Smoothing of rectified voltage with capacitor

Andreasdreas

Okay guys

We are turning in the project today, so we cant make changes to the set up. We are asuming that the graphs was shifted compared to each other when it was meassured with the oscilloscope. The graphs was not emassured simultainously so the oscilloscope might have taken different zero points.

We have dropped the observations of the currents as the meassured currents was not sinusoidal, and the ammeter we used was set to meassure rms value of a sinusoidal current.

I just need to get one thing clear:
When the capacitor is charged by the rectyfied voltage (V_rec), it has some voltage betweeen its plates (V_c).
When the diode is reverse biased it is clear that only V_c contributes to the voltage over the lamp (V_L), but it is unclear to me what the situation is in the second half of the forward bias where v_rec is falling. From the attached graphes it is evident that the exponential behaviour if the red and orange graphs begins before V_rec reaches zero.
Is it true that that V_c+V_rec cannot exceed the maximum value of V_rec at any time?

sophiecentaur

As soon as the voltage of the source is below the volts on the capacitor, the capacitor will be discharging exponentially because there will be no charging current from the source (diode is reverse biased)
It is instructive to look at the time variation of the current delivered to the capacitor. Current only flows in short bursts of high value at the top of the AC cycle. The rest of the time it will be zero.

Studiot

This is a fundamental and crucial statement that you would be well advised to take note of.

I do not see that you have measured this effect from the data offered and you should have done. Perhaps a recommendation for the report?

I think we have done enough towards writing your report for you.

Go well in your studies.