METER BRIDGE (Class 12 Physics – Notes)

METER BRIDGE (Class 12 Physics – Notes)

Definition:
A meter bridge is an instrument used to find an unknown resistance using the principle of Wheatstone bridge.

Principle:
When the bridge is balanced (no current flows through galvanometer):

R / X = l / (100 − l)

Where:
R = known resistance
X = unknown resistance
l = balancing length (in cm)

Formula:
X = R × (100 − l) / l

Construction:
• A uniform wire of 1 meter length
• Scale from 0 to 100 cm
• Two gaps for resistances (R and X)
• Galvanometer
• Jockey (sliding contact)

Working:

Connect known resistance (R) and unknown resistance (X).

Pass current through the circuit.

Slide the jockey on the wire.

Find the null point (galvanometer shows zero).

Measure length l from one end.

Use formula to calculate X.

Precautions:
• Wire should be uniform
• Balance point should be between 30 cm and 70 cm
• Connections must be tight
• Do not press jockey too hard

Uses:
• To find unknown resistance
• To compare resistances
• To verify laws of resistors

Видео METER BRIDGE (Class 12 Physics – Notes) канала Physics (11th and 12th) by Er GK Singh