Question

In the metre bridge experiment of resistances, the known and unknown resistances are inter-changed. The error so removed is:

• A. end correction
• B. index error
• C. due to temperature effect
• D. random error

Answer 1

Answer: (A)

end correction

$\alpha ,\beta$ are the end correction on left and right side.

case 1:- Without interchanging.

$\frac{P}{Q}=\frac{R}{S}=\frac{X+\alpha +l_{1}P}{(Y+\beta +(100-l_1\left)P\right)}$ ..........( 1 )

case 2:- After interchanging.

$\frac{P}{Q}=\frac{R}{S}=\frac{Y+\propto +l_{2}P}{X+\beta +(100-l_2)P}$ ............( 2 )
on simplification of eq. (1) and (2) we get
$X=Y+(l_2-l_1)P$
$\therefore$ By interchanging the end correction is removed.