Converting a Galvanometer into an Ammeter

To convert a galvanometer into an ammeter with a range of 0-5A, we need to add a shunt resistor to the galvanometer circuit. The shunt resistor will bypass most of the current, allowing only a fraction of it to pass through the galvanometer.

Calculating the Shunt Resistor Value:
To determine the value of the shunt resistor, we need to consider the desired full-scale deflection current and the resistance of the galvanometer coil.

Given:
- Resistance of the galvanometer coil (Rg) = 40 ohm
- Full-scale deflection current (Ig) = 5mA

Using Ohm's Law, we can calculate the resistance of the shunt resistor (Rs) that will allow the desired full-scale deflection current to pass through the galvanometer.

Ohm's Law: V = IR

Step 1:
Calculate the voltage drop across the galvanometer coil at full-scale deflection.
Vg = Ig * Rg
Vg = 5mA * 40 ohm
Vg = 0.2V

Step 2:
Determine the desired full-scale deflection current for the ammeter.
Im = 5A

Step 3:
Calculate the resistance of the shunt resistor required to allow the desired full-scale deflection current to pass through the galvanometer.
Rs = Vg / Im
Rs = 0.2V / 5A
Rs = 0.04 ohm

Adding the Shunt Resistor:
Once the value of the shunt resistor (Rs) is determined, it needs to be connected in parallel with the galvanometer. The shunt resistor will provide a low-resistance path for most of the current, allowing only a fraction of it to pass through the galvanometer coil.

Important Considerations:
- The shunt resistor should have a very low resistance compared to the galvanometer coil to ensure most of the current bypasses the galvanometer.
- The shunt resistor should be designed to handle the maximum current that may flow through the ammeter. In this case, it should be able to handle up to 5A.
- It is recommended to use precision resistors to ensure accurate current measurement.
- The shunt resistor should be connected in parallel with the galvanometer, ensuring proper polarity and connection.

Summary:
In summary, to convert a galvanometer into an ammeter with a range of 0-5A, a shunt resistor is added in parallel with the galvanometer. The value of the shunt resistor is calculated based on the desired full-scale deflection current and the resistance of the galvanometer coil. The shunt resistor provides a low-resistance path for most of the current, allowing only a fraction of it to pass through the galvanometer, thereby enabling accurate current measurement.