Electricity
This lesson builds circuit quantities and equations for GCSE Physics.
Use the core lesson first, then match the exam-board guidance to your school route. Many pupils meet this content through Combined Science as well as Separate Physics.
What you will learn
Exam-board fit
Exact paper labels and specification-point numbering vary by board and cohort, so match this lesson to your school route before using past-paper questions.
Circuit calculation set
Use the charge, energy and resistor data to practise selecting the correct equation before substituting.
Clear explanation
Circuit questions become easier when you identify the quantity being asked for before choosing an equation.
Current measures charge flow each second. Potential difference measures energy transferred per coulomb. Resistance compares potential difference with current.
Always keep units visible: amperes, coulombs, seconds, volts, joules and ohms tell you which equation fits.
Key diagram
Worked examples
Finding potential difference
A component transfers 48 J of energy to 8 C of charge.
potential difference = energy transferred ÷ charge
potential difference = 48 ÷ 8 = 6
Quick checks
Choose an answer, then check your thinking.
1. Which equation links charge, current and time?
2. A 4 V component has 2 A through it. What is the resistance?
Practice questions
Question 1
A current of 0.8 A flows for 30 s. Calculate charge.
Reveal answer and marking guidance
Answer: 24 C.
Marking: Credit Q = I t and 0.8 x 30 = 24 C.
Question 2
A charge of 5 C transfers 45 J. Calculate potential difference.
Reveal answer and marking guidance
Answer: 9 V.
Marking: Credit V = E ÷ Q and 45 ÷ 5 = 9 V.
Question 3
A resistor has 12 V across it and current 0.25 A. Calculate resistance.
Reveal answer and marking guidance
Answer: 48 ohms.
Marking: Credit R = V ÷ I and 12 ÷ 0.25 = 48 ohms.
Question 4
Why should you not say current is energy?
Reveal answer and marking guidance
Answer: Current is rate of charge flow; energy transferred is measured in joules.
Marking: Credit clear distinction between charge flow and energy.
Exam practice ladder
Answers and marking guidance
The exact practice answers are hidden under each question so you can try first. For this lesson, marks come from using the correct physics model, choosing the right equation where needed, keeping units with values, and explaining changes with precise words such as transfer, resultant force, acceleration, evidence and uncertainty.
Common mistakes
- Mixing up charge and energy.
- Using current = time divided by charge.
- Forgetting that V means joules per coulomb.
- Dropping units after calculation.
Exam-board guidance
All supported routes assess the core physics idea, but they may group topics, practicals and paper wording differently.
AQA GCSE Physics
AQA GCSE Physics: use this lesson for circuit quantities and equations, then check whether your class is taking Separate Physics or Combined Science.
OCR GCSE Physics
OCR GCSE Physics: the core physics idea is shared, but Gateway and Twenty First Century may organise questions differently.
Pearson Edexcel GCSE Physics
Pearson Edexcel GCSE Physics: practise the concept, the equation use and the practical language because questions often connect them.
Eduqas GCSE Physics
Eduqas GCSE Physics: learn the core explanation and practise applying it to unfamiliar contexts, data and practical questions.
WJEC Wales
WJEC Wales: check whether your class is using the current GCSE Physics route or a newer science route, then use this lesson for the shared physics idea.
CCEA GCSE Physics
CCEA GCSE Physics: connect the idea to your unit and remember that practical skills are assessed directly.
Extension challenge
Create three circuit equation triangles and write one original question for each equation.
Reveal answer
Example answer: A strong extension response names the physics model, uses accurate units and explains why the evidence supports the conclusion.
Next lesson
Next, continue with Series and Parallel Circuits.