Steps for applying Kirchhoff rules
1. Draw the circuit; label all the known and unknown quantities.
2. Assign a direction to the currents in each part of the circuit:
- If you guess the direction of the current incorrectly, your result will be negative. However, the magnitude will be correct.
- You must adhere to the assigned direction.
3. Apply the junction rule to any junction in the circuit.
4. Apply the second rule to as many loops in the circuit as needed:
- Choose a direction (clockwise or counter-clockwise).
- If a resistor is traversed in the direction of the current: the change in potential is – I R.
- If a resistor is traversed opposite to the direction of the current: the change in potential is + I R.
- If an emf is traversed from the + to the – terminal: The change in potential is - .
- If an emf is traversed from the - to the + terminal: The change in potential is + .
5. Solve the equations simultaneously for the unknown quantities.