Question

In the experiment of calibration of a voltmeter, a $1.1V$ standard cell gets balanced at $440cm$ length of wire. The balancing length corresponding to a potential difference between the ends of a resistance comes out to be $190cm$. A voltmeter shows $0.5V$ for this potential difference. The error in the reading of voltmeter will be:

• A. $0.025V$
• B. $25V$
• C. $2.5V$
• D. $0.25V$

Answer 1

The correct option is A $0.025V$

It is given that,

Length of wire is, $l=440cm$

Voltage of voltmeter is,$1.1V$

Balancing length, $l^{\prime }=190cm$

At balancing length potential difference, $V^{\prime }=0.5V$

Potential per unit length, $=\frac{1.1}{440}=0.0025V/cm$

At balancing length, voltage reading is $=0.0025\times 190=0.475V$

So, error is $0.5-0.475=0.025V$