Balance a Wheatstone bridge
"Balance a Wheatstone bridge" is a free, interactive Class 12 Physics simulation for NEET and JEE, built on the lesson "Wheatstone bridge" in Current Electricity. A cell drives current from A to C through two paths. The galvanometer G joins B and D. Press Show the current and watch the red dots in the middle arm: they flow whenever B and D are at different potentials. At balance P/Q = R/S, so B and D are at the same potential. The middle arm then carries no current, whatever its resistance and whatever the battery. Check P/Q = R/S before you drop the middle resistor from a network. JEE Main asked 65 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
From the lesson Wheatstone bridge in Current Electricity. Change the values and watch what happens.
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 § "Wheatstone Bridge"
- Four resistors form a closed loop; a battery is connected across one pair of opposite corners and a galvanometer across the other pair.
- The bridge is balanced when no current flows through the galvanometer; the two ends of the galvanometer are then at the same potential.
- Balance condition, using our own labels: the battery is across corners A and C; path A→B→C has P (from A to B) then Q (B to C), and path A→D→C has R (A to D) then S (D to C); the galvanometer joins B and D. The bridge is balanced when P/Q = R/S, which is the same as PS = QR (products of opposite arms equal).
- Whatever letters a figure uses, check the condition this way: take the two resistors meeting at one battery corner; each one's ratio to the resistor that follows it on its own path must be the same for both paths.
- At balance, the galvanometer branch (or any resistor put in its place) can be removed, and the network reduces to two parallel series-pairs.
- The balance condition does not depend on the emf of the battery or the resistance of the galvanometer.
- If the ratios are not equal, the bridge is unbalanced and the middle resistor carries current; then Kirchhoff's rules must be used.
- The bridge lets an unknown resistance be found from three known ones by adjusting one of them until the galvanometer shows no deflection.
Questions
3 answers
- What does the "Balance a Wheatstone bridge" simulation show?
- A cell drives current from A to C through two paths. The galvanometer G joins B and D. Press Show the current and watch the red dots in the middle arm: they flow whenever B and D are at different potentials.
- 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 "Wheatstone bridge" in Current Electricity (Class 12 Physics).
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