Single Phase Half Wave Silicon Controlled Rectifier with R Load, RL Load & RLE Load

Which of the following is control element in silicon controlled resistor (SCR)?
What is the average output voltage for half wave controlled rectifier for R load?
A single phase half wave controlled rectifier has 400 sin 314 t as the input voltage and R as the load, for a firing angle 60° for the SCR, the average output voltage is?
Name some of the current controlled (current driven) devices-
Thyristor can change the output voltage by modifying __________?