Electrical charge and current

A hairdryer contains a heating element and a motor.

The motor is connected to a fan.

Figure 2 shows part of the electrical circuit inside the hairdryer.

How does the current in the motor compare with the current in the heating element?

Give a reason for your answer.

Tick (✓) one box.

The current is greater in the motor.

The current in both components is the same.

The current is less in the motor.

The potential difference across the motor is 20 V.

What is the potential difference across the heating element?

Give a reason for your answer.

Tick (✓) one box.

20 V 50 V
210 V
230 V

The hairdryer transfers 460 000 J of energy in 250 seconds.

Calculate the power of the hairdryer.

Use the equation:

The current in the hairdryer is 8.0 A.

Calculate the time taken for 1200 C of charge to flow past a point in the hairdryer circuit.

Use the equation:

The hairdryer is connected to the mains electricity supply.

What is the frequency of the UK mains electricity supply?

Tick (✓) one box.

50 Hz 60 Hz
100 Hz
230 Hz

A cordless hairdryer contains a heating element and a fan.

The hairdryer is powered by a rechargeable battery.

Figure 10 shows the cordless hairdryer.

The power output of the heating element is 0.24 kW when the potential difference across the heating element is 16 V.

Calculate the current in the heating element.

Use the Physics Equations Sheet.

The battery of the hairdryer can be recharged from 0 to 100% in 6.0 hours.

The power input to the battery is 18 W.

The potential difference across the battery is 24 V.

Calculate the charge flow through the battery in 6.0 hours.

Use the Physics Equations Sheet.

Figure 17 shows two different designs of wind turbine.

To generate electricity, the three-blade wind turbine rotates about an axis.

To generate electricity, the bladeless wind turbine oscillates from side to side.

Table 6 gives information about the two designs.

To generate electricity, the bladeless wind turbine oscillates from side to side.

Figure 18 shows the direction of the oscillations of the bladeless wind turbine.

Figure 19 shows how the power output of the bladeless turbine varies with the frequency of the oscillation.

Describe how the power output of the bladeless turbine varies with frequency.

The energy from wind turbines can be used to recharge a battery.

Use the Physics Equations Sheet to answer questions 10.3 and 10.4.

Which equation links charge flow (Q), current (I) and time (t)?

Tick (✓) one box.

Q = I t

Q = I² t

To fully recharge the battery, a charge of 216 000 C needs to flow through the battery.

The current in the battery is 5.0 A.

Calculate the time taken to fully recharge the battery.

Give the unit.

Figure 7 shows two different designs of wind turbine.

To generate electricity, the three-blade wind turbine rotates about an axis.

To generate electricity, the bladeless wind turbine oscillates from side to side.

Table 2 gives information about the two designs.

To generate electricity, the bladeless wind turbine oscillates from side to side.

Figure 8 shows the direction of the oscillations of the bladeless wind turbine.

Figure 9 shows how the power output of the bladeless turbine varies with the frequency of the oscillation.

Describe how the power output of the bladeless turbine varies with frequency.

The energy from wind turbines can be used to recharge a battery.

Use the Physics Equations Sheet to answer questions 03.3 and 03.4.

Which equation links charge flow (Q), current (I) and time (t)?

Tick (✓) one box.

Q = I t

Q = I t²

= I² Q t

To fully recharge the battery, a charge of 216 000 C needs to flow through the battery.

The current in the battery is 5.0 A.

Calculate the time taken to fully recharge the battery.

Give the unit.

A normal bicycle can be converted into an electric bicycle.

Figure 1 shows a converted bicycle.

Figure 2 shows the circuit diagram for the bicycle.

The circuit symbol for a motor is: M

The potential difference across the motor is 36 V.

The power output of the motor is 252 W.

Calculate the current in the motor.

Use the equation:

The bicycle battery can be recharged using the mains electricity supply.

A battery supplies direct current.

Mains electricity supplies alternating current.

Which graph shows an alternating current?

Tick (✓) one box.

A diode is used to change the alternating current to a direct current.

Which graph shows how the current in a diode varies with potential difference?

Tick (✓) one box.

The mean charging current from the mains is 5.0 A for 7200 seconds.

Calculate the charge flow to the battery.

Use the equation:

charge flow = current × time

Choose the unit from the box.

Calculate the work done in charging the battery when the power input is 1150 W for 7200 seconds.

Use the equation:

work done = power × time

The cable connecting the kettle to the socket is a three-core cable.

The insulation on each wire is a different colour.

Draw one line from each wire to the colour of insulation.

Use the Physics Equations Sheet to answer questions 06.3 and 06.4.

Which equation links charge flow (Q), energy (E) and potential difference (V)?

Tick (✓) one box.

The kettle is switched on to heat some water.

The energy transferred to the heating element in the kettle is 260 000 J.

The potential difference across the heating element is 1.3 V.

Calculate the charge flow in the heating element.

Figure 10 shows a step-down transformer that is part of a circuit inside a computer.

The transformer connects the mains supply to the computer circuit.

The potential difference across the primary coil is 230 V.

The potential difference across the secondary coil is 48.0 V.

The current in the primary coil is 2.40 A.

Calculate the current in the secondary coil.

Use the Physics Equations sheet.

The current in the primary coil is 2.40 A.

Calculate the time taken for a charge of 288 C to flow past a point in the primary coil.

Use the Physics Equations Sheet.

Give your answer in minutes.

Figure 11 shows the mains electricity circuit for the transformer.

An electrician replaced a faulty switch connecting the transformer to the mains supply.

The circuit was disconnected from the mains supply to prevent the electrician from receiving an electric shock.

Explain why the electrician could have received a shock if the circuit was connected.

Table 2 shows information about the effects of different electrical supplies on the human body.

ac is alternating current.

dc is direct current.

The mains electricity supply in the UK is ac with a frequency of 50 Hz.

Describe why it would be better if the UK mains supply was not 50 Hz ac.

Some security lights automatically switch on when it gets dark.

Figure 7 shows a security light.

Figure 8 shows part of a circuit that can be used to switch the security light on and off.

The circuit symbol for the LDR in Figure 8 is not correct.

Which is the correct circuit symbol for the LDR?

Tick (✓) one box.

The security light turns on when the potential difference across the LDR is 2.0 V

Determine the resistance of the LDR when the potential difference across the LDR is 2.0 V

Use Figure 8.

A charge of 3.24 C flows through the LDR in 40.0 minutes.

Calculate the current in the LDR.

Sometimes dirt can cover the LDR on the security light.

What effect would dirt on the LDR have on the security light?

Tick (✓) one box.

Some new cars have an electric motor that is powered by a battery.

A battery supplies direct current.

What is direct current?

Tick (✓) one box.

There are different types of battery available.

Table 2 shows the maximum distance a car can travel before the battery needs recharging.

Complete Figure 5.

You should:

• label the x-axis

• label the y-axis

• plot the data from Table 2.

A car with a lead-acid battery travels 80% of the maximum distance it can travel before the battery needs recharging.

Determine the distance the car travels.

A lithium-ion battery is put on charge for 1800 s

The current is 40 A

Calculate the total charge flow during this time.

Use the equation:

charge flow = current × time

The driver of a car saw an obstacle in the road. He applied the brakes until the car stopped.

The thinking distance was 9.0 m

The braking distance was 13.5 m

Calculate the stopping distance of the car.

The driver had been drinking alcohol. The car had worn brakes.

Explain why these factors would increase the stopping distance of the car.

A student investigated the motor effect.

Figure 9 shows the apparatus used.

The student closed the switch and the wire moved.

Explain why.

Give two ways of reversing the direction of the movement of the wire.

Electric motors use the motor effect.

Energy is supplied to the electric motor by a battery.

The battery is charged using a charger.

When the charger is connected to the battery, the potential difference across the battery is 15.0 V

The total energy stored when the battery is fully charged is 0.81 MJ

The average current used to charge the battery is 3.00 A

Calculate the time taken to fully charge the battery.

The charger is plugged into the mains electricity supply.

This is an alternating supply.

Give two other properties of the UK mains electricity supply.