A resistance `R` draws power `P` when connected to an `AC` source. If an inductance is now placed in series with the resistance, such that the impedence of the circuit becomes `Z`, the power drawn will be

Options

A. `Psqrt(R/Z)`
B. `P(R/Z)`
C. `P`
D. `P(R/Z)^(2)`

Answer

D

Explanation

`P=(V^(2))/R`

`P'=Vicos phi=V.V/Z.R/Z=V^(2)R/(Z^(2))`
`(P')/P=(V^(2)R//Z^(2))/(V^(2)//R)=(R/Z)^(2)`
`P'=P(R/Z)^(2)`