What is torsional constant of the spring used in a galvanometer?

Explanation

To find the torsional constant of the spring used in a galvanometer, we need to understand the relationship between the torque acting on the loop in the magnetic field and the torsional constant of the spring. Here’s a step-by-step solution:

### Step 1: Understanding Torque in a Magnetic Field
When a current-carrying loop is placed in a magnetic field, it experiences a torque. The torque (\( \tau \)) on the loop can be expressed using the formula:
\[ \tau = \mathbf{m} \times \mathbf{B} \]
where \( \mathbf{m} \) is the magnetic moment of the loop, and \( \mathbf{B} \) is the magnetic field.
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