Question

While doing ohm’s law experiment a student observed that the pointer of the voltmeter coincides with the 15th division. If the least count of the voltmeter is 0.05 V, what is the observed reading?

• A. 0.75 V
• B. 0.075 V
• C. 7.5 V
• D. 75 V

Answer 1

The correct option is A

0.75 V

Least count

1. The value of one lowest division present in any measuring equipment is known as the least count.
2. If the least count of any instrument is $x$, it is self-evident and the pointer is now at the $n^{th}$ division. The value of the nth division will then be $n*(leastcount)$. Because the value of one division is the least count.

Step1: Given data

The least count of the voltmeter $=0.05volts$

The pointer of the voltmeter coincides with the ${15}^{th}$ division. So, $n=15$

Step2: Calculating observed reading

As a result, the observed reading will be the 15th division reading, which will be$(leastcount)*n=0.05*15=0.75volts$.

As a result, the voltmeter's observed value will be 0.75 volts.

Hence, option A is the correct answer.