# A.C. power supply voltage amplitude questions

• bluesteels

#### bluesteels

Homework Statement
The voltage across the terminals of an ac power supply varies with
time. The voltage amplitude is V = 45.0 V. What
are (a) the root-mean-square potential difference Vrms and (b) the average
potential difference Vav between the two terminals of the power supply?
Relevant Equations
Vmax= square root 2*Vrms
I know that the answer for A is 31.82. But when i look up B why is it zero? can someone explain please

thank you

Homework Statement:: The voltage across the terminals of an ac power supply varies with
time. The voltage amplitude is V = 45.0 V. What
are (a) the root-mean-square potential difference Vrms and (b) the average
potential difference Vav between the two terminals of the power supply?
Relevant Equations:: Vmax= square root 2*Vrms

But when i look up B why is it zero? can someone explain please
What do you think the answer to (b) should be?

Homework Statement:: The voltage across the terminals of an ac power supply varies with
time. The voltage amplitude is V = 45.0 V. What
are (a) the root-mean-square potential difference Vrms and (b) the average
potential difference Vav between the two terminals of the power supply?
Relevant Equations:: Vmax= square root 2*Vrms

I know that the answer for A is 31.82. But when i look up B why is it zero? can someone explain please
Look at a graph of (sinusoidal) alternating voltage vs. time. Can you use the graph to explain why the average is zero?

What do you think the answer to (b) should be?
i know that it zero cause i look it up but idk why

i know that it zero cause i look it up but idk why
No, what do you think it should be without looking it up. Without referring to any authority, what do you think it should be?

they didnt give me time?
Another way to ask the question is:
What is the average voltage over each complete cycle?​
Does that help?

Also, you might want to reply to @Orodruin's Post #6!