Full wave rectification using CTT and amplitude of output waveform

[PainterGuy]

Hello,

I did an experiment on full wave rectification using center tap transformer. The transformer read: Input 220V, Output 12V, 12V. I used two diodes and 1 micro farad capacitor. As you see capacitor's capacitance is very little so it didn't effect the overall output because I checked the output without using it. The peaks had amplitude of 18V. Shouldn't it be 12V or less? I connected oscilloscope across the resistor. Have a see on the the given diagram:

http://img233.imageshack.us/img233/4901/cttfullwaverectificatio.jpg

Help me out with this. Much grateful.

Cheers

 

[mdjensen22]

RMS vs. Peak
RMS = peak / √2
12 ~= 18/√2Edit:
http://en.wikipedia.org/wiki/Root_mean_square

 

[Jiggy-Ninja]

The capacitor will pull it down some as it smoothes the waveform

No it won't. The maximum value will stay 18 volts, it just won't dip all the way down to 0 in between alternations.

 

[mdjensen22]

You are correct. Not sure where my head was on that one...Sorry for the confusion.

 

[PainterGuy]

Many thanks, mdjensen22 and Jiggy-Ninja.

That means the value of the voltage given on the transformer label was RMS.

I used the formula, ripple factor=I_L/FC. I_L was almost 12.09 mA. I used the value of F as 60 Hz which was the frequency of AC source and the voltage of AC was 220V.

I think the instructor gave us the wrong formula because here on Wikipedia it seems Wiki is saying something different:
http://en.wikipedia.org/wiki/Ripple_(electrical)#Time-domain_ripple

Could you help me out with this please? Much grateful.

Cheers