Why do RMS values change during rectification?

[Asad Raza]

Why RMS values change during half wave rectification, full wave rectification? And why does RMS value remain constant during smoothing?

 

[tech99]

Why RMS values change during half wave rectification, full wave rectification? And why does RMS value remain constant during smoothing?

The RMS voltage of a waveform is equal to a DC voltage providing the same heating effect.
So if we apply half wave rectification to AC, the current flows for only half the time and a DC voltage providing the same heating effect would be lower.
Smoothing can be of two types. If is capacitor input type, the output voltage is equal to the peak AC. Then the RMS value of the output DC is higher than that of the original AC. If it is "choke input type", the output voltage is the average of the input AC, and the RMS value of the output DC is a little lower then the RMS value of the original AC.

 

[sophiecentaur]

Why RMS values change during half wave rectification, full wave rectification?

RMS refers to the mean of the squares of the values. Half wave rectification gives zero for half of each cycle so the mean of the squares will be about half. The Power is just not being delivered for half the time.