GCSE Physics resources

AQA GCSE Electricity

Current, Charge and Potential Difference

Current is charge flowing per second, while potential difference is the energy transferred per coulomb. Use Q = It and V = E/Q to connect the measurements to the particle and energy models.

AQA 8463AQA 8464 GCSE PhysicsCombined Science: Trilogy FoundationHigher

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The revision snapshot

Current is charge flowing per second, while potential difference is the energy transferred per coulomb. Use Q = It and V = E/Q to connect the measurements to the particle and energy models.

By the end, you should be able to:

  • Explain the quantities in a circuit.
  • Apply the electricity model, evidence or method to an unfamiliar exam context.
  • Recognise and correct this wrong turn: Putting a voltmeter in series.

Before you revise

Diagnostic question

Choose an answer from memory. Your result tells you what to watch for in the guide.

Current is…

Core revision guide

Learn the model, then use it

Current, Charge and Potential Difference questions become manageable when the central model, evidence and exam method are kept together. Read the explanation, test the misconception and then apply the idea without looking back.

The quantities in a circuit

Current is charge flowing per second, while potential difference is the energy transferred per coulomb. Use Q = It and V = E/Q to connect the measurements to the particle and energy models.

Build the physics picture

Current is not used up. It is the rate at which charge passes a point, so an ammeter goes in series. Potential difference is energy transferred per coulomb across a component, so a voltmeter goes in parallel with that component.

Relationships used in this guide

Charge flow: Q = It (C, A, s). Potential difference: V = E ÷ Q (V, J, C). Choose each relationship from the physical change described, convert quantities into compatible units and keep the unit beside the final answer.

A standard circuit places an ammeter in series and a voltmeter in parallel across a component.
Current is measured through the component; potential difference is the energy transferred per coulomb across it.Open the full-size exam diagram
Charge flowQ = ItC, A, s
Potential differenceV = E ÷ QV, J, C

Misconception clinic

Replace the tempting answer

Read each belief, say what is wrong with it, then compare your correction.

Tempting idea: Putting a voltmeter in series.

Use instead: Current is charge flowing per second, while potential difference is the energy transferred per coulomb. Use Q = It and V = E/Q to connect the measurements to the particle and energy models.

Tempting idea: Saying current is energy.

Use instead: Current is not used up. It is the rate at which charge passes a point, so an ammeter goes in series. Potential difference is energy transferred per coulomb across a component, so a voltmeter goes in parallel with that component.

Tempting idea: Leaving time in minutes in Q = It.

Use instead: Define the quantity, state its unit, name the meter and draw the correct series or parallel connection.

Retrieval practice

Quick checks

1. Which meter measures potential difference?

2. Which equation links charge, current and time?

3. Potential difference is…

4. In one series loop, current is…

5. Why is an ammeter in series?

Worked examples

See the method being built

These examples expose the difference between a secure the quantities in a circuit method and the common error “Putting a voltmeter in series.”.

Example 1 · Current from charge

120 C passes a point in 60 s. Calculate current.

  1. Use I = Q ÷ t.
  2. Substitute 120 ÷ 60.
  3. Give amperes.
Show the answer

I = 2.0 A.

Example 2 · Charge moved

A current of 0.40 A flows for 3.0 min. Calculate charge.

  1. Convert time to 180 s.
  2. Use Q = It.
  3. Substitute 0.40 × 180.
Show the answer

Q = 72 C.

Example 3 · Energy per charge

A 12 V supply transfers energy to 5.0 C of charge. Calculate the energy.

  1. Use E = VQ.
  2. Substitute 12 × 5.0.
  3. Give joules.
Show the answer

E = 60 J.

Exam precision

Exam technique: The quantities in a circuit

Do this: Define the quantity, state its unit, name the meter and draw the correct series or parallel connection.

Independent practice

Exam-style questions

Write an answer before opening the marking guidance. Then edit the exact phrase or step that would gain the next mark.

1. State the unit of charge.

[1 mark]
Show marking guidance and model answer

Marking guidance: Award one mark for the precise statement shown in the model answer.

Model answer: Coulomb, C.

2. A current of 2.5 A flows for 40 s. Calculate charge.

[3 marks]
Show marking guidance and model answer

Marking guidance: Award one mark for the correct relationship, one for a valid substitution and one for the final answer with its unit.

Model answer: Q = It = 2.5 × 40 = 100 C.

3. Explain why current is not used up by a lamp in a series circuit.

[3 marks]
Show marking guidance and model answer

Marking guidance: Award up to 3 marks for distinct physics points joined into a clear cause-and-effect chain.

Model answer: Charge is conserved, so the rate of charge flow is the same before and after the lamp.

4. Draw/describe where to connect a voltmeter to measure a lamp’s potential difference.

[2 marks]
Show marking guidance and model answer

Marking guidance: 2 marks are available for relevant, linked physics points that match the model answer.

Model answer: Connect it in parallel across the lamp.

5. A charge of 10 C gains 30 J in a cell. Calculate the cell’s potential difference.

[3 marks]
Show marking guidance and model answer

Marking guidance: Award one mark for the correct relationship, one for a valid substitution and one for the final answer with its unit.

Model answer: V = E ÷ Q = 30 ÷ 10 = 3.0 V.

6. State the difference between current and potential difference.

[1 mark]
Show marking guidance and model answer

Marking guidance: Award one mark for the precise statement shown in the model answer.

Model answer: Current is charge flow per second; potential difference is energy transferred per coulomb.

Questions pupils ask

Current, Charge and Potential Difference FAQs

What is the main idea in Current, Charge and Potential Difference?

Current is charge flowing per second, while potential difference is the energy transferred per coulomb. Use Q = It and V = E/Q to connect the measurements to the particle and energy models.

What mistake should I avoid in Current, Charge and Potential Difference?

Putting a voltmeter in series. Current is not used up. It is the rate at which charge passes a point, so an ammeter goes in series. Potential difference is energy transferred per coulomb across a component, so a voltmeter goes in parallel with that component.

Useful next steps

Connect this guide to your next task

I-V Characteristics Required PracticalReverse the power supply for negative potential differences and record pairs of current and potential difference. Use a suitable scale and explain the different curve shapes for a resistor, filament lamp and diode.Resistance and I-V CharacteristicsResistance is the ratio V/I for a component at a particular point. A fixed resistor is approximately ohmic at constant temperature, while a filament lamp and diode have non-linear current-potential difference relationships.How to Answer GCSE Physics Calculation QuestionsA reliable calculation answer is a short chain of decisions. Make the physics visible so a marker can award method marks even if arithmetic slips. More free PhysicsUK resourcesBrowse revision, practical and exam-support resources. Try AQA GCSE Physics in PhysicsUK Exam StudioApply your knowledge to marked exam-style work.