For the rectifier circuit shown in the figure, the expression for the average value of output voltage = __________, provided 'α' is the firing angle.
1
\(V_{0}=\frac{v_{m}}{4 \pi} \cos \alpha\)
2
\(V_{0}=\frac{2 v_{m}}{\pi} \cos \alpha\)
3
\(\mathrm{V}_{0}=\frac{2 v_{m}}{3 \pi} \cos \alpha\)
4
\(\mathrm{V}_{0}=\frac{v_{m}}{2 \pi} \cos \alpha\)