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Home · IGCSE 0625 · Electricity and magnetism · Parallel circuits · Practice
Core · Practice questions · Parallel circuits

Currents that add.

Six original Cambridge-style questions on parallel circuits: branch currents adding to the main current, the same p.d. across each branch, lower combined resistance, and branch independence.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
The parallel rules that earn the marks

Currents add, voltage shared equally.

01
Recall
[2 marks]

State how the branch currents are related to the main current in a parallel circuit, and what is true about the p.d. across each branch.

  • The branch currents add up to the main current from the source. ✓
  • The p.d. across each branch is the same, equal to the supply. ✓
02
Calculation
[2 marks]

In a parallel circuit, two branches carry currents of 0.6 A and 0.9 A. Calculate the main current drawn from the supply.

I = I₁ + I₂ = 0.6 + 0.9

I = 1.5 A

03
Calculation
[3 marks]

A 12 V supply is connected to a 6 Ω resistor and a 4 Ω resistor in parallel. Calculate the current in each resistor and the total current from the supply.

I₁ = 12 ÷ 6 = 2 A I₂ = 12 ÷ 4 = 3 A

total I = 2 + 3 = 5 A

04
Analysis
[2 marks]

Two resistors are connected in parallel. State how the combined resistance compares with the smaller of the two, and explain why in terms of paths for the current.

  • The combined resistance is less than the smaller resistor. ✓
  • The parallel branches give the current more than one path, so more current flows for the same voltage, which means a lower resistance. ✓
05
Application
[2 marks]

Two lamps are connected in parallel across a battery. One lamp is unscrewed and removed. State what happens to the other lamp, and explain.

  • The other lamp stays lit (unchanged). ✓
  • Each branch is independent and still has its own complete path with the full supply voltage. ✓
06
Application
[2 marks]

Explain why the lamps and sockets in a house are connected in parallel rather than in series. Give two reasons.

  • Each device receives the full mains voltage, so it works at its proper rating. ✓
  • Each can be switched on or off independently, and if one fails the others keep working. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.