Walking round a loop with Kirchhoff
"Walking round a loop with Kirchhoff" is a free, interactive Class 12 Physics simulation for NEET and JEE, built on the NCERT section "Kirchhoff's rules" in Current Electricity. A two-loop network with two cells: walking round a chosen loop plots the potential step by step (+ε, −IR …) and the steps must sum to zero. NEET has asked about this idea 2 times in 10 years of papers. JEE Main asked 65 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
From the lesson Kirchhoff's rules in Current Electricity. Change the values and watch what happens.
What it shows
NCERT § Kirchhoff's Rules
A two-loop network with two cells: walking round a chosen loop plots the potential step by step (+ε, −IR …) and the steps must sum to zero.
Controls
5 to try
- Sliderε1 0–12 V
- Sliderε2 0–12 V
- SliderR1, R2, R3 1–20 Ω
- Toggleassumed direction of each branch current
- Segmentedloop left / right / outer
Try this
Set ε2 so the middle branch carries zero current; then flip an assumed direction and see the solved current turn negative with the same size.
Common mistake
Mixing up sign rules for cells and resistors in loop equations.
In NEET
10 years of papers
Asked 2 times in 10 years of NEET.
See the past questions: Kirchhoff's Rules, Current Electricity (chapter)
In JEE Main
42 shifts analysed
65 questions from Current Electricity across the 42 JEE Main shifts Lumi has analysed (2017–2026).
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.
Questions
5 answers
- What does the "Walking round a loop with Kirchhoff" simulation show?
- A two-loop network with two cells: walking round a chosen loop plots the potential step by step (+ε, −IR …) and the steps must sum to zero.
- What mistake does the "Walking round a loop with Kirchhoff" simulation fix?
- A common mistake it clears up: mixing up sign rules for cells and resistors in loop equations.
- Has NEET asked about this idea?
- Yes. NEET has asked about this idea 2 times in 10 years of papers.
- Does JEE Main ask questions from Current Electricity?
- Yes. JEE Main asked 65 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
- Is this simulation free?
- Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "Kirchhoff's rules" in Current Electricity (Class 12 Physics).
Embed this simulation
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