- #1

YoshiMoshi

- 228

- 8

on the homework help forums, please present the problem statement as text or LaTex and not as an image

## Homework Statement

Please see attached image 1 and image 2

## Homework Equations

## The Attempt at a Solution

Alright so I believe I solved part a correctly. It was very easy.

(A) 5 * phasor of 30 degrees

However it's been a while since I took circuits 1, so I'm struggling a bit with part (b). You can see my work in image 3 attached. For the phasor diagram for the voltage I drew IR as the reference along the positive x axis, IX point upwards, and the hypotenuse as ZI=V at an angle of 30 degrees from the reference. I believe this is correct?

I'm not exactly sure how to solve for the current here. I know ohms law V = IR, and I know that generally speaking we can write alternating current in terms of trigonometric functions, so the voltage as a function of time is something along the lines of

V(t) = A*sin(w*t + phase)

The problem specifies that it's at 60 Hz and I know that

w = 2*pi*f = 120*pi

So I know that the voltage is of the form

V(t) = 120*sin(120*pi*t + phase) volts

So

I = V/Z, but I can't seem to remember how to get the voltage into phasor form when I don't know the phase angle, hence I'm not sure how to draw the single phase diagram, or how to get the phasor current in this case. I guess I have a hard time putting the English into mathematical equation.

(C) I'm not exactly sure how to draw these graphs

For the voltage I drew the max as 120 volts, the min as -120 and I found the average as (2*max)/pi. I found this formula online, I believe it's correct?

I guessed that the current was in the form of 120/5 or 24 times some phasor

I(t) = 24 * phasor so I drew the max as 24 the min as -24 and used the formula for average above

For the power S I believe it's of the form sqrt(3)2880*some phasor

I don't see how to draw these graphs without given the initial phase angle of the voltage. Any help in solving either of these parts would be greatly appreciated. Thanks guys!