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## Main Question or Discussion Point

Hello again, I am having a bit of trouble understanding superimposed voltage.

Here is the problem:

A sinusoidal AC voltage source is in series with a DC source. Effectively, the two voltages are superimposed. Draw the total voltage across RL. Determine the maximum current through RL and the avg across RL.

Then there is a diagram.

The diagram starts with:

ground --> 200V DC --> 150Vpp AC --> R1 (47Ohm) --> RL (100 ohm) --> ground

I understand that the AC signal will be "increased" to a new peak voltage of 350V.

I understand that the AC signal will have a new low or 50V

What I am not sure about which method below (if either) is correct

1. Since the AC voltage never dips below zero again (due to the DC source) would the RMS value of the voltage simply be the DC source (200V)? Or, would I still calculate the RMS using the 150Vp (350 minus the new equilibrium base of 200V = 150Vp)?

2. Or, should I calculate the Vrms of the AC signal then simply add that value to the DC signal to get the "total voltage" in the circuit (since they are in series)?

I am not sure of the order of operations here. Do I combine the voltages then calculate? Or calculate then combine? Or neither?

I am having a lot of problems with this because the second part of the questions says find the "average voltage dropped across RL"). This statement implies that the voltage will still be alternating (otherwise there would be no average). This confused me because the method I used, was the Vrms which, with a superimposed DC signal of the 200V magnitude, would make it quite similar to the Vrms being dropped? I think?

I am not even sure I can word my question correctly because I am so confused. Sorry.

I am lost on how to do this problem (it wasn't assigned in class). When I asked my TA, he wasn't sure either (it was one of the challenge problems). I wanted to do it on my own, however, since I am struggling with RMS voltage (not understanding the exact point of using it if there is a DC source voltage present that increases the AC signal above zero).

Any insight would be great. Thank you!

Here is the problem:

A sinusoidal AC voltage source is in series with a DC source. Effectively, the two voltages are superimposed. Draw the total voltage across RL. Determine the maximum current through RL and the avg across RL.

Then there is a diagram.

The diagram starts with:

ground --> 200V DC --> 150Vpp AC --> R1 (47Ohm) --> RL (100 ohm) --> ground

I understand that the AC signal will be "increased" to a new peak voltage of 350V.

I understand that the AC signal will have a new low or 50V

What I am not sure about which method below (if either) is correct

1. Since the AC voltage never dips below zero again (due to the DC source) would the RMS value of the voltage simply be the DC source (200V)? Or, would I still calculate the RMS using the 150Vp (350 minus the new equilibrium base of 200V = 150Vp)?

2. Or, should I calculate the Vrms of the AC signal then simply add that value to the DC signal to get the "total voltage" in the circuit (since they are in series)?

I am not sure of the order of operations here. Do I combine the voltages then calculate? Or calculate then combine? Or neither?

I am having a lot of problems with this because the second part of the questions says find the "average voltage dropped across RL"). This statement implies that the voltage will still be alternating (otherwise there would be no average). This confused me because the method I used, was the Vrms which, with a superimposed DC signal of the 200V magnitude, would make it quite similar to the Vrms being dropped? I think?

I am not even sure I can word my question correctly because I am so confused. Sorry.

I am lost on how to do this problem (it wasn't assigned in class). When I asked my TA, he wasn't sure either (it was one of the challenge problems). I wanted to do it on my own, however, since I am struggling with RMS voltage (not understanding the exact point of using it if there is a DC source voltage present that increases the AC signal above zero).

Any insight would be great. Thank you!