Kirchhoff’s second law tracks energy per charge
A complete circuit loop returns each charge to its starting point. Energy supplied per charge balances energy transferred per charge around the loop.
Follow the reasoning
- Choose a loop and a direction around it.
- Assign signs to sources and potential drops consistently.
- Combine the loop equation with junction equations if needed.
Try it in a past paper 6
Open the question, then use its mark scheme to check your work.
Question 3
Calculate resistance in a series-and-parallel network.
Build the supporting skills. Practise Series and parallel circuits before exploring this connection. This question has not been checked as a combined example of the connection.
Question 18
Calculate current for a cell with internal resistance.
Build the supporting skills. Practise E.m.f. and potential difference before exploring this connection. This question has not been checked as a combined example of the connection.
Question 3(b)
Calculate and evaluate the output of a thermistor potential divider.
Build the supporting skills. Practise Series and parallel circuits before exploring this connection. This question has not been checked as a combined example of the connection.
Question 4(a)
Compare the energy-transfer definitions of e.m.f. and potential difference.
Build the supporting skills. Practise E.m.f. and potential difference before exploring this connection. This question has not been checked as a combined example of the connection.
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Question 4(b)
Design a potentiometer experiment to compare cell e.m.f.s.
Build the supporting skills. Practise E.m.f. and potential difference before exploring this connection. This question has not been checked as a combined example of the connection.
Question 5
Find the resistance of a series–parallel network.
Build the supporting skills. Practise Series and parallel circuits before exploring this connection. This question has not been checked as a combined example of the connection.
A curated collection checked against the question papers and mark schemes; not a complete past-paper catalogue. Links open official OCR PDFs in a new tab.
Put the ideas to work
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Specification outcomes (4)
- 4.2.2(c) Distinguish between e.m.f. and p.d. in terms of energy transfer.
- 4.2.2(d) Use energy transfer equations W = VQ and W = EQ.
- 4.3.1(a) Apply Kirchhoff’s second law as conservation of energy in electrical circuits.
- 4.3.1(b) Apply Kirchhoff’s first and second laws to analyse electrical circuits.