Solving Simple Circuits: Analyzing Currents Using Ohm's Law and Kirchoff's Laws

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TheTopGun
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Homework Statement


Hello! I'm having difficulty analyzing https://dl.dropboxusercontent.com/u/53341615/Circuit%20Diagram.png circuit and determining the currents I1,I2,I3.

Homework Equations


Ohm's Law
Kirchoffs Laws
Current and Volatage divider

The Attempt at a Solution


So far all I can manage is https://dl.dropboxusercontent.com/u/53341615/IMG_20130827_211859.jpg the circuit, I am sure I am suppose to use current or voltage divider I just can't work out where.

Using software simulation the values should be around ...I1=0.5404, I2=0.8109, I3= -0.2702mA

Any help on which rules and where to apply them would be much appreciated!

~thanks
 
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TheTopGun said:

Homework Statement


Hello! I'm having difficulty analyzing https://dl.dropboxusercontent.com/u/53341615/Circuit%20Diagram.png circuit and determining the currents I1,I2,I3.

Homework Equations


Ohm's Law
Kirchoffs Laws
Current and Volatage divider

The Attempt at a Solution


So far all I can manage is https://dl.dropboxusercontent.com/u/53341615/IMG_20130827_211859.jpg the circuit, I am sure I am suppose to use current or voltage divider I just can't work out where.

Using software simulation the values should be around ...I1=0.5404, I2=0.8109, I3= -0.2702mA

Any help on which rules and where to apply them would be much appreciated!

~thanks

Your simplified circuit is correct except you have a typo for the left resistor. Should be kOhms, not Ohms.

In problems like this, I prefer to write the KCL equations, and just solve them simultaneously. That's the most intuitive technique for me, and almost always works without modification.

So this is a pretty simple circuit -- call the voltage at the top node V1, and write the one KCL equation for that node. You can then solve for that voltage, which let's you solve for the 3 currents that the problem is asking for. In problems with multiple nodes, just write the KCL equations for each node and solve the equations simultaneously.

I prefer to write the KCL equation(s) as the sum of all the currents out of each node equal zero.

Can you show us your work given those hints?
 
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berkeman said:
Your simplified circuit is correct except you have a typo for the left resistor. Should be kOhms, not Ohms.

In problems like this, I prefer to write the KCL equations, and just solve them simultaneously. That's the most intuitive technique for me, and almost always works without modification.

Ahh thankyou very much. I was messing around with equations I didn't need. I just wrote out the Ohms, KCL & KVL equations then solved simultaneously, came out perfect.

Once again, thanks :)