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By what percentage will the illumination of the lamp decrease if the current drops by 20%?
Asked in JEE Main 31st Jan 2nd Shift 2024 · Heating and power in resistors
- (1) 56%
- (2) 46%
- (3) 26%
- (4) 36%
Answer: (4) 36%
Step-by-step solution
Illumination ∝ P=I²R.
(P')/P=(0.8)²=0.64.
Decrease =36%.
Why the other options are wrong
- (1) No standard slip gives this; it would need the power to fall to 0.44 of its value.
- (2) No standard slip gives this; it would need the power to fall to 0.54 of its value.
- (3) No standard slip gives this; it would need the power to fall to 0.74 of its value.
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