Question

If power dissipated in 5Ω resistor in 20W, then power dissipated across 4Ω resistor will be. 

(A) 1 W 

(B) 2 W 

(C) 3 W 

(D) 4 W

Answer 1

The correct option (D) 4 W

Explanation:

from figure, V = I₁ ∙ 5 = I₂ ∙ 10

∴ I₁ = 2I₂

Power decapitated = P = I²R

for 5Ω resistor, 20 = I₁² × 5

I₁² = 4

I₁ = 2A

∴ I₂ = (I₁ / 2) = (2/2) = 1A

∴ Power dissipated across 4Ω resistor = I_­2² × R

= 1² × 4 = 4 W