what is a tangent galvanometer?

Answer 1

A tangent galvanometer is an instrument used for the measurement of current. It works on the basis of tangent law of magnetism.

Construction
A TG consists of a circular coil of insulated copper wire wound on a circular non magnetic frame. The frame is mounted vertically on a horizontal base provided with levelling screws on the base. The coil can be rotated on a vertical axis passing through its centre. A compass box is mounted horizontally at the centre of a circular scale. The compass box is circular in shape. It consists of a tiny, powerful magnetic needle pivoted at the centre of the coil. The magnetic needle is free to rotate in the horizontal plane. The circular scale is divided into four quadrants. Each quadrant is graduated from 0° to 90°. A long thin aluminium pointer is attached to the needle at its centre and at right angle to it. To avoid errors due to parallax a plane mirror is mounted below the compass needle.

The tangent galvanometer was first described in an 1837 paper by Claude-Servais-Mathias Pouillet (1790-1868), who later employed this sensitive form of galvanometer to verify Ohm's law. To use the galvanometer, it is first set up on a level surface and the coil aligned with the magnetic north-south direction. This means that the compass needle at the middle of the coil is parallel with the plane of the coil when it carries no current. The current to be measured is now sent through the coil, and produces a magnetic field, perpendicular to the plane of the coil, and directly proportional to the current. The magnitude of the magnetic field produced by the coil is B; the magnitude of the horizontal component the earth's magnetic field is B'. The compass needle aligns itself along the vector sum of B and B' after rotating through an angle Ø from its original orientation. The vector diagram shows that tan Ø = B/B'. Since the magnetic field of the earth is constant, and B depends directly on the current, the current is thus proportional to the tangent of the angle through which the needle has turned.

Answer 2

It is often measured using an instrument called a tangent galvanometer. Able to measure the presence as well as the direction and power of currents, the instrument was first used in the early 1800s. It typically has a vertical copper wire coil, wrapped around a circular frame, and a compass in the middle. The compass needle generally responds to the magnetic field of the electrical current, which is compared to the Earth’s magnetic field in the experiment. This scientific instrument has been built in many forms and more modern ones often use beams of light to determine measurements, while some versions are used to measure the magnetic field of the Earth

The instrument works based on the tangent law of magnetism. This principle defines the tangent of the angle, traveled through by the compass needle, as being proportionate to a ratio of how strong two magnetic fields are. These fields are usually perpendicular to one another. Currents measured are typically proportional to the tangent of the same angle the needle goes through.


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Answer 3

A TG consists of a circular coil of insulated copper wire wound on a circular non magnetic frame. The frame is mounted vertically on a horizontal base provided with levelling screws on the base. The coil can be rotated on a vertical axis passing through its centre. A compass box is mounted horizontally at the centre of a circular scale. The compass box is circular in shape. It consists of a tiny, powerful magnetic needle pivoted at the centre of the coil. The magnetic needle is free to rotate in the horizontal plane. The circular scale is divided into four quadrants. Each quadrant is graduated from 0° to 90°. A long thin aluminium pointer is attached to the needle at its centre and at right angle to it. To avoid errors due to parallax a plane mirror is mounted below the compass needle.


[edit] Theory
When current is passed through the TG a magnetic field is created at its corners given by where I is the current in ampere, n is the number of turns of the coil and r is the radius of the coil.

If the TG is set such that the plane of the coil is along the magnetic meridian i.e. B is perpendicular to BH (BH is the horizontal component of the Earths magnetic field), the needle rests along the resultant. From tangent law, B = BHTanθ, i.e.


or


or I = KTanθ, where K is called the Reduction Factor of the TG.

Retrieved from "http://en.wikipedia.org/wiki/Tangent_galvanometer"

Answer 4

a type of galvanometer used to measur the earth magnetizing force

Answer 5

http://en.wikipedia.org/wiki/Tangent_galvanometer