The measurement of an unknown resistance R is to be carried out using Wheat stones bridge (see Fig. 3.25 of NCERT Book). Two students perform an experiment in two ways. The first students take R 2 = 10 Ω and R 1 = 5 Ω. The other student takes R 2 = 1000 Ω and R 1 = 500 Ω. In the standard arm, both take R 3 = 5 Ω. Both find within errors.

Question

Philoid · Accepted Answer

A Wheatstone bridge is an arrangement of four resistances, which under a balanced condition can help us find out a resistance, if the other three are given.

For a balanced Wheatstone bridge,

Substituting the values of R₂, R₁ and R₃ for student 1 we get R_X as 10Ω.

Doing the same for student 2 we again get R_X=10Ω.

The errors in the calculation depends on the sensitivity of the bridge which depends on the resistances involved. If R₂ and R₃ are very large, the current from these arms would be proportionately small and thus will make it difficult to locate a null point.

As different setups of Wheatstone bridge are used (with different resistances) errors in both cases will differ.

1280px-Wheatstonebridge.svg.png

Hence, option (b) and (c) are correct.