Electricity · Physics

Meter Bridge Simulation

The Class 12 practical: slide the jockey along a 100 cm wire until the galvanometer reads zero, then find the unknown resistance from X = R(100 − l)/l. Record readings, swap R and X, and work out the wire's resistivity.

Interactive virtual lab · no download · works on phones and laptops

Chapter: Current Electricity
For: Class 12 practical · JEE
Time: ~15 min

How to use it

1Close the key, pick a value in the resistance box and choose an unknown coil.
2Drag the jockey along the wire until the galvanometer needle stays at zero.
3Press Record to add the reading to the table; repeat with other values of R.
4Swap R and X for the second set, then reveal the true value to check your average.

What to notice

At the balance point no current flows through the galvanometer: R/X = l/(100 − l).
The balance point is most accurate near the middle of the wire, so choose R close to X.
End resistance shifts the balance; swapping R and X and averaging cancels it.
The cell's EMF and the rheostat change the sensitivity, not the balance point.

For teachers

Teach it in 23 minutes

A lesson plan, questions to put to the class, a quick quiz you can project or print, and the formulas behind Meter Bridge.

1Hook
~2 min
- Ask: “The galvanometer reads zero. Does that mean no current is flowing anywhere in the circuit?” Then find a balance point.
2Demonstrate
~9 min
- Close the key, pick a value in the resistance box and choose an unknown coil.
- Drag the jockey along the wire until the galvanometer needle stays at zero.
- Press Record to add the reading to the table; repeat with other values of R.
- Swap R and X for the second set, then reveal the true value to check your average.
3Pause and ask
~5 min
- Have a student say this in their own words: At the balance point no current flows through the galvanometer: R/X = l/(100 − l).
- Have a student say this in their own words: The balance point is most accurate near the middle of the wire, so choose R close to X.
- Have a student say this in their own words: End resistance shifts the balance; swapping R and X and averaging cancels it.
- Have a student say this in their own words: The cell's EMF and the rheostat change the sensitivity, not the balance point.
4Check
~7 min
- Run the 7-question quiz below: project it and take answers by show of fingers (1–4), or print it as a worksheet.

About the Meter Bridge simulation

A metre bridge is a Wheatstone bridge built from a uniform 1 m wire. A known resistance R and an unknown X sit in two gaps; a jockey slides along the wire until a galvanometer between them reads zero. At that null point the bridge is balanced, so R/X equals the ratio of the two lengths of wire, l/(100 − l), and X can be found without knowing the current or the wire's resistance.

This meter bridge simulation is the Class 12 practical on screen: close the key, choose a value in the resistance box, slide the jockey until the galvanometer needle stops at zero, and record readings in an observation table. Swap R and X to cancel end error, change the rheostat to see how sensitivity changes, and work out the resistivity of the coil's wire. It covers Current Electricity (Class 12) and the metre bridge questions in JEE.

Also covers: metre bridge, meter bridge experiment, Wheatstone bridge, balance point, null point, unknown resistance, jockey, galvanometer, resistivity, rheostat, end correction.