Question

Assertion (A): The deflection in a galvanometer is directly proportional to the current passing through it. 

Reason (R): The coil of a galvanometer is suspended in a uniform radial magnetic field.

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A)
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false and Reason (R) is also false.

Hint:

The deflection in a galvanometer is directly related to the current, but the suspension of the coil in a uniform magnetic field is not the only reason for this relationship.

Answer 1

The Correct Option is B

The assertion given is that the deflection in a galvanometer is directly proportional to the current passing through it. This is indeed true. A galvanometer works on the principle that a current-carrying coil placed in a magnetic field experiences a torque. The deflection θ in the galvanometer is given by the equation θ = kI, where I is the current and k is a constant of proportionality, indicating that the deflection is directly proportional to the current. 

The reason provided is that the coil of a galvanometer is suspended in a uniform radial magnetic field. This is also true. In a galvanometer, the coil is placed between the poles of a magnet designed to create a uniform radial magnetic field, ensuring that the torque is proportional to the current for all positions of the coil.

However, the reason mentioned is not the correct explanation for the assertion regarding the proportionality of deflection to current. The arrangement of the uniform radial magnetic field allows for consistent torque at different coil positions, but it is primarily the electromagnetic torque resulting from the interaction of the magnetic field and current that causes the deflection proportionality.

Therefore, the correct option is: Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).