View Single Post
hkhandrika
#1
Mar23-05, 10:17 PM
P: 15
The problem is:

The current I through the 4.0 k-ohm resistor in Fig. 26-42 is 6.50 mA. What is the terminal voltage Vba of the "unknown" battery? (There are two answers.)

The two answers depend on the direction of the current. Here is the picture:

http://home.san.rr.com/hkhandrika/26-42.gif

First I looked at the 4.0 k-ohm resistor and said that the 8.0 k-ohm resistor had 1/2 the current flowing thru it, then I added up the parallel resistors to get one that was (8/3)k-ohm with 9.75 mA of current going thru it.

I thought I could use this current and then say that the voltage at point B (if you go left) would be 9.75mA * the 8/3 resistor + 9.75 * the 5 k-ohm resistor. But then how would you figure out the voltage at point A? If you go right, could you then do 9.75mA * 8/3 resistor - 12V and set that equal to Va, and then add 9.75 mA * the 5 k-ohm resistor and say that's the voltage at B? I tried this, and my answer is incorrect. I am doing this on webassign so I can see whether my answer is wrong or not, but I dont have the solutions to this problem.

Am I doing the process correctly in the first place? Any help would be greatly appreciated.

Thank you for your time and effort.
Attached Thumbnails
26-42.gif  
Phys.Org News Partner Science news on Phys.org
Security CTO to detail Android Fake ID flaw at Black Hat
Huge waves measured for first time in Arctic Ocean
Mysterious molecules in space