Mains electricity

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.

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

Figure 3 shows the three-core cable.

The insulation covering the earth wire has green and yellow stripes.

Give the colours of the insulation covering the live wire and the neutral wire.

A thermistor is used as part of a temperature sensor in the oven.

What is the circuit symbol for a thermistor?

Tick (✓) one box.

Figure 4 shows how the resistance of the thermistor in the oven varies with temperature.

Which statement describes the relationship shown in Figure 4 ?

Tick (✓) one box.

As temperature increases, resistance decreases.

As temperature increases, resistance stays the same.

As temperature increases, resistance increases.

Which temperature range shows the greatest decrease in the resistance of the thermistor?

Tick (✓) one box.

Between 50 and 100 °C

Between 100 and 150 °C

Between 150 and 200 °C

Between 200 and 250 °C

The resistance of the heating element in the oven is 5.0 Ω.

The current in the heating element is 12 A.

Calculate the power output of the heating element.

Use the equation:

power = (current)² × resistance

Calculate the energy transferred by the oven when 8000 C of charge flows through the heating element.

The potential difference across the heating element is 230 V.

Use the equation:

energy transferred = charge flow × potential difference

An LED on the oven is connected to an alternating current supply.

When the supply is switched on, the LED flashes on and off continuously.

Explain why.

Figure 9 shows a toaster.

A three-core cable connects the toaster to the mains electricity supply.

Which material could be used for the wires in the three-core cable?

Tick (✓) one box.

What is the potential of the earth wire?

Tick (✓) one box.

The wires and the cable are covered with a plastic material.

The plastic material covering each wire is a different colour.

Draw one line from each wire to the colour of the plastic material.

The plastic material covering the wires and cable is a type of polymer.

Explain how the plastic material acts as a safety feature if a person touches the cable.

When the toaster is switched on the current is 4.0 A

The resistance of the toaster is 60 Ω

Calculate the power of the toaster.

Use the equation:

power = (current)² × resistance

Give the unit.

Choose the unit from the box.

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.