Question

If current in the coil decreases, the strength of magnetic field
A. decreases
B. increases
C. sometimes decreases and sometimes increases
D. remains unchanged

Answer 1

Hint The above problem is based on the concept of the magnetic field. The magnetic field is the region around the current carrying conductor in which the other particles experience the effect of the magnetic force of the conductor. The strength of the magnetic field is also the same as the number of field lines at a point in the region.

Complete step by step answer
The formula for strength of the magnetic field is given as:
$B = \dfrac{{{\mu _0}I}}{{2\pi d}}$
Here, d is the distance of the point from the axis of the conductor, I is the current conductor.
From the above formula it can be said that the strength of the magnetic field depends on the current in the conductor and the distance of the point from the point.
The strength of the magnetic field is proportional to the current in the coil. If the current in the coil decreases then the strength of the magnetic field decreases.
Thus, the strength of magnetic field decreases on decrease in the current in the coil and the

option (A) is the correct answer.

Additional Information
The strength of the magnetic field is inversely proportional to the distance of the particle from the axis of the conductor, so the strength of the magnetic field can also decrease with increase in the distance between the conductor and particle.

Note The strength of the magnetic field also depends on the geometry of the conductor. The direction of the magnetic field also depends on the direction of the current in the conductor. The magnetic field is a vector quantity.