i dont know anything about it ,
please... along with definition ,add some more points that can add up my marks..

Asked by preethambasilmartis | 21st Jun, 2016, 04:26: PM

Expert Answer:

In order to understand working mechanism of Tangent Galvanometer, the knowledge of Tangent law of Magnetism is essential.
Tangent law of Magnetism :-
  • The tangent law of magnetism states that the tangent of the angle of a compass needle which is due to the movement under the influence of magnetic field is directly proportional to the ratio of strengths of two perpendicular magnetic fields.
  • In simpler words, the tangent of the angle made by the moving needle under the magnetic field directly indicates the strength of the perpendicular magnetic fields. 
Tangent Galvanometer:-
  • Tangent galvanometer is the device which was used to measure small amounts of electric current. 
  • The working of tangent galvanometer is based on the principle of tangent law of magnetism.
  • It consists of a coil of insulated copper wire wound on a circular non-magnetic frame.
  • It is utmost necessary that the coil wound is done in helical arrangement otherwise, the field due to the wire will affect the compass needle, thus inducing an error in the reading.  
  • This frame is mounted vertically on a horizontal base for support.
  • The coil of insulated copper wire is usually rotated on a vertical axis passing through its centre.
  • A small sized magnetic compass with a  powerful magnetic needle is made to pivote at the centre of this coil, such that it is free to rotate in a horizontal plane.
  • The circular scale is used to read the movement of this magnetic needle which is divided into four quadrants, each ranging from 0° to 90°.
  • A pointer is attached to this needle at right angles, usually made up of thin alluminium as alluminium is lighter in mass.
  • The usual way of discarding possibilities of parallax is also used i.e placing of a plane mirror below the compass needle.  
  • The instrument needle starts moving firstly under the influence of Earth's magnetic field.
  • Movement continues untill the magnetic field of earth is parallel with the plane of coil.
  • Then, on application of an uknown current, a second magnetic field on the axis of the coil which is perpendicular to the Earth's magnetic field is created. 
  • Hence the compass needle responds to the vector sum of the two fields. 
  • This deflection angle is equal to the tangent of the ratio of those two fields.

Answered by Abhijeet Mishra | 29th Nov, 2017, 03:25: PM