difference 230 V ?
a) neutral and earth
b) red and black
c) live and neutral
d) blue and green
14.
Use the equation
power = voltage x current
to calculate the power of a 10 A 230 V mains outlet.
a) 23 W
b) 0.023 W
c) 230 W
d) 2300 W
15.
Use the equation
power = voltage x current
to calculate the current drawn by a 24 W bulb connected to a 12 V battery.
a) 288 A
b) 2.0 A
c) 0.5 A
d) 48 A
16.
Use the equation
power = voltage x current
to calculate the voltage needed to get a current of 10 A to flow through a 200 W heating element.
a) 20 V
b) 2000 V
c) 2 V
d) 200 V
17.
Calculate the power of a 20 W bulb with a current of 2 A passing through it.
P=I
2
R
a) 10 W
b) 20 W
c) 40 W
d) 80 W
18.
Calculate the power of a 10 W bulb with a current of 1 A passing through it.
P=I
2
R
a) 100 W
b) 10 W
c) 1 W
d) 0.1 W
19.
Calculate the resistance of a 100 W motor that draws a current of 5 A.
P=I
2
R
a) 4 Ohm
b) 20 Ohm
c) 500 Ohm
d) 60 Ohm
20.
Which of these best describes the work done by a power supply in a circuit?
a) Voltage is added to the current in the circuit.
b) The current is pushed around the circuit.
c) The current in the circuit is boosted.
d) Energy is transferred to the charge that flows through it.
21.
Which of these best describes the work done by a component in a circuit?
a) Energy is transferred from the charge that flows through it.
b) The component uses up some of the voltage.
c) The component uses up some of the current.
d) The component uses up the voltage and current.
22.
Which of these best describes the overall energy flow in a circuit?
a) The voltage transfers energy from the current to the component.
b) The component receives the electrical energy from the wires
c) Energy is transferred from the power supply to the component
d) There is no overall flow as the voltages cancel out.
23.
What term is used to mean the rate at which energy is transferred?
a) current
b) voltage
c) joules
d) power
24.
If a circuit transfers 25 J of energy to a bulb in 5 s which of the following is true?
a) The voltage of the bulb is 5 W
b) The current through the bulb is 5 A
c) The resistance of the bulb is 5 V/A
d) The power of the bulb is 5W
25.
What is the unit of electrical power?
a) Volt
b) Ampere
c) Watt
d) Coulomb
26.
Which of these is the same as 5W?
a) 5 J/s
b) 5 V/A
c) 5 J/C
d) 5 J/V
27.
What term refers to the system of cables and transformers linking power stations to consumers?
a) UK Power
b) Power Net
c) Network Power
d) Network Power
28.
What type of transformer is used to increase potential differrence ?
a) positive
b) upscaling
c) additive
d) step-up
29.
What type of transformer is used to decrease potential differrence ?
a) negative
b) downscaling
c) step down
d) subtractive
30.
Which type of transformer is used to connect the power station to the transmission cables?
a) step-down
b) step-free
c) quick-step
d) quick-step
31.
Which type of transformer is used to connect the transmission cables to consumers?
a) step-up
b) step-down
c) step-on
d) safe-step
32.
What is the point of the transformers used by the National Grid?
a) So power is transmittted at low voltages and high currents increasing efficiency.
b) So power is transmittted at high voltages and high currents increasing efficiency.
c) So power is transmittted at high voltages and low currents increasing efficiency.
d) So power is transmittted at low voltages and low currents increasing efficiency.
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