An ammeter and a voltmeter of resistance R ar | vedclass

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(D) Let the electromotive force of the cell be $E$. The total resistance of the circuit initially is $R_{total} = R_A + R_V = R + R = 2R$, where $R_A$

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$A$ will increase and $V$ will decrease

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(D) Let the electromotive force of the cell be $E$. The total resistance of the circuit initially is $R_{total} = R_A + R_V = R + R = 2R$, where $R_A$ is the resistance of the ammeter and $R_V$ is the resistance of the voltmeter.Initially, the current $A = E / 2R$ and the voltage $V = A 	imes R = E/2$.When another resistance $R$ is connected in parallel with the voltmeter, the new equivalent resistance of the parallel combination is $R' = (R 	imes R) / (R + R) = R/2$.The new total resistance of the circuit becomes $R_{new} = R_A + R' = R + R/2 = 3R/2$.Since $R_{new}  1/2$, the reading $A$ increases.The new voltage across the voltmeter is $V' = A' 	imes R' = (2E / 3R) 	imes (R/2) = E/3$. Since $E/3 Therefore, $A$ will increase and $V$ will decrease.

An ammeter and a voltmeter of resistance $R$ are connected in series to an electric cell of negligible internal resistance. Their readings are $A$ and $V$ respectively. If another resistance $R$ is connected in parallel with the voltmeter, what happens to the readings $A$ and $V$?

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