In the following circuit, the average voltage

$$ V_0=400\left(1+\frac{\cos \alpha}{3}\right) V $$

where $\alpha$ is the firing angle. If the power dissipated in the resistor is 64 W , then the closest value of $\alpha$ in degrees is

A single-phase $$SCR$$ based $$ac$$ regulator is feeding power to a load consisting of $$5\,\,\Omega $$ resistance and $$16$$ $$mH$$ inductance. The input supply is $$230$$ $$V,$$ $$50$$ $$Hz$$ $$ac.$$ The maximum firing angle at which the voltage across the device becomes zero all throughout and the $$rms$$ value of current through $$SCR,$$ under this operating condition, are

The triac circuit shown in figure controls the $$ac$$ output power to the resistive load. The peak power dissipation in the load is