Ans.
Principle : Galvanometer works on the principle of conversion of electrical energy into mechanical energy. When a current flows in a magnetic field it experiences a magnetic torque.
Working: Let the coil PQRS is suspended freely in the Magnetic Field.
Let l = length of the coil (PQ = RS )
b = breadth of the coil (PS = QR )
n = number of turns in coil
Area of each turn of coil , A =\( l \times b\)
Let B is the strength of magnetic field in which coil is suspended.
I is the current passing through the coil in the direction of PQRS.
let at any instant of time \(\alpha \) be the angle which the normal drawn on the plane of the coil makes with the direction of magnetic field. the rectangular current carrying coil will experiences a torque when placed in magnetic field is given by
\(\tau = NIBA \space Sin \space \alpha \)
Due to this defelecting torque, the coil rotates and the suspended wire gets twisted.
A restoring torque is set up in suspension wire.
Let \(\theta \) be the twist produced in the phosphor Bronze strip due to rotation of the coil
and k be the restoring torque per unit twist of the phosphor Bronze strip.
Then
total restoring torque produced = \(k\theta \)
in Equilibrium position of the coil,
Deflecting Torque = Restoring Torque
\(NIBA = k\theta \)
=> \(I= {k\theta \over NBA } = G\theta \)
Where \(G ={ k\over NBA } \space \space \space \space \space [Constant\space of \space Galvanometer]\)
It is known as Galvanometer Constant.
The Uniform Radial Magnetic Field keeps the plane of coil always parallel to direction of the magnetic field.
The soft iron core attracts the magnetic lines of force and hence the strength of the magnetic field increases if we use soft iron core. Thus the sensitivity of galvanometer increases.
Test
Naveen Sharma 8 years, 9 months ago
Ans.
Principle : Galvanometer works on the principle of conversion of electrical energy into mechanical energy. When a current flows in a magnetic field it experiences a magnetic torque.
Working: Let the coil PQRS is suspended freely in the Magnetic Field.
Let l = length of the coil (PQ = RS )
b = breadth of the coil (PS = QR )
n = number of turns in coil
Area of each turn of coil , A =\( l \times b\)
Let B is the strength of magnetic field in which coil is suspended.
I is the current passing through the coil in the direction of PQRS.
let at any instant of time \(\alpha \) be the angle which the normal drawn on the plane of the coil makes with the direction of magnetic field. the rectangular current carrying coil will experiences a torque when placed in magnetic field is given by
\(\tau = NIBA \space Sin \space \alpha \)
Due to this defelecting torque, the coil rotates and the suspended wire gets twisted.
A restoring torque is set up in suspension wire.
Let \(\theta \) be the twist produced in the phosphor Bronze strip due to rotation of the coil
and k be the restoring torque per unit twist of the phosphor Bronze strip.
Then
total restoring torque produced = \(k\theta \)
in Equilibrium position of the coil,
Deflecting Torque = Restoring Torque
\(NIBA = k\theta \)
=> \(I= {k\theta \over NBA } = G\theta \)
Where \(G ={ k\over NBA } \space \space \space \space \space [Constant\space of \space Galvanometer]\)
It is known as Galvanometer Constant.
The Uniform Radial Magnetic Field keeps the plane of coil always parallel to direction of the magnetic field.
The soft iron core attracts the magnetic lines of force and hence the strength of the magnetic field increases if we use soft iron core. Thus the sensitivity of galvanometer increases.
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