SSC JE Electrical Engineering 23 Jan 2018 Morning Paper

Question : 150 of 200

Marks: +1, -0

Calculate the value of reactive power (in VAR) of a circuit having power factor of 0.8, when the apparent power of the circuit is 200 VA.

Solution:

Given
cos ϕ = 0.8
Apparent power S = 200 VA.
Now reactive power (Q) = S sin ϕ = 200 × sin ϕ
Now

\sin\ϕ=√{1-\cos^2\ϕ}

=√{1-0.8^2}

= 0.6
∴ Q = 200 × 0.6 = 120 VAR

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