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OCR GCSE Combined Science

Topic questions Electricity Direct and alternating potential difference

Direct and alternating potential difference

5 questions · 44 marks · about 50 minutes

Direct and alternating potential difference questions

TopicDirect and alternating potential difference

OCR J250 Direct and alternating potential difference 5 questions

Physics Paper 6 June 2025 Foundation tier, Question 16 12 marks

The diagram shows a power station connected to a town by the national grid.

Power Station Transformer Pylons and Wires Transformer
Town

Figure for question 16
(a)

The national grid uses alternating voltage.

A simple circuit powered by a battery uses direct voltage.

Explain the difference between alternating voltage and direct voltage.

[1]
Reveal mark scheme Mark scheme for question 16(a)
(b)

The table shows the current in one of the wires in the national grid at two different voltages.

Voltage across wire (V)Current in wire (A)
11 000730
400 00020
(b)(i)

The wire has a resistance of 2.0 maths symbol.

Calculate how much power is dissipated from the wire at 11 000 V.

Use the equation: power = current2 maths symbol resistance

Give your answer to 2 significant figures and in MW.

[4]
Reveal mark scheme Mark scheme for question 16(b)(i)
(b)(ii)

The national grid transfers 8 000 kJ of energy from the power station every second.

When the voltage across the wires is 400 000 V, the transformers and wires dissipate 160 kJ of this energy every second.

Calculate the efficiency of the energy transfer at 400 000 V.

Question 16, shown as an image
[3]
Reveal mark scheme Mark scheme for question 16(b)(ii)
(b)(iii)

Explain how step-up transformers allow the national grid to transfer energy more efficiently.

[3]
Reveal mark scheme Mark scheme for question 16(b)(iii)
(c)

A UK mains plug has 3 wires: live, neutral and earth.

Describe the function of the neutral wire.

[1]
Reveal mark scheme Mark scheme for question 16(c)

Physics Paper 12 June 2025 Higher tier, Question 11 12 marks

Figure for question 11
(a)

The national grid uses alternating voltage.

A simple circuit powered by a battery uses direct voltage.

Explain the difference between alternating voltage and direct voltage.

[1]
Reveal mark scheme Mark scheme for question 11(a)
(b)

The table shows the current in one of the wires in the national grid at two different voltages.

Voltage across wire (V)Current in wire (A)
11 000730
400 00020
(b)(i)

The wire has a resistance of 2.0 maths symbol.

Calculate how much power is dissipated from the wire at 11 000 V.

Use the equation: power = current2 maths symbol resistance

Give your answer to 2 significant figures and in MW.

[4]
Reveal mark scheme Mark scheme for question 11(b)(i)
(b)(ii)

The national grid transfers 8 000 kJ of energy from the power station every second.

When the voltage across the wires is 400 000 V, the transformers and wires dissipate 160 kJ of this energy every second.

Calculate the efficiency of the energy transfer at 400 000 V.

Question 11, shown as an image
[3]
Reveal mark scheme Mark scheme for question 11(b)(ii)
(b)(iii)

Explain how step-up transformers allow the national grid to transfer energy more efficiently.

[3]
Reveal mark scheme Mark scheme for question 11(b)(iii)
(c)

A UK mains plug has 3 wires: live, neutral and earth.

Describe the function of the neutral wire.

[1]
Reveal mark scheme Mark scheme for question 11(c)

Physics Paper 6 June 2018 Foundation tier, Question 13 6 marks

A student draws a diagram to show the national grid.

Figure for question 13
(a)

State the two mistakes in the diagram.

[2]
Reveal mark scheme Mark scheme for question 13(a)
(b)

The national grid uses transformers.

Explain how using transformers makes the national grid more efficient.

[2]
Reveal mark scheme Mark scheme for question 13(b)
(c)

Explain the difference between direct voltage and alternating voltage.

[2]
Reveal mark scheme Mark scheme for question 13(c)

Physics Paper 12 June 2018 Higher tier, Question 15 13 marks

The table shows some information about electrical appliances in the home.

AppliancePower (W)Current (A)Resistance ()
Electric drill8003.4866.1
Iron20008.6926.5
Kettle250010.8621.1
Security light5002.17105.8
Toaster16507.1732.1
(a)(i)

Use the table to describe the relationship between power and resistance.

[1]
Reveal mark scheme Mark scheme for question 15(a)(i)
(a)(ii)

Explain this relationship. Use ideas about resistance in your answer.

[2]
Reveal mark scheme Mark scheme for question 15(a)(ii)
(b)

The security light is switched on for 45 minutes every day for 7 days.

Use the equation: Energy transferred = Power × Time

Calculate the energy transferred in kWh.

Give your answer to 2 significant figures.

[4]
Reveal mark scheme Mark scheme for question 15(b)
(c)

Explain the difference between direct voltage and alternating voltage.

[2]
Reveal mark scheme Mark scheme for question 15(c)
(d)

The electric drill does not need an earth wire.

Explain why.

[1]
Reveal mark scheme Mark scheme for question 15(d)
(e)

Mains electricity can be produced in a power station that burns coal.

An electric iron is plugged into the mains and switched on. The temperature of the iron increases.

Describe this process.

Use ideas about energy stores in your answer.

[3]
Reveal mark scheme Mark scheme for question 15(e)

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Memes

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Revise all three sciences
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Me the night before the chemistry paper
Knowing it's three sciences
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Science enlightenment, combined

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all of them somehow

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Combined Science starter pack

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