Question

An alternating e.m.f. is given by `E=10 cos omega t`. If the frequency is 50 Hz, then at time `t=(1/600)s` the instantaneous value of e.m.f. is
A. 5 volt
B. 1 volt
C. 10 volt
D. `5sqrt(3)` volt

Answer 1

Correct Answer - D
`e = 10 cos (2 pi ft) = 10 cos [2pi xx 50 xx 1/600]`
`=10 cos (pi)/6 = 10 xx (sqrt3)/2 = 5 sqrt(3) V`.