In the circuit shown, there is a current of 3.0 A in the 2.0 Ω resistor.

Question 29

In the circuit shown, there is a current of 3.0 A in the 2.0 Ω resistor.

What are the values of the current I delivered by the power supply and the voltage V across it?

Reference: Past Exam Paper – November 2016 Paper 12 Q37

Solution:

Answer: C.

For the parallel section, the p.d. across each resistor is the same.

p.d. across 2.0 Ω resistor = IR = 3.0 × 2.0 = 6.0 V

The p.d. across the 6.0 Ω resistor is also 6.0 V.

Current through 6.0 Ω resistor = V / R = 6.0 / 6.0 = 1.0 A

Current I = 3.0 + 1.0 = 4.0 A

This same current flows through the 1.5 Ω resistor.

p.d. across 1.5 Ω resistor = IR = 4.0 × 1.5 = 6.0 V

e.m.f. V = 6.0 + 6.0 = 12.0 V