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I have a circuit here https://www.circuitlab.com/circuit/75484k/wk3-1/

Very simple circuit.

I am using Circuit Lab to draw circuits given to me in problems, I then workout the solutions and then confirm values with Circuit Lab.

Now on this circuit I am using Kirchoffs laws to find the currents of I1, I2 and I3

Why is this circuit showing I1 as a negative value ?

it should be 3.0 A where I1 = I2 + I3

It clearly shows I2 and I3 being positive values which will not equate to a negative value.

My solution comes out with positive, using kirchoffs laws with this circuit comes out as 2 + 1 = 3 not -3 ?

Confused ?

Thanks

Circuit Lab is sensitive to which side of the component you click on when it comes to current, I think this picture will help clear this up.

mmm ok. Thank you very much for the response. But how would I know which side to use ?

You have indicated current flow on there, if this was a circuit with 2 DC supplies where Kirchoffs would come in more useful then you assume a current flow to work with the equations so getting negative and positive values along the way.

I am interested in why it will not work on the other side of the resistor ?

But I guess it is just circuit lab, so how would i know which value was correct ? aside from the I2 + I3 ?

Thanks

say you click on a junction between a wire and a component then it reports the current from the wire into the component. This mean that if you click on both sides of a component you should get equal and opposite currents. It can get crazy when you have 3 or more components at the same junction, but in that case you can just spread every thing out.

as for knowing which is correct I would say to make loops and probe when you reach a component, not after the component.

ok, Thanks very much for the help.

Cheers