2024 Current ElectricityPower in Series and Parallel Combinations Medium Question 13 of 130 in Current Electricity

Two heaters A and B have power rating of 1 kW and 2 kW, respectively. Those two are first connected in series and then in parallel to a fixed power source. The ratio of power outputs for these two cases is:

A 1 : 2
B 2 : 3
C 1 : 1
D 2 : 9

The answer is D.

Solution

For a fixed source, the power in series: $P_S = \frac{P_1P_2}{P_1 + P_2} = \frac{1 \times 2}{1 + 2} = \frac{2}{3}$ kW Power in parallel: $P_P = P_1 + P_2 = 3$ kW $\frac{P_S}{P_P} = \frac{2/3}{3} = \frac{2}{9}$ So the ratio is 2 : 9.

Concept Ratio of power dissipated in series vs parallel heaters

Current Electricity in past papers

130 questions from this chapter have appeared across 27 exam years.