Still having problem with these 2 >__<

Superceeded ( ignore everything below - kept for reference)

Superceeded2 (reference 2)



Superceeded questions below (for reference)

Q3
For V1 to be 0, the potential in between R1 and R2 must be the same as the potential between R3 and R4
Thus, R1/R2 = R3/R4
Hence, R4 = R3 * R2 / R1 = 86.89 ohms
Q4
I’m not very sure what is node to datum analysis. I use my
own method.
V1 = Vs = 9V
By Kirchoff’s Current Law,
(V1 – V2)/Ra = V2 / Rb + Is
(9 – V2)/10 = V2/4 + 3
V2/4 + V2/10 = 9/10 -3
V2 = -6V
Also, (V2 – V3)/Rc = Is
-6 – V3 = 30
V3 = -36V
I dun really understand what is meant by power supplied or absorbed by a current or voltage source...
here's an example similar to 1..
http://i105.photobucket.com/albums/m225/nickykeeng/album2/example1.png
dun worry about it though..
i will check the rest.. every time it's wrong i have a new question >__<
It's been a while since I last touched this.
Hope it's right!
Q1)
current is 1A throughout
clockwise:
voltage across resistor V=RI=14V (voltage drop)
voltage across Vs=3V (increase)
voltage across Is=11V (increase)
power given off by resistor = I2R=14W
power "absorbed" by Vs=VI=3W
power "absorbed" by Is=VI=11W
(not sure if my interpretation of absorb is right)
Question 3 was correct, my failed attempt at question 1 >__< 66%..

i need to re submit questions here again
absorted is something like having negative power due to opp current from power supply rite?
Q2)
Let the 10V thingy be Vs. 10ohm resistor be r10, 9ohm resistor be r9.
According to Kirchoff's current law, iunknown =0A
First look at the loop on the right.
current through r10=1A(anticlockwise)
voltage drop across r10=Ri=10V
Next look at the loop on the left.
current through r9=1A (anticlockwise)
voltage drop across r9=Ri=9V
voltage across Is1=19V
therefore power across Is1=Vi=19W
Originally posted by WoAiMeiMei:Question 3 was correct, my failed attempt at question 1 >__< 66%..
i need to re submit questions here again
Err... if u saw my answer for Q4, it was
9V, -6V and -36V respectively
You entered 9V, -36V and 36V
And erm... for question 1... if you can get the first 2, the final one must be such that the total power is 0. Conservation of energy still applies.
the trouble is finding the power across resistor for me >_<
resistors ALWAYS absorb power
oh lol mistake :x
Originally posted by WoAiMeiMei:the trouble is finding the power across resistor for me >_<
resistors ALWAYS absorb power
See Watershed's method for Q1. He's correct, but he used the previous values. You could try to apply it to the new values.
stress... sign convention is a killer
Q1.. R=39, V=6, -84?
Q2.. I (unknown) = -1 A
Q4.. V1=8 V2=1.25 V3=-0.75
ignore above >_<
thanks to ur method i got Q4 correct ^^
now got 2 more to work through.
Q1 - for some reason i cant get it fully correct.
Q2- is tricky