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

Same current, shared voltage.

Six original Cambridge-style questions on series circuits: current the same everywhere, p.d.s adding to the supply, combined resistance, and full series calculations.

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 series rules that earn the marks

One current, voltages add, resistances add.

01
Recall
[2 marks]

State what happens to the size of the current at different points in a series circuit, and what happens to the p.d.s across the components.

  • The current is the same at every point. ✓
  • The p.d.s across the components add up to the e.m.f. of the supply. ✓
02
Calculation
[2 marks]

Three resistors of 2 Ω, 3 Ω and 5 Ω are connected in series. Calculate their combined resistance.

R = 2 + 3 + 5

R = 10 Ω

03
Calculation
[3 marks]

A 12 V battery is connected in series with a 2 Ω resistor and a 4 Ω resistor. Calculate the total resistance and the current in the circuit.

R = 2 + 4 = 6 Ω I = V ÷ R = 12 ÷ 6

I = 2.0 A

04
Calculation
[3 marks]

For the circuit in Question 3, calculate the p.d. across each resistor, and show that they add up to the supply voltage.

V₁ = IR₁ = 2.0 × 2 = 4 V V₂ = IR₂ = 2.0 × 4 = 8 V

4 V + 8 V = 12 V ✓

05
Analysis
[2 marks]

A third resistor is now added in series to the circuit in Question 3. State and explain what happens to the current.

  • The current decreases. ✓
  • Adding a resistor in series increases the total resistance, and since I = V ÷ R with V fixed, the current falls. ✓
06
Analysis
[2 marks]

Two lamps are connected in series with a cell. One lamp is unscrewed and removed. State what happens to the other lamp, and explain in terms of the circuit.

  • The other lamp goes out. ✓
  • There is only one path, so removing one lamp breaks the circuit and the current stops everywhere. ✓

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.