Question

An ammeter $A$ of finite resistance, and a resistor $R$ re joined in series to an idea; cell $C$. A potentiometer $P$ is joined in parallel to $R$. The ammeter reading is $I_0$ and the potentiometer reading is $V_0$. $P$ is now replaced by a voltmeter of finite resistance. The ammeter reading now is $I$ and the voltmeter reading is $V$.

• A. $I>I_0,V<V_0$
• B. $I>I_0,V=V_0$
• C. $I=I_0,V<V_0$
• D. $I<I_0,V=V_0$

Answer 1

The correct option is A $I>I_0,V<V_0$

After connecting voltmeter the equivalent resistance of the circuit decreases. Thus the current in the circuit increases . So $I>I_0$

Now the potential drop across ammeter $+$Potential drop across R $=$ EMF of cell .
As current increasing through ammeter, the potential drop across ammeter increases. Hence potential drop across R decreases. So, $V<V_0$