Correct option is
B 
Magnetic field due to the circular current (I) carrying coil of radius 
, at a distance 
from the center of the coil is given by:
![\[B_{1}=\frac{\mu_{0}}{4 \pi} \frac{2 \pi a^{2} I}{\left(z^{2}+a^{2}\right)^{3 / 2}}\]](https://www.learnatnoon.com/s/wp-content/ql-cache/quicklatex.com-c5cc9c1bcef1a682d6a07a150dea36c5_l3.png "Rendered by QuickLaTeX.com")
Now the field at a point 
times the field at the center:
So, 
or, 
for, 
An electric current i is flowing in a circular coil of radius a. At what distance from the center of the axis of the coil will the magnetic field be 
of its value at the centre?
A
в
c
D
of its value at the centre? A
в
c
D
An electric current i is flowing in a circular coil of radius a. At what distance from the center of the axis of the coil will the magnetic field be of its value at the centre?
A
в
c
D
of its value at the centre? A
в
c
D
.
)
west of the geographic north. The north tip of the magnetic needle of a dip circle placed in the plane of magnetic meridian points above the horizontal. The horizontal component of the earth’s field is measured to be 
Specify the direction and magnitude of the earth’s field at the location.At a certain location in Africa, a compass points 
and 
carrying currents of 
and 
in the same direction are separated by a distance of 
. Estimate the force on a 
section of wire A.
wire carrying a current of 
is placed inside a solenoid perpendicular to its axis. The magnetic field inside the solenoid is given to be 
. What is the magnetic force on the wire?
and making an angle of 
with the direction of a uniform magnetic field of 
. What is the magnitude of the field 
at a point 
from the wire?
-turns carrying current 
.
is at distance 
from the wire. Find the force acting on the electron if its velocity is directed towards the wire.