Q. An ammeter gives full scale deflection when a current of 2A flows through it. The resistance of ammeter is 12$\ \Omega$. If the same ammeter is to be used for measuring a maximum current of 5A, then ammeter must be connected with a resistance of
A) 18$\ \Omega$in parallel
B) 8$\ \Omega$in parallel
C) 18$\ \Omega\ in\ series$
D) 8$\ \Omega\ in\ series$
Explanation
(b) From the formula shunt resistance
$\ \ \ \ \ \ \ \ S = \frac{i_{g} \times g}{i - i_{g}}$
$\Longrightarrow \ \ S = \frac{2 \times 12}{5 - 2} = 8\Omega\ \ \ \ \ (in\ parallel)$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.