First slide

Resistors

Question

The actual value of resistance ‘R’ , shown in the figure is $40 Ω$ . This is measured in an experiment as shown using the standard formula $R = \frac{V}{I}$ , where V and I are the readings of the voltmeter and ammeter respectively. If the measured value of R is 5 % less, then the internal resistance of the voltmeter is

Easy

A

$350 Ω$
B

$570 Ω$
C

$35 Ω$
D

$760 Ω$

Solution

Resistor and voltmeter are in parallel
$R_{e f f} = \frac{R R_{V}}{R + R_{V}} I t' s g i v e n t h a t R_{e f f} = 0.95 R [5 % l e s s t h a n R] \Rightarrow 0.95 R = \frac{R R_{V}}{R + R_{V}} \Rightarrow 0.95 (40) = \frac{(40) R_{V}}{(40) + R_{V}} \Rightarrow 38 = \frac{(40) R_{V}}{(40) + R_{V}} \Rightarrow R_{V} = 760 Ω$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App