A galvanometer is a device used to measure small electrical currents. It works by using a coil of wire and a magnet to create a magnetic field. When an electrical current passes through the coil, it will experience a force due to the interaction between the magnetic field and the current. This force causes the coil to rotate, and the amount of rotation is proportional to the strength of the current.
To convert a galvanometer into an ammeter, a shunt resistor is added in parallel to the galvanometer. The shunt resistor allows most of the current to bypass the galvanometer, while only a small portion of the current passes through the coil. This allows the galvanometer to measure larger currents without being damaged.
The purpose of using a galvanometer as an ammeter is to accurately measure the magnitude of electrical currents. Galvanometers have a high sensitivity and can measure very small currents, making them useful in scientific experiments and electrical circuit analysis. By converting a galvanometer into an ammeter, it can be used to measure larger currents while still maintaining its accuracy.
One limitation of using a galvanometer as an ammeter is that it can only measure direct currents (DC). It cannot measure alternating currents (AC) due to the fact that the coil will constantly rotate in one direction. Additionally, galvanometers have a limited range of measurement and cannot measure extremely high currents without the risk of damaging the device.
To calibrate a galvanometer for use as an ammeter, a known current is passed through the device and the resulting deflection is measured. This deflection is then used to calculate the value of the shunt resistor needed to convert the galvanometer into an ammeter with the desired measurement range. The shunt resistor can be adjusted until the readings on the galvanometer match the known current values, ensuring accurate measurements.