The impedance of a circuit, when a resistance R and an inductor of inductance are connected in series in an AC circuit of frequency f is

Options

A. `sqrt(R+2pi^(2)f^(2)L^(2))`
B. `sqrt(R+4pi^(2)f^(2)L^(2))`
C. `sqrt(R^(2)+4pi^(2)f^(2)L^(2))`
D. `sqrt(R^(2)+2pi^(2)f^(2)L^(2))`

Answer

C

Explanation

In L-R circuit,
Impedance, `Z=sqrt(R^(2)+X_(L)^(2))`
Here, `X_(L)=omegaL=2pifL`
`therefore Z=sqrt(R^(2)+4pi^(2)f^(2)L^(2))`