Q 12-03-009NEETNEET 2024Top questionMedium
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:
Answer: (D) $2:9$
With the same rated voltage $V$: $R_A = \dfrac{V^2}{1000}$ and $R_B = \dfrac{V^2}{2000}$.
Series: $R_s = R_A + R_B = \dfrac{3V^2}{2000}$, so
$$P_s = \frac{V^2}{R_s} = \frac{2000}{3}\ \text{W}$$
Parallel: the powers add, so
$$P_p = 1000 + 2000 = 3000\ \text{W}$$
$$\frac{P_s}{P_p} = \frac{2000/3}{3000} = \frac{2}{9}$$
Solution by Sreeraj P, M.Sc Physics