Question

In a voltmeter there are 20 divisions between the '0' mark and 0.5 V mark. Calculate its least count.

Answer 1

We are given the number of divisions, initial reading and final reading on a voltmeter. We know the equation to find the least count of a voltmeter. By finding the potential difference and substituting the known values in the equation to find least count, we get the solution.

Formula used:
Potential difference, Pd = final reading – initial reading
Least count of a voltmeter, $\text{LC=}\dfrac{\text{potential difference}}{\text{number of divisions}}$
Complete step by step answer:
We are given a voltmeter and it is said that there are 20 divisions between 0 V and 0.5 V on the voltmeter.
We know that the least count of voltmeter is the minimum potential difference that can be measured between the two given terminals.
In the given situation, the initial reading on the voltmeter = 0 V
And the final reading on the voltmeter = 0.5 V
We know that the potential difference is the difference between final reading and initial reading,
Potential difference = Final reading – Initial reading.
Potential difference = 0.5 V – 0 V = 0.5 V
We are also given the total number of divisions,
Number of divisions = 20 divisions
Therefore we can calculate the least count of the voltmeter.
$\text{LC=}\dfrac{\text{potential difference}}{\text{number of divisions}}$
By substituting the known values in the above equation, we get
$\Rightarrow LC=\dfrac{0.5}{20}$
$\Rightarrow LC=0.025V$
Hence least count of the given voltmeter is 0.025 V.

Note:
A voltmeter also known as voltage meter is an instrument which is used to measure the voltage or potential difference across two terminals in an electrical circuit.
Potential difference or voltage is simply the difference in potential between two points. It can also be defined as the total amount of work done to move a unit charge from one point to another.