I am having a little trouble remembering the sign convention for a voltage source in series with a resistor. Lets say that the voltage source is on the left hand side of a circuit with its negative terminal on the bottom and positive terminal on the top and the resistor is in series with the positive terminal.

If I am looking for the current through this resistor, will it be positive or negative? Or does it really depend on my the reference polarity that I assign to the resistor.


1 Answer 1


It's a common beginner's trap, you worry too much about this ! Just pick a sign / direction that seems to make sense to you, if you have no preference or don't know, just choose any. It actually does not matter ! Because when you apply the KVL/KCL correctly and fill in the numbers, it will be positive when you have choosen correctly but negative when you have not. So worst case, you'll get a negative number meaning the (positive value) current flows in the opposite direction or the (positive value) voltage has + and - reversed.

The only thing you need to be beware of that once you choose a pos/neg or current flow direction is to stick with that choice.

Try it and you'll see it makes sense :-)


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