Finding the current through each of the resistors

[november1992]

Homework Statement

I need help with this problem. I would appreciate it if you could explain how you got your answer.
thanks!

In the diagram below, what are the currents in each of the resistors? Show how you arrived at your answer.

[PLAIN]http://img801.imageshack.us/img801/6237/unledoer.png

Homework Equations

V=IR? I'm not sure if this is a parallel circuit. I'm guessing if it were Is = Vs/R1 +Vs/R2 + Vs/R3

The Attempt at a Solution

I really don't know where to start.

 

[NascentOxygen]

If current is able to flow (remember, it goes from the +ve terminal of the battery to the battery's -ve terminal) through any resistor without going through any other element, then that resistor is in a parallel circuit. Trace out the complete path current must take through R10. Does any of the current through R10 pass through any other resistor to reach the -ve terminal of the battery?

Another way of looking at it: could you remove from the circuit some resistors (i.e., use an eraser to erase them from your pencil drawing) without affecting the current through R10? If so, then R10 must be in its own parallel circuit.

 

[november1992]

Thanks! I got it.

 

[NascentOxygen]

A different approach would be to take a red marking pen, and from the + terminal of the battery colour the wires red right up to each element. Every point on that red line is at the same voltage as the + terminal of the battery. Similarly, use a blue pen for wires from the - terminal.

You can then see how every resistor has one of its ends sitting at the battery's + voltage, and the other end at the - voltage. So, having shown that the battery voltage is being applied directly across each resistor, you can calculate their individual currents.

 

[DeeNos]

I would suggest breaking down the problem into smaller parts and using Ohm's Law (V=IR) to solve for the currents in each resistor. First, determine if the circuit is in series or parallel. In this case, it appears to be a parallel circuit. Then, use the formula I=V/R to calculate the current in each resistor. Remember to use the voltage drop across each resistor, which can be found by using Kirchhoff's Voltage Law (KVL). Additionally, make sure to pay attention to the direction of the current flow and use the appropriate signs in your calculations. If you are still having trouble, I would suggest consulting with a classmate or your instructor for further assistance.