An alternating current of frequency `'f'` is flowing in a circuit containing a resistance `R` and a choke `L` in series. The impedence of this circuit is

Options

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

Answer

B

Explanation

`X_(L) = omega L = 2 pi f L `
`Z = sqrt(R^(2) + X_(L)^(2)) = sqrt(R^(2) + 4 pi ^(2) f^(2) L^(2))`