Exam Question

### Principle of Operation (4 Marks)
The operation of a Permanent-Magnet Moving-Coil (PMMC) galvanometer is based on the **Motor Principle** or **Lorentz Force**. The principle states that a current-carrying conductor placed within a magnetic field will experience a mechanical force. In the context of the galvanometer:
1. **Deflecting Torque ($$T_d$$):** When a direct current (DC) flows through the windings of the moving coil, the coil sides (which are perpendicular to the magnetic field) experience equal and opposite forces. These two forces form a couple, creating a turning moment or deflecting torque that causes the coil to rotate.
* The magnitude of this deflecting torque is directly proportional to the current flowing through the coil, the strength of the magnetic field, and the dimensions of the coil.