Formula for ripple factor in filter circuits

[iampaul]

i have come across two different formulas for ripple factor:
One is r= (Vrpp/Vdc), where Vdc is the dc voltage of the output and Vrpp is the peak to peak ripple voltage. My professor uses this formula and I have also seen it being used in basic electronics by Floyd
Another one is r= Vrms/Vdc from electronics by boylestad. Are these correct?

Is it possible to show that they are equivalent. Please help. Thanks in advance

 

[vk6kro]

They are not equivalent but Wikipedia shows them both as being used.

http://en.wikipedia.org/wiki/Ripple_(electrical)

So, it depends on your definition.

Peak to peak is easier to use and RMS would be difficult because the waveform is not sinusoidal.

 

[iampaul]

Thanks for the reply.