Resistance of a light bulb
A 60 W bulb operates at 120 V. What is its resistance while operating?
Answer C: explanation for every choice
A
0.5 A is the current (P/V), not the resistance.
B
This is V/P, which doesn't give resistance.
C
Correct. P = V²/R, so R = V²/P = 14,400/60 = 240 Ω.
D
This multiplies voltage by power.
TakeawayP = IV = I²R = V²/R.
Equation usedElectrical power
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