Electricity
Lesson overview
This lesson introduces the core physics idea, the useful equipment and the calculation or data skills used on this page.
What you will learn
Circuit data supplied on this page
Use these simple lamp and resistor examples to practise choosing between charge, current, potential difference and resistance.
Electricity and circuits infographic
Clear explanation
Current is the rate of flow of charge. A current of 2 A means 2 coulombs of charge pass a point each second.
Potential difference tells you how much energy is transferred by each coulomb of charge. A 6 V supply transfers 6 J of energy per coulomb.
Resistance describes how difficult it is for current to flow through a component. For an ohmic conductor at constant temperature, increasing potential difference increases current in proportion.
Key diagram
Worked examples
Charge passing through a lamp
A lamp has a current of 0.5 A for 20 s.
charge = current x time
charge = 0.5 x 20 = 10
Quick checks
Choose an answer, then check your thinking.
1. A current of 3 A flows for 4 s. How much charge passes a point?
2. What does potential difference measure in a circuit?
Practice questions
Question 1
A current of 0.2 A flows for 50 s. Calculate the charge transferred.
Reveal answer and marking guidance
Answer: 10 C.
Marking: Credit charge = current x time and 0.2 x 50 = 10 C.
Question 2
A resistor has 6 V across it and a current of 0.5 A through it. Calculate the resistance.
Reveal answer and marking guidance
Answer: 12 ohms.
Marking: Credit resistance = potential difference divided by current, so 6 ÷ 0.5 = 12 ohms.
Question 3
A component transfers 24 J of energy when 4 C of charge passes through it. Calculate the potential difference.
Reveal answer and marking guidance
Answer: 6 V.
Marking: Credit potential difference = energy transferred ÷ charge and 24 ÷ 4 = 6 V.
Question 4
In a simple series circuit, what happens to current at different points in the loop?
Reveal answer and marking guidance
Answer: The current is the same at every point in the series loop.
Marking: Credit the idea that charge is not used up by components.
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
- Saying current is used up by a component.
- Confusing charge with current.
- Using resistance = current divided by potential difference.
- Forgetting that volts describe energy transferred per coulomb.
Extension challenge
Make a three-column circuit table for charge, current and time. Fill in two values and calculate the missing value in three different rows.
Reveal answer
Example answer: A strong extension response names the physics model, uses accurate units and explains why the evidence supports the conclusion.
Exam-board guidance
Short board notes only. Learn the core physics above first.
AQA GCSE Physics
AQA GCSE Physics: often rewards clear physics explanations, correct equations, units and practical evidence for charge, current, potential difference and resistance.
OCR GCSE Physics
OCR GCSE Physics: often values precise definitions, clear working, graph interpretation and links between models and evidence.
Pearson Edexcel GCSE Physics
Pearson Edexcel GCSE Physics: often combines the concept with equation use, data handling and practical interpretation.
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: often expects accurate terms, units and evidence-based explanations using the shared physics idea.
CCEA GCSE Physics
CCEA GCSE Physics: connect the idea to your current unit and use the same practical method language your class uses.
Next lesson
Next, continue with Particles, Density and Internal Energy.