Two bulbs marked 200 watt - 250 volts and 100 watt - 250 volts are joined in series to 250 volt supply. Power consumed in circuits is
- A. 33 watt
- B. 67 watt
- C. 100 watt
- D. 300 watt
Answer: B. 67 watt
Explanation: [Figure needs to be uploaded later]\n$P_1 = \frac{V_1^2}{R_1} \Rightarrow 200 = \frac{250^2}{R_1} \Rightarrow R_1 = 312.5 \Omega$. $P_2 = \frac{V_2^2}{R_2} \Rightarrow 100 = \frac{250^2}{R_2} \Rightarrow R_2 = 625 \Omega$. $R_{eq} = R_1 + R_2 = 937.5 \Omega$. $I = \frac{V}{R_{eq}} = \frac{250}{937.5} = 0.266 A$. Power consumed $= V \cdot I = 250 \times 0.266 = 66.67 \approx 67$ Watt.