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Physics · Practical apparatus

Metre bridge combinations

Practical apparatus

Slide the jockey until detector voltage reaches zero. Repeat with one resistor and its series or parallel combination; do not infer resistance from an unbalanced position.

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Metre bridge combinations

மீட்டர் பிரிட்ஜில் கண்டறிவி பூஜ்யமாகும் வரை ஜாக்கியை நகர்த்தவும். தொடரும் பக்க இணைப்பும் விகிதத்தைக் மாற்றும்.

Key notes, relationships and model limits

Key relationship

X/R=ℓ/(100−ℓ) at null.

Practical tip

Slide the jockey until detector voltage reaches zero. Repeat with one resistor and its series or parallel combination; do not infer resistance from an unbalanced position.

Common trap

Use the bridge ratio only at a null. This panel determines resistance combinations, rather than completing a wire-resistivity measurement.

Model limits

uniform one-metre wire, no end/contact resistance, ideal null detector. Inferred resistance is valid only when detector reads zero.

What you will learn

Adjust metre bridge combinations apparatus, observe its reading and derive the indicated physical quantity.

Try the experiment

Try both scenarios, change one control, and predict the result before checking the graph and readouts.

Think of it this way

Change one input while keeping the others fixed, as you would in a controlled experiment.

Worked example

With X=10 Ω and R=20 Ω, balance is 100×10/(10+20)=33.33 cm.

Why this matters

The model connects metre bridge combinations with an observable reading. Check the equation and assumptions before applying it.

Before you start

SI units · algebra · graph reading

Check your understanding

For equal unknown and known resistances, balance mark is?

Read the explanation

50 cm.

Course connection: Virtual apparatus preparation. Check exact board/exam membership in the syllabus sources. Physical practical work remains necessary.