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.
The assertion states that a galvanometer's deflection is directly proportional to the current flowing through it. This is accurate. Galvanometers operate on the principle of a current-carrying coil experiencing torque when placed in a magnetic field. The deflection angle θ is represented by the equation θ = kI, where I signifies the current and k is the proportionality constant, confirming the direct relationship between deflection and current.
The provided reason posits that the galvanometer's coil is suspended within a uniform radial magnetic field. This statement is also true. In a galvanometer, the coil is positioned between the poles of a magnet configured to produce a uniform radial magnetic field. This design ensures that the torque is proportional to the current across all coil positions.
Nevertheless, the stated reason does not accurately explain the assertion concerning the proportionality of deflection to current. While the uniform radial magnetic field arrangement facilitates consistent torque at varying coil positions, it is fundamentally the electromagnetic torque, arising from the interaction between the magnetic field and the current, that dictates the proportionality of the deflection.
Consequently, the appropriate conclusion is: Both Assertion (A) and Reason (R) are valid, but Reason (R) does not correctly elucidate Assertion (A).