Q$1)$ The single$-$phase ac voltage controller has a $220$ V rms $50-Hz$ source. The series RL load has $R=18$ and $L=30mH.$ The delay angle $120.$ Determine $($a$)$ an expression for current, $($b$)$ rms load current, $($c$)$ rms current and voltage in each of the SCRs$,$ and $($d$)$ power absorbed by the load. $($e$)$ Sketch the waveforms of output voltage and voltage across the SCRs$,($f$)$ rms load current when $L=0mH.$