Q. 485.0( 2 Votes )

# A voltmeter of re

Answer :

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 .  Hence, the voltmeter reads 24V.

(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.

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