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In a metre bridge experiment, swapping the two resistances moves the balance point 10 cm to the left. If the two resistances add up to 1000 ohm in series, what was the value of the resistance originally placed in the left gap?

1. 505 ohm
2. 550 ohm
3. 910 ohm
4. 990 ohm

Correct answer: 550 ohm

Solution

Using the metre bridge balance condition before and after interchange with the constraint R+R'=1000 gives the original left resistance as 550 ohm.

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