Home / Topics / Current Electricity & Circuits
Meter bridge
Intermediate
Practical Wheatstone bridge using a wire.
A practical Wheatstone bridge using a 1 m wire and a sliding contact; the balance length ratio gives the resistance ratio: X = R(100 − l)/l.
R = 5 Ω, l = 40 cm: X = 7.5 Ω.
Use the middle of the wire for accuracy.
In more detail
A meter bridge is a practical form of the Wheatstone bridge, using a uniform wire and a sliding contact to find the balance point. The ratio of lengths gives the ratio of resistances.
Real-world uses
- School labs use meter bridges to measure unknown resistances.
- It teaches the principle of balancing circuits.
- Students use a meter bridge to measure an unknown resistance by sliding a contact along a uniform wire.
Open the interactive lesson, with simulation and quiz →
Frequently asked questions
How is the unknown found?
Measure the lengths on each side of the sliding contact at balance and use their ratio.
What makes it accurate?
A uniform wire and good contacts keep errors small.
Why is a uniform wire used?
Its resistance is proportional to length, so the position of the balance point gives the ratio of resistances directly.
Related topics in Current Electricity & Circuits
Kirchhoff's current law · Kirchhoff's voltage law · Wheatstone bridge · Potentiometer · Ammeter and voltmeter · Galvanometer