Question

Two 100 W heaters when connected in parallel across 220 V supply produced heat $Q_P$ in times t. If they are connected in series across the same power supply the heat produced in the same time is $Q_S$. What is $Q_P/Q_S$?

• A. 4
• B. 2
• C. 0.5
• D. 0.25

Answer 1

The correct option is A 4

In parallel, equivalent power $P_P=P_1+P_2=100+100=200W$

In series, the equivalent power, $P_S=\frac{P_1{P}_2}{P_1{P}_2}=\frac{100\times 100}{100+100}=50W$

Since, heat produced $=Pt$

So, $\frac{Q_P}{Q_S}=\frac{P_{P}t}{P_{S}t}=\frac{200}{50}=4$