# The measurement of an unknown resistance R

Question:

The measurement of an unknown resistance R is to be carried out using Wheatstone bridge. Two students perform an experiment in two ways. The first student take R2 = 10Ω and R1 = 5Ω. The other student takes R2 = 1000 Ω and R1 = 500 Ω. In the standard arm, both take R3 = 5 Ω. Both find R = R2/R1 R3 = 10 Ω within errors.

(a) the errors of measurement of the two students are the same

(b) errors of measurement do depend on the accuracy with which R2 and R1 can be measured

(c) if the student uses large values of R2 and R1, the currents through the arms will be feeble. This will make determination of null point accurately more difficult

(d) Wheatstone bridge is a very accurate instrument and has no errors of measurement

Solution:

(b) errors of measurement do depend on the accuracy with which R2 and R1 can be measured

(c) if the student uses large values of R2 and R1, the currents through the arms will be feeble. This will make determination of null point accurately more difficult