The National Grid

Figure 11 shows how the National Grid connects a power station to consumers.

Complete the sentences.

Use the Physics Equations Sheet to answer questions 08.2 and 08.3.

Which equation links current (I), power (P) and resistance (R)?

Tick (✓) one box.

A transmission cable has a power loss of 1.60 × 10⁹ W.

The current in the cable is 2000 A.

Calculate the resistance of the cable.

Use the Physics Equations Sheet to answer questions 08.4 and 08.5.

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

The total energy input to the National Grid from one power station is 34.2 GJ.

The National Grid has an efficiency of 0.992

Calculate the useful energy output from this power station to consumers in GJ.

Figure 1 shows how the National Grid connects a power station to consumers.

Complete the sentences.

Use the Physics Equations Sheet to answer questions 01.2 and 01.3.

Which equation links current (I), power (P) and resistance (R)? Tick (✓) one box.

A transmission cable has a power loss of 1.60 × 10⁹ W. The current in the cable is 2000 A. Calculate the resistance of the cable.

Use the Physics Equations Sheet to answer questions 01.4 and 01.5.

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

The total energy input to the National Grid from one power station is 34.2 GJ. The National Grid has an efficiency of 0.992 Calculate the useful energy output from this power station to consumers in GJ.

Figure 8 shows how electricity is supplied to consumers.

Electricity from the power station can be generated using renewable or non-renewable energy resources.

Complete Table 2 to show which energy resources are renewable and which are non-renewable.

Tick (✓) one box in each row.

Transformers are used to make power transmission an efficient process.

Complete the sentences.

Choose answers from the box.

Each answer may be used once, more than once or not at all.

decreases the.

transfer from the overhead transmission cables to the surroundings.

The step-down transformer decreases the

Use the Physics Equations Sheet to answer questions 07.3 and 07.4.

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

The town of Hornsdale in Australia has electricity supplied by a huge battery.

The battery supplies a current of 130 000 A.

Calculate the charge flow from the battery in 5 minutes.

Choose the unit from the box.

Figure 8 shows how electricity is supplied to consumers by the National Grid.

Explain why transformer X is used in the National Grid.

Explain why transformer Y is used in the National Grid.

The town of Hornsdale in Australia has electricity supplied by a huge battery. On one day the battery transferred 3.24 × 10¹¹ J of energy to the town. The potential difference of the town’s electricity supply is 230 V. Calculate the charge flow to the town on this day. Use the Physics Equations Sheet. Give your answer to 3 significant figures.

Charge flow (3 significant figures) = C

Figure 2 shows part of the National Grid linking a power station to consumers.

Name the parts of Figure 2 labelled A and B.

Electricity is transmitted through A at a very high potential difference.

What is the advantage of transmitting electricity at a very high potential difference?

Tick (✓) one box.

The power station generates electricity at a potential difference of 25 000 V.

The energy transferred by the power station in one second is 500 000 000 J.

Calculate the charge flow from the power station in one second.

Use the equation:

The electricity supply to a house has a potential difference of 230 V.

Table 1 shows the current in some appliances in the house.

Calculate the total power of all the appliances in Table 1.

Use the equation:

power = potential difference × current

Each appliance in Table 1 is switched on for 2 hours.

Which appliance will transfer the most energy?

Give a reason for your answer.

The average energy transferred from the National Grid every second for each person in the UK is 600 J.

There are 32 000 000 seconds in one year.

Calculate the average energy transferred each year from the National Grid for each person in the UK.

Figure 13 shows some overhead power cables in the National Grid.

Explain the advantage of transmitting electricity at a very high potential difference.

It is dangerous for a person to fly a kite near an overhead power cable. Figure 14 shows a person flying a kite.

The person could receive a fatal electric shock if the kite was very close to, but not touching the power cable. Explain why.

A scientist investigated how the potential difference needed for air to conduct charge varies with the distance between a cable and earth. Figure 15 shows the results.

The data in Figure 15 gives the relationship between potential difference and distance when the air is dry. When the humidity of air increases the air becomes a better conductor of electricity. Draw a line on Figure 15 to show how the potential difference changes with distance if the humidity of the air increases.

Figure 16 shows a cross-section through a power cable.

A 1 metre length of a single aluminium wire is a better conductor than a 1 metre length of the steel wire. The individual wires behave as if they are resistors connected in parallel. Explain why the current in the steel wire is different to the current in a single aluminium wire.

Figure 1 shows how the National Grid connects power stations to consumers.

Name the parts of the National Grid labelled K, L and M.

Figure 2 shows how the percentage of electricity generated by gas-fired power stations changed in the UK over 5 years.

Calculate how many times greater the percentage of electricity generated by gas-fired power stations was in 2018 than in 2014.

Explain one environmental effect of generating electricity using a gas-fired power station.

The UK government wants more electricity to be generated using renewable energy resources. What is a renewable energy resource? Tick (✓) one box.

An offshore wind farm is a group of wind turbines that are placed out at sea. Figure 3 shows the power output of an offshore wind farm compared with a wind farm on land for a 24-hour period.

Give two advantages of the offshore wind farm compared with the wind farm on land. Use information from Figure 3.

Electric cars have motors that are powered by a battery.

Diesel cars have engines that are powered by diesel fuel.

Table 2 compares one type of electric car with one type of diesel car.

The electric car has a range of 400 km with a fully charged battery.

The diesel car has a range of 1120 km with a full tank of diesel.

Explain the difference in the time needed to complete a 500 km journey using the electric car compared with the diesel car.

Assume both cars travel at the same speed.

Energy density is the amount of energy stored per kilogram of the energy source.

Show why the diesel car has a greater range than the electric car.

Use data from Table 2.

Assume the efficiency of the two cars is the same.

Include calculations in your answer.

Engineers have developed a way of charging electric cars while they are driving along the road.

Coils of wire buried under the road transfer energy to the car’s battery as the car is passing over the coils.

Figure 6 shows a charging lane on a motorway.

Suggest two advantages of using this method to charge electric cars compared with plugging them into the mains electricity supply.

When electric cars are not being driven, energy stored in their batteries could be used to meet sudden peaks in electricity demand.

Suggest how.