Moving Coil Galvanometer
Galvanometer:
Galvanometer is a device which is used to detect the current or to measure small amount of current.
Working of Principal of Moving Coil Galvanometer
When a current carrying coil coil is placed in a region of magnetic field a restoring torque acting on it.
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Let us consider a coil area of cross section A and total number of turns N torque acting on a current carrying loop placed in region of magnetic field.
When current flows in wire a torque acting on it which produce a restoring torque in spring.
To remove sin from expression we use radical field, due to this the angle between magnetic field and magnetic moment becomes 90°, sin function get remove.
Radical field can be produce by the following.
- Use of cylinderical magnets.
- Use of soft iron core (it attracts the magnetic field around it ).
Current Sensitivity
Current Sensitivity is the ratio of current deflection per unit current.
For increase current sensitivity:
- increase in no of turns (N).
- Increase in area of cross section (A).
- Increase in magnetic field (B).
- Decrease in torsional constant (c).
Voltage Sensitivity
Voltage sensitivity is the ratio of deflection per unit voltage.
For increase voltage sensitivity:
- Increase in number of turns (N).
- Increase in area of cross section (A).
- Increase in magnetic field (B).
- Decreasing torsional constant (C).
- Decrease in resistance (R).
Note: Keeping the wires same if the current sensitivity is increase or decrease it can be done only in two manner by changing area of each tern both these factors are changed in same proportion due to which the voltage is sensitivity remains same.