Physics Current Electricity ETEA 2018
PMDC Verified Question 93 of 112
A filament lamp has a resistance of 180\(\Omega\) when the current in it is 500mA. What is the power dissipated in the lamp?
A
45 W
B
90 W
C
290 W
D
360 W
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: 45 W
Concept:

Power dissipated by a resistive element can be calculated directly from current and resistance.

Formula:

$$ P = I^2 R $$

Solution:

  • Given Resistance \( R = 180 \, \Omega \).


  • Current \( I = 500 \text{ mA} = 0.5 \text{ A} \).


  • \( P = (0.5)^2 \times 180 = 0.25 \times 180 = 45 \text{ W} \).


Why other options are incorrect:

  • Opt B: Results from computing \( P = I \times R \) without squaring the current (0.5 * 180 = 90).


  • Opt D: Results from computing using \( P = 2 \times 180 \) (bad math or confusion).

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