The output current versus time curve of a rectifier is shown in the figure. The average value of output current in this case is

Iav=∫0T/2     i dt∫0T/2     dt=∫0T/2     I0sin(ω t)dtT/2=2I0T−cosω tω0T/2=2I0T−cos ωT2ω+cos0oω=2I0ω T[−cosπ+cos0o]=2I02π[1+1]=2I0π