Meter Bridge and End Corrections
With gap resistances X and R and balance length l measured from X's end on a 100 cm ideal wire, X/R = l/(100-l). End corrections replace geometric lengths by their effective lengths.
Why this shows up in the exam
Unknown resistance measurement · Shift after series or shunt addition · Estimating uncertainty from least count
Learn the idea
A meter bridge converts a resistance ratio into a ratio of uniform-wire lengths. The slide wire is a continuous pair of Wheatstone arms. At the null point, resistance per unit length cancels if the wire is uniform.
🧠 Memory hook: The resistance beside the measured length belongs in the same ratio position.
Get this one clearly and it pays off every single time it shows up in the paper. 🎯
Formulas & facts to keep ready
- X/R = l/(100-l) — ideal meter bridge with l measured from X side
- X/R = (l+e₁)/(100-l+e₂) — one common end-correction model; follow stated convention
How to approach it
- 1Mark left and right gap resistances
- 2Write the balance ratio from the actual diagram
- 3Apply shifts or corrections before solving
Common slip-ups that cost marks
- •Reversing the length ratio
- •Ignoring which end l is measured from
- •Applying ideal lengths when end corrections are given
🌟 That's the whole idea — you've got this. Try the practice set below; every question you attempt makes it stick a little harder.
Original chapter practice
Original questions for this chapter, not past-paper questions or an exact mapping to this individual concept.
A cell of emf 6 V and internal resistance 1 ohm is connected to a 2 ohm resistor. Find the circuit current.
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