Q. In the diagram shown, the reading of voltmeter is $20\ V$ and that of ammeter is $4\ A.$ The value of $R$ should be (Consider given ammeter and voltmeter are not ideal)
A) Equal to $5\ \Omega$
B) Greater than $5\ \Omega$
C) Less than $5\ \Omega$
D) Greater or less than $5\ \Omega$ depending on the material of $R$
Explanation
(c) If resistance of ammeter is $r$ then
$20 = (R + r)4 \Rightarrow R + r = 5 \Rightarrow R < 5\Omega$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.