Simulation · Physics · Class 12
Walking round a loop with Kirchhoff
From the lesson Kirchhoff's rules in Current Electricity. Change the values and watch what happens.
Walking round a loop with KirchhoffPhysics · Class 12
The idea behind it
NCERT § "Kirchhoff's Rules"
- Junction rule: the total current flowing into any junction equals the total current flowing out of it. It follows from conservation of charge in steady state.
- Loop rule: going around any closed loop, the changes in potential add up algebraically to zero. It follows from the electrostatic force being conservative (energy conservation).
- Assign a current with an assumed direction to each branch; if the solution gives a negative value, the actual current flows the other way, and the magnitude is still correct.
- Going through a resistor in the direction of the assumed current, the potential falls by IR; going against it, it rises by IR.
- Going through a cell from its negative to positive terminal, the potential rises by ε; from positive to negative, it falls by ε.
- Use the junction rule first to reduce the number of unknown currents, then write as many independent loop equations as are needed.
- Symmetry in a network (equal potentials at symmetric points) can remove resistors that carry no current and simplify the work.