Q147 / 270 · NDA 2023 (Phase 1) · General Ability

An electric bulb is rated as 220 V and 80 W . When it is operated on 110 V , the power rating would be :

  • A
    80 W
  • B
    60 W
  • Correct answer
    C
    40 W
  • D
    20 W

Solution

As, $\mathrm{P}=\mathrm{IV}$ Here, $\mathrm{v}_1=220 \mathrm{v}, \mathrm{p}_1=80 \mathrm{~W}$ and $\mathrm{v}_2=110 \mathrm{v}$ $\frac{p_2}{p_1}=\frac{v_2}{v_1}$ $\mathrm{p}_2=\frac{\mathrm{p}_1 \mathrm{v}_2}{\mathrm{v}_1}$ $=\frac{80 \times 110}{220}$ $\mathrm{p}_2=40 \mathrm{~W}$

Hence, the correct answer is option: 'C'.

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