Question

Assertion :The sensitivity of a moving coil galvanometer is increased by placing a suitable magnetic material as a core inside the coil. Reason: Soft iron has a high magnetic permeability and cannot be easily magnetized or demagnetized.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is C Assertion is correct but Reason is incorrect

$c\varphi =BINA$

$\varphi =\left(\frac{BNA}{c}\right)I$

Using iron core, value of magnetic field increases. So, deflection increases for the same current. Hence, sensitivity increases.
Soft iron can be easily magnetized or demagnetized.