A coil has a inductance of 0.7H and is joined in series with a resistance of `220 Omega`. When an alternating emf of 220V at 50 cps is applied to it, then the wattless component of the current in the circuit is

Options

A. `5A`
B. `0.5A`
C. `0.7A`
D. `7A`

Answer

B

Explanation

Wattless component of current
`=l_(v)sin theta=(E_(v))/Z sin theta`
`=220/(sqrt(R^(2)+omega^(2)L^(2)))xx(omegal)/(sqrt(R^(2)+omega^(2)L^(2)))`
`=(220xxomegaL)/((R^(2)+omega^(2)L^(2)))`
`=(220xx(2pixx50xx0.7))/((220)^(2)+(2pixx50xx0.7)^(2))`
`=(220x220)/((220)^(2)+(220)^(2))=1/2=0.5A`