Starter quiz
- Which of the following types of circuit is used for car headlamps so that if one light stops working, the other stays lit?
- a series circuit
- a parallel circuit ✓
- either a series or a parallel circuit
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- Which of the following statements is correct?
- Voltage is measured in parallel, current is measured in series. ✓
- Both voltage and current are measured in parallel.
- Voltage is measured in series, current is measured in parallel.
- Both voltage and current are measured in series.
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- Which of the following statements about a circuit where a high current flows through a bulb and the voltage and current are correctly measured is correct?
- The voltmeter and the ammeter both have a high current passing through them.
- The voltmeter and the ammeter both have a low current passing through them.
- The voltmeter has a high current and the ammeter has a very low current passing.
- The ammeter has a high current and the voltmeter has a very low current passing. ✓
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In the circuit shown, what is the voltage across the electric cell if the voltage across the 8 resistor is 2.0 V and the voltage across the 4 resistor is 2.0 V?- 1.0 V
- 1.33 V
- 2.0 V ✓
- 4.0 V
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In the circuit shown, what will the ammeter read if the current in the resistor is 0.35 A and the current in the lamp is 0.25 A?- 0.25 A
- 0.30 A
- 0.35 A
- 0.60 A ✓
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- Where does our household electricity come from?
- only fossil fuel power stations
- only nuclear power stations
- wind turbines and solar panels
- hydroelectricity plants
- A mix of different sources, depending on weather conditions and demand. ✓
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Exit quiz
- Which of the following is the unit of power?
- ohms
- volts
- amps
- watts ✓
- joules
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- Which of the following devices or appliances has the greatest power rating?
lamp: 220-240 V, 50 Hz, 25W
loudspeaker: 50W
toaster: 220-240 V, 50/60 Hz, 860-1050W ✓
- How many watts are there in a kilowatt?
- a thousandth watts
- a thousand watts ✓
- a million watts
- a billion watts
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- Which of the following values is equal to 0.1 kilowatts?
- 1 watt
- 10 watts
- 100 watts ✓
- 1000 watts
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- How many watts are there in a gigawatt?
- 100
- 1000
- 1 000 000
- 1 000 000 000 ✓
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- What is the cost of using a 1000 W heater for 30 min, if 1 kWh costs £0.30?
- 3 pence
- 15 pence ✓
- 30 pence
- 60 pence
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Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- Electrical appliances and devices use different amounts of energy each second, as indicated by their power rating.
- Power is a measure of the amount of energy used by or supplied to a device in one second.
- Power is measured in watts (W).
- Multiplying power of a device in kilowatts (kW) by time in hours (h) gives us the energy used in kilowatt–hours (kWh).
- Electricity bills are based on the amount of energy units used; 1 unit of energy is equal to 1 kWh.
Common misconception
Most pupils do not discriminate sufficiently between current, voltage, energy and power.
Provide pupils with opportunities to calculate energy usage with appliances that have different power ratings and are used for different lengths of time.
Keywords
Power - the amount of energy transferred every second
Watts (w) - the unit of power
Kilowatts (kw) - a larger unit of power; 1 kW = 1000 W
Joules (j) - the unit of energy
Kilowatt–hours (kwh) - the unit of energy usage; 1 kWh = 1 unit of energy used
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