PHYSICS CONNECTION
Kirchhoff’s first law conserves charge
Charge does not steadily accumulate at a junction in a steady circuit. The rates of charge entering and leaving must therefore balance.
ΣIin = ΣIout
Follow the reasoning
- Mark current directions at the junction.
- Add currents entering and leaving separately.
- Use the balance to find the unknown branch current.
OFFICIAL OCR QUESTIONS
Try it in a past paper 2
Open the question, then use its mark scheme to check your work.
Question 7
Connect a resistor network to internal resistance, drift speed, charge and dissipated energy.
Question 19
Use conservation of charge to find an unknown junction current.
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.
ORIGINAL PHYSICSUK QUESTIONS
Put the ideas to work
More practice is on its way
No PhysicsUK question linked yet. New eligible questions appear here as the bank grows.
Specification outcomes (4)
- 4.1.1(a) Define electric current as the rate of flow of charge, I = ΔQ / Δt.
- 4.1.1(g) Apply Kirchhoff’s first law as the conservation of charge at a junction.
- 4.3.1(b) Apply Kirchhoff’s first and second laws to analyse electrical circuits.
- 4.3.1(e) Analyse circuits with components including both series and parallel arrangements.