Question

Assertion : In the circuit shown in figure ammeter and voltmeter are non-ideal. Why positions of ammeter and voltmeter are changed, reading of ammeter will increase while of voltmeter will decrease.
Reason : Resistance of an ideal ammeter is zero while that of an ideal voltmeter is infinite.
A. If both Assertion and Reason are true and the Reason is correct explanation of the Assertion.
B. If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
C. If Assertion is true, but the Reason is false.
D. If Assertion is false but the Reason is true.

Answer 1

Correct Answer - B
Even if ammeter is non ideal its resistance should be small and net parallel resistance is less than the smallest individual resistance.
`:. R_("net")lt` resistance of ammeter in changed situation. Hence, net resistance of the circuit will decrease. So, main current will increase. But maximum percentage of main current will pass through ammeter (in parallel combination) as its resistance is less. Hence, reading of ammeter wil increase.
Initial voltmeter reading`= `emf of battery
Final voltmeter reading=emf of battery
-potential drop across shown resistancce.
Hence, voltmeter reading will decrease.