Before using the tangent galvanometer, its coil is set in:
A. Magnetic meridian
B. Perpendicular to magnetic meridian
C. It does not require any setting

Hint: Tangent galvanometer is used to find out the presence of small current at a place having presence of magnetic field. It works on the principle of tangent law of magnetism which is used to find out the relation between two magnetic fields.

Complete step by step answer:
The tangent galvanometer works on the principle of tangent law of magnetism which is used to measure the strength between two magnetic fields present perpendicular to each other.
The tangent galvanometer has a coil of insulated copper wire wound around its magnetic frame. When we pass a current through the circular coil, as a result a magnetic field is generated at its center and in a direction, which is perpendicular to the plane of the coil.
We need to arrange the tangent galvanometer in such a way that the magnetic field generated is perpendicular to the Earth’s horizontal component of the magnetic field, $(B_H)$ and for that, the plane of the coil should be in a direction along $B_H$. Suppose the magnetic needle makes an angle $\theta$ with the magnetic meridian. Then, we can write that $B=B_H tan\theta$

So, the correct answer is “Option A”.

Additional Information:
Magnetic meridian resembles a vertical line passing through the magnetic axis of a freely suspended magnet. On the other hand, the geometric meridian, it resembles a vertical line which passes through a place and the geographic north and the south axis.

Note:
While using a tangent galvanometer, we generally take readings of both the ends of the pointer and then take its average to minimize the error. We also take dual readings by reversing the direction of current in the circular coil.