Consider the scale of a voltmeter shown in the diagram and answer the following questions:

(a) What is the least count of the voltmeter?

(b) What is the reading shown by the voltmeter?

(c) If this voltmeter is connected across a resistor of 20Ω

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(a) Maximum value of voltmeter = 3.0 (given)

Total count of marking in the voltmeter= 20

Therefore, 

Least count of voltmeter = $\frac {3}{20}=0.15V$ 

(b) Reading shown by the voltmeter is-

$\Rightarrow 1.5+0.15+0.15$    $(\because each\ marking\ has\ the\ value\ 0.15)$

$\Rightarrow 1.8V$.

(c) Given:

Resistor, $R=20\Omega$

Reading of voltmeter, $V=1.8V$

To find: Current flowing through the resistor, $I$.

Solution:

By Ohm's law, we know that, 

$V=I\times R$

In terms of $I$ it is given as-

$I=\frac {V}{R}$

Putting the required values, we get-

$I=\frac {1.8}{20}$

$I=0.09A$

Thus, the current flowing through the resistor is 0.09A.

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Updated on: 10-Oct-2022

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