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JEE Main 2024 (31 Jan, Shift 2) · Electrical Power & Heating Effect

Electrical Power & Heating Effect question from JEE Main 2024 (31 Jan, Shift 2)

Q17JEE Main 2024 · 31 JAN · SHIFT 2Medium

Electrical Power & Heating Effect

By what percentage will the illumination of the lamp decrease if the current drops by 20%?

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Answer: (b)

  1. Illumination ∝P=I2R\propto P = I^2R, so P∝I2P \propto I^2.
  2. I′=0.8I⇒P′=0.64PI' = 0.8I \Rightarrow P' = 0.64P
  3. Decrease =1−0.64=0.36= 1 - 0.64 = 0.36, i.e. 36%. So the answer is (b).
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