Alternating Current - Result Question 26

26. A coil of inductive reactance 31Ω has a resistance of 8Ω. It is placed in series with a condenser of capacitative reactance 25Ω. The combination is connected to an a.c. source of 110 volt. The power factor of the circuit is [2006]

(a) 0.64

(b) 0.80

(c) 0.33

(d) 0.56

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Answer:

Correct Answer: 26. (b)

Solution:

(b) Power factor, ϕ=R(ωL1ωC)2+R2

=8(3125)2+82=862+82=810=0.8

Power factor =cosθ=RZ

For purely inductive and purely capacitive circuits, θ=90

Power factor =cosθ=cos90=θ For non-inductive circuit, θ=0 cosθ=cos0=1



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