Thyristor $T_{1}$ is triggered at an angle $\alpha$ (in degree), and $T_{2}$ at angle $180^{\circ}+\alpha$, in

each cycle of the sinusoidal input voltage. Assume both thyristors to be ideal. To

control the load power over the range $0$ to $\text{2 k W}$, the minimum range of variation

in $\alpha$ is:

1. $0^{\circ}\:to\:60^{\circ}$
2. $0^{\circ}\:to\:120^{\circ}$
3. $60^{\circ}\:to\:120^{\circ}$
4. $60^{\circ}\:to\:180^{\circ}$
in new
edited