Exam Question

### (a) Measurement of Large Current using a Moving Coil Ammeter
A standard moving coil instrument, such as a Permanent Magnet Moving Coil (PMMC) galvanometer, is an extremely sensitive device designed to measure very small currents, typically in the milliampere (mA) range. The coil is wound with very fine copper wire which has a limited current-carrying capacity. Passing a large current directly through this coil would generate excessive heat ($$P = I^2R$$), leading to the coil burning out and permanent damage to the instrument.
To adapt such an instrument for measuring large currents, a **shunt resistor** is employed. The principle is to bypass the majority of the current around the sensitive meter movement.
**Method and Construction:**