Exam Question

### (a) Measurement of Large Current by Moving Coil Ammeter (6 Marks)
A moving coil ammeter, specifically a Permanent Magnet Moving Coil (PMMC) instrument, is designed with a delicate coil that can only handle very small currents, typically in the milliampere (mA) range. To measure currents significantly larger than its full-scale deflection (FSD) current, a low-resistance conductor called a **shunt** is used.
**Principle of Operation:**
1. **Parallel Connection (Current Division):** The shunt resistor is connected in parallel with the meter's moving coil. When a large current enters the measurement circuit, it reaches a junction where it splits. The majority of the current bypasses the delicate meter coil and flows through the low-resistance path provided by the shunt. A small, proportional fraction of the total current flows through the meter coil.