# A voltmeter of re

Concepts/Formula used:
Resistors in Series:

Resistors in parallel:

Ohm’s Law:

Potential Difference (V) across a resistor of resistance R when current I passes through it is given by Ohm’s law:

(a)

The given circuit is:

We can easily see that the voltmeter and R1 are in parallel. The equivalent resistance, r’ is given by:

We can redraw the circuit as follows:

Note that r’ and R2 are in series. The equivalent resistance is given by:

The current coming out of the battery also passes through r’. By Ohm’s law,

Now, the voltmeter reads the potential different across R1 .

(b)

The given circuit is now:

The equivalent resistance is :

The current is the same throughout the circuit as all components are in series and is given by:

Now, the potential difference across R1 is given by:

Hence, the potential difference across the 100Ω resistor before connecting the voltmeter was 28V.

Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation
view all courses
RELATED QUESTIONS :

<span lang="EN-USPhysics - Exemplar

<span lang="EN-USPhysics - Exemplar

Let there be n rePhysics - Exemplar

<span lang="EN-USPhysics - Exemplar

<span lang="EN-USPhysics - Exemplar

Two cells of emf Physics - Exemplar

<span lang="EN-USPhysics - Exemplar

<span lang="EN-USPhysics - Exemplar

Kirchhoff ’s juncPhysics - Exemplar