Standard circuit diagram symbols

Figure 8 shows an electric kettle used to boil water.

The kettle is connected to the mains electricity supply by a three-core cable and plug.

Figure 9 shows the inside of the plug.

What are the colours of the insulation around the earth, live and neutral wires inside a plug?

Choose answers from the box.

The plug in Figure 9 contains a fuse.

What is the circuit symbol for a fuse?

Tick () one box.

The electric kettle contains a heating element.

The power of the heating element is 2420 W.

The current in the heating element is 11.0 A.

Calculate the potential difference across the heating element.

Use the equation:

The power of the heating element is 2420 W.

The current in the heating element is 11.0 A.

Calculate the resistance of the heating element.

Use the equation:

Kettle A and kettle B have the same total power input.

Kettle A has a greater efficiency than kettle B.

Which two of the following describe heating water in kettle A compared with kettle B ?

Tick () two boxes.

Figure 4 shows a student putting a coin into a vending machine that sells food.

The vending machine is connected to the mains electricity supply.

What is the frequency of the mains electricity supply in the UK?

Tick () one box.

What is the potential difference of the mains electricity supply in the UK?

Tick () one box.

The vending machine identifies the value of the coin by measuring the resistance of the coin.

The machine applies a potential difference of 0.45 V across the coin.

The current in the coin is 0.75 A.

Calculate the resistance of the coin.

Use the equation:

The temperature inside the vending machine is monitored using an electrical circuit.

Figure 5 shows part of the circuit.

The circuit symbol for the thermistor is wrong.

What is the circuit symbol for a thermistor?

Tick () one box.

How could the potential difference (pd) across the resistor be calculated?

Tick () one box.

At one temperature, the thermistor in Figure 5 has a resistance of 200 Ω.

What is the potential difference across the thermistor at this temperature?

Give a reason for your answer.

Tick () one box.

Figure 6 shows how the resistance of the thermistor varies with temperature.

When the temperature of the thermistor is 10 °C, the resistance of the thermistor is 600 Ω.

Calculate the change in resistance when the temperature increased from 10 °C to 15 °C.

An electrical appliance is connected to the mains electricity supply using a three-core cable.

Figure 13 shows a three-core cable.

What colour is the insulation covering the live wire inside the cable?

Tick () one box.

What colour is the insulation covering the neutral wire inside the cable?

Tick () one box.

The plug connected to the cable contains a fuse.

A fuse contains a wire that is designed to melt when the current is too great.

What is the circuit symbol for a fuse?

Tick () one box.

The wire in the fuse melts when there is a charge flow of 2.0 C in a time of 0.40 s.

Calculate the current in the wire when it melts.

Use the equation:

The mass of the wire is 0.016 g.

specific latent heat of fusion of the wire = 60 000 J/kg

Calculate the change in thermal energy needed to melt the wire.

Use the Physics Equations Sheet.

The fuse transfers some energy to the surroundings as it melts.

How does transferring energy to the surroundings affect the total energy needed to melt the fuse?

Tick () one box.

Figure 7 shows a student putting a coin into a vending machine that sells food.

The vending machine is connected to the mains electricity supply.

What is the frequency and the potential difference of the mains electricity supply in the UK?

The vending machine identifies the value of the coin by measuring the resistance of the coin.

The power dissipated by the coin is 340 mW when the current in the coin is 0.75 A.

Calculate the resistance of the coin.

Use the Physics Equations Sheet.

Coins that are dirty are not recognised by the vending machine.

Suggest one reason why.

Figure 8 shows part of a different circuit that is used to monitor the temperature inside

the vending machine.

The circuit symbol for a thermistor has not been included.

Draw the circuit symbol for a thermistor in the box below.

Figure 9 shows how the resistance of the thermistor varies with temperature.

The cooling system inside the vending machine turns on when the temperature of the thermistor is above 20 °C.

Determine the potential difference across the thermistor when the temperature is 20 °C.

Use the Physics Equations Sheet.

The live wire in a three-core cable is connected to a fuse inside a plug.

A fuse contains a wire that is designed to melt when the current gets too great.

Figure 17 shows a fuse.

What colour is the insulation covering the live wire in a three-core cable?

Draw the circuit symbol for a fuse in the box below.

The fuse wire melts when there is a charge flow of 2.0 C for 400 ms.

Calculate the current in the fuse wire.

Use the Physics Equations Sheet.

When the fuse wire is at its melting point, the additional energy needed to melt the wire is 1.02 J.

specific latent heat of fuse wire = 60 kJ/kg

Calculate the mass of the fuse wire.

Use the Physics Equations Sheet.

The calculation in Question 10.4 assumes there is no energy transferred to the surroundings.

How would the time taken for the wire to melt be affected if some energy was transferred to the surroundings?

Give a reason for your answer.

Tick (✓) one box.

A student investigated how the current in a filament lamp varies with the potential difference across the lamp.

Figure 1 shows the circuit used.

What is component P ?

Complete the sentences.

Choose answers from the box.

The ammeter in the circuit measures.

The voltmeter in the circuit measures.

How will increasing the resistance of the variable resistor in Figure 1 affect each of the following quantities?

Tick (✓) one box in each row.

A charge flow of 15 coulombs passed through the filament lamp in a time of 60 seconds.

Calculate the current in the lamp.

Use the equation:

When the current in the filament lamp is 0.12 A, the potential difference across the lamp is 6.0 V.

Calculate the resistance of the filament lamp.

Use the equation:

The student repeated the investigation after replacing the lamp with a resistor at constant temperature and then a diode.

The student plotted a graph for each component.

Draw one line from each component to its graph.

Figure 2 shows an ammeter.

The ammeter is not connected to a circuit.

What type of error does the ammeter display?

Tick (✓) one box.

A hair dryer contains three heating elements.

Figure 7 shows the circuit diagram for the heating elements in the hair dryer.

In Figure 7 the heating elements are represented by resistor symbols.

Complete the sentence.

Which switch must always be closed for the hair dryer to work?

Tick (✓) one box.

Which switches must be closed for the hair dryer to work at maximum power output?

Tick (✓) one box.

Use the Physics Equations Sheet to answer questions 06.4 and 06.5.

Write down the equation which links energy transferred (E), power (P) and time (t).

The heating elements have a maximum power output of 1200 W.

The energy transferred to the heating elements to reach normal operating temperature is 3600 J.

Calculate the time taken for the heating elements to reach normal operating temperature at maximum power output.

The hair dryer has LEDs to indicate the power setting.

What is the circuit symbol for an LED?

Tick (✓) one box.

Figure 12 shows some hair straighteners. Hair straighteners contain heating elements.

When the hair straighteners reach normal operating temperature, an LED turns on. Draw the circuit symbol for an LED in the box.

Figure 13 shows the circuit diagram for the hair straighteners. Each resistor represents a heating element. The power output of the hair straighteners can be changed by closing different switches.

The hair straighteners have a maximum power output of 120 W. The energy transferred to the hair straighteners to reach normal operating temperature is 3.6 kJ. Calculate the time taken for the hair straighteners to reach normal operating temperature when operating at maximum power. Use the Physics Equations Sheet.

Switch S₂ and switch S₃ are then closed at the same time. Explain what happens to the power output of the power supply.

A student heated water in an electric kettle.

Water has a high specific heat capacity. Complete the sentence. Choose answers from the box.

The specific heat capacity of a substance is the energy needed to raise the

The kettle circuit contains a thermistor which is used to switch the kettle off when the water reaches 100 °C. What is the correct symbol for a thermistor? Tick (✓) one box.

The resistance of the heating element in the kettle is 15 Ω. The current in the heating element is 12 A. Calculate the power of the heating element. Use the equation: power = (current)² resistance

The student investigated how quickly the kettle could increase the temperature of 0.50 kg of water. Figure 10 shows the results of the investigation.

The temperature of the water did not start to increase until 10 seconds after the kettle was switched on. What is the reason for this? Tick (✓) one box.

Describe a method the student could have used to obtain the results shown in Figure 10.

The mass of water in the kettle was 0.50 kg. The temperature of the water increased from 20 °C to 100 °C. specific heat capacity of water = 4200 J/kg °C Calculate the energy transferred to the water. Use the Physics Equations Sheet.

The water in the kettle boiled for a short time before the kettle switched off. During this time 5.0 g of water changed to steam. specific latent heat of vaporisation of water = 2 260 000 J/kg Calculate the energy transferred to change the water to steam. Use the Physics Equations Sheet.

A student investigated how the current in a filament lamp varied with the potential difference across the filament lamp. Figure 11 shows part of the circuit used.

Figure 11

Complete Figure 11 by adding an ammeter and a voltmeter. Use the correct circuit symbols.

Figure 12 shows some of the results.

The student reversed the connections to the power supply and obtained negative values for the current and potential difference. Draw a line on Figure 12 to show the relationship between the negative values of current and potential difference.

Write down the equation which links current (I), potential difference (V) and resistance (R).

Determine the resistance of the filament lamp when the potential difference across it is 1.0 V. Use data from Figure 12.

A second student did the same investigation. The ammeter used had a zero error. What is meant by a zero error?

Figure 13 shows an LED torch.

The torch contains one LED, one switch and three cells. Which diagram shows the correct circuit for the torch? Tick (✓) one box.

Write down the equation which links charge flow (Q), current (I) and time (t).

The torch worked for 14 400 seconds before the cells needed replacing. The current in the LED was 50 mA. Calculate the total charge flow through the cells.

When replaced, the cells were put into the torch the wrong way around. Explain why the torch did not work.

Write down the equation which links efficiency, total power input and useful power output.

The total power input to the LED was 0.24 W. The efficiency of the LED was 0.75 Calculate the useful power output of the LED.

A student investigated how the current in a filament lamp varied with the potential difference across the filament lamp. Figure 1 shows part of the circuit used.

Figure 1

Complete Figure 1 by adding an ammeter and a voltmeter. Use the correct circuit symbols.

Figure 2 shows some of the results.

The student reversed the connections to the power supply and obtained negative values for the current and potential difference. Draw a line on Figure 2 to show the relationship between the negative values of current and potential difference.

Write down the equation which links current (I), potential difference (V) and resistance (R).

Determine the resistance of the filament lamp when the potential difference across it is 1.0 V. Use data from Figure 2.

A second student did the same investigation. The ammeter used had a zero error. What is meant by a zero error?

Figure 3 shows an LED torch.

The torch contains one LED, one switch and three cells. Which diagram shows the correct circuit for the torch? Tick (✓) one box.

Write down the equation which links charge flow (Q), current (I) and time (t).

The torch worked for 14 400 seconds before the cells needed replacing. The current in the LED was 50 mA. Calculate the total charge flow through the cells.

When replaced, the cells were put into the torch the wrong way around. Explain why the torch did not work.

Write down the equation which links efficiency, total power input and useful power output.

The total power input to the LED was 0.24 W. The efficiency of the LED was 0.75 Calculate the useful power output of the LED.

Figure 9 shows a circuit diagram.

In which position could a switch be placed so that both lamps can be switched on or off at the same time?

Tick (✓) one box.

Draw the circuit symbol for a switch in the box below.

In 30 seconds, 24 coulombs of charge flow through the battery. Calculate the current in the battery. Use the equation:

There is a potential difference of 3.6 V across the battery. Calculate the energy transferred by the battery when 60 coulombs of charge flows through the battery. Use the equation: energy transferred = charge flow × potential difference

A student built Circuit X and Circuit Y shown in Figure 10. The components used in each circuit were identical.

Figure 10

Circuit X Circuit Y

How would the reading on the ammeter in Circuit Y compare to the reading on the ammeter in Circuit X ?

Tick (✓) one box.

How does the total resistance of Circuit Y compare with the total resistance of Circuit X ?

Tick (✓) one box.

The student built another circuit which is shown in Figure 11.

Write down the equation which links current, potential difference and resistance.

There is a potential difference of 3.6 V across the lamp in Figure 11. The current through the lamp is 0.80 A

Calculate the resistance of the lamp.

Draw a diagram to show how 1.5 V cells should be connected together to give a potential difference of 4.5 V.

Use the correct circuit symbol for a cell.

A student built the circuit shown in Figure 3.

Calculate the total resistance of the circuit in Figure 3.

Use the equation:

The resistance of P is 3.5 Ω.

Calculate the resistance of Q.

The student connects the two resistors in Figure 3 in parallel.

What happens to the total resistance of the circuit?

Tick one box.

Give a reason for your answer.

The plug of an electrical appliance contains a fuse.

What is the correct circuit symbol for a fuse?

Tick one box.

The appliance is connected to the mains electrical supply. The mains potential difference is 230 V.

Calculate the energy transferred when 13 C of charge flows through the appliance.

Use the equation:

energy transferred = charge flow × potential difference

Figure 9 shows the structure of a fuse.

Write down the equation that links charge flow, current and time.

The fuse wire melts when 1.52 coulombs of charge flows through the fuse in 0.40 seconds.

Calculate the current at which the fuse wire melts.

The mass of the fuse wire is 0.00175 kg. The specific latent heat of fusion of the fuse wire is 205 000 J/kg.

Calculate the energy needed to melt the fuse wire.

Use the Physics Equations Sheet.

A student investigated how the resistance of a piece of nichrome wire varies with length.

Figure 17 shows part of the circuit the student used.

Figure 17

Complete Figure 17 by adding an ammeter and a voltmeter.

Use the correct circuit symbols.

Describe how the student would obtain the data needed for the investigation.

Your answer should include a risk assessment for one hazard in the investigation.

Why would switching off the circuit between readings have improved the accuracy of the student’s investigation?

Tick one box.

A student investigated how the resistance of a piece of nichrome wire varies with length.

Figure 3 shows part of the circuit that the student used.

Complete Figure 3 by adding an ammeter and a voltmeter.

Use the correct circuit symbols.

Describe how the student would obtain the data needed for the investigation.

Your answer should include a risk assessment for one hazard in the investigation.

Why would switching off the circuit between readings have improved the accuracy of the student’s investigation?

Tick one box.