Potential Change in a Circuit Diagram

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SUMMARY

The discussion centers on calculating the potential at point Q in a circuit diagram where the potential at point P is given as 400 V. Using Ohm's Law (deltaV = iR) and the principle that the sum of potential changes in a loop must equal zero, the user determined the current (i) to be 20 A. By applying this current to the circuit, the potential at point Q was calculated to be 290 V after accounting for voltage drops across resistors.

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[SOLVED] Potential Change in a Circuit Diagram

Homework Statement


http://personalpages.tds.net/~locowise/test/28_29.gif

If the potential at point P is 400 V, what is the potential at point Q?


Homework Equations


Ohm's Law: deltaV=iR
Probably the fact that the sum of changes in potential in a loop of any circuit must be zero.

The Attempt at a Solution


Not real sure on this problem. I tried this:
150V - 2.0i - 3.0i - 50V = 0V and found i to be 20A.

I'm kind of puzzled and can't seem to relate the material in the textbook to this problem. Where does the 400V potential come into play? Thanks for your help!
 
Last edited by a moderator:
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I'm still not really sure this is the proper way to approach the problem but apparently the solution is correct. Here's what I did:

Used 20A from above.

400V - 50V - 3.0ohms * 20A = 290V
 

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