Question

A coil has an inductance of 0.7 H and is joined in series with a resistance of 220 ohm. Find the wattless component of current in the circuit, when an alternating e.m.f. of 220 V at a frequency of 50 Hz is supplied to it.

Answer 1

`tan phi = (X_(L))/(R ) = (omega L)/(R ) = (2 pi xx 50 xx 0.7)/(220) = 1`
`:. phi = 45^(@), Z = sqrt(R^(2) + X_(L)^(2)) = sqrt(220 + 220^(2))`
`= 220 sqrt(2) Omega`
Wattless component of current `= I_(v) sin phi`
`= (E_(v))/(Z) sin 45^(@) = (220)/(220sqrt(2)) xx (1)/(sqrt(2)) = 0.5 A`