What is meant by alternating current ? Derive the expression for a sinusoidal e.m.f. induced in a coil rotating with uniform angular speed in a uniform magnetic field.

Explanation

Current that changes in its direction once in every half cycle is called as alternating currect.
Let Magnetic flux, `Phi =BAN cos omega t`
`e=(-dPhi)/(dt)`
`e=BAN omega sin omega t`.
i.e., `e=e_0 sin omega t , e/R=(e_0)/R sin omega t, i=i_0 sin omegat`
The direction of .e. is `+ve for Phi =0^@ "to" 180^@ ` and the induced current flows from X to Y and for `Phi =180^@ "to" 360^@` , the induced current flows from Y to X.

`e_(rms)=(e_(peak))/sqrt(2)`
where `" "e_(peak)=e_0=BAN omega`
B - Magnetic flux density,
A- Area of the conductor,
N - No. of turns.
`omega` - Angular frequency of rotation.