What is Tangent Galvanometer? Explain briefly.
 
What are the possible conceptual questions from the chapter Magnetism & Matter?

Asked by debjyotisaha98 | 22nd Aug, 2015, 12:11: PM

Expert Answer:

Tangent galvanometer is an instrument for measuring small electric currents. With it one can measure the horizontal component of Earth's magnetic field also. It consists of a coil of insulated copper wire wound on a circular non-magnetic frame. Its working is based on the principle of the tangent law of magnetism B = Bh tanθ.
When a current is passed through the circular coil, a magnetic field (B) is produced at the centre of the coil in a direction perpendicular to the plane of the coil. The TG is arranged in such a way that the horizontal component of Earth’s magnetic field (Bh) is in the direction of the plane of the coil.
The magnetic needle is then under the action of two mutually perpendicular fields. If θ is the deflection of the needle, then according to tangent law, we get
 
begin mathsize 14px style straight B equals straight B subscript straight h tanθ space space space space space space space space space space space space space space space space space space space space space space space space...... space left parenthesis 1 right parenthesis If space the space current space passing space through space the space coil space of space radius space straight r space with space straight n space turns space is space straight I comma space then space the space field space generated space in space the space coil space is straight B equals fraction numerator straight mu subscript 0 nI over denominator 2 straight r end fraction space space space space space space space space space space space space space space space space space space space space space space space space space space...... space left parenthesis 2 right parenthesis Hence comma space we space get straight B subscript straight h tanθ equals fraction numerator straight mu subscript 0 nI over denominator 2 straight r end fraction therefore straight B subscript straight h equals fraction numerator straight mu subscript 0 nI over denominator 2 straight r tanθ end fraction equals fraction numerator straight mu subscript 0 straight n over denominator 2 straight r end fraction straight I over tanθ Now comma space the space term space straight I over tanθ equals straight K comma space is space known space as space the space reduction space factor space of space the space galvanometer space and space is space straight a space constant space for space any space galvanometer. Hence comma space we space have straight B subscript straight h equals fraction numerator straight mu subscript 0 nK over denominator 2 straight r end fraction end style
This is how, one can measure the horizontal component of Earth's magnetic field.
 
NOTE: Kindly post the other question as a separate query.

Answered by Romal Bhansali | 22nd Aug, 2015, 08:15: PM