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If both the resistance and the inductance in an LR AC series circuit are doubled

If both the resistance and the inductance in an LR AC series circuit are doubled the new impedance will be

Options

(a) halved
(b) fourfold
(c) doubled
(d) quadrupled

Correct Answer:

doubled

Explanation:

For L-R circuit, Z = √(R² + Xʟ²)

Z₁ = √(R₁² + Xʟ₂²)

Z₂ = √(R₂² + Xʟ₂²)

Given, R₂ = 2R and Xʟ₂ = 2Xʟ

Then, Z₂ = √[(2R)² + (2Xʟ)²] = 2 Z₁

KL2013
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