Chapter-4|Moving Charges and Magnetism| NCERT 12th Physics:
Magnetic Field Due to a Current Carrying Conductor:
Magnetic Field On The Axis of a Circular Current Carrying Loop:
Let we consider a circular loop of radius R with Centre C.
Let we consider current element Idl on the top and the bottom.
Now, magnetic field at point P due to current element Idl, According to Biot-Savart’s law
Now, Resolving dB due to current element Idl at top and bottom balance each other. The net magnetic field is obtained only by the Sine component.
Note: When the direction of current in the coil is anti-clockwise, then direction of magnetic field is away from the loop.