Magnetic Field Pattern due to a Circular Loop (or Circular Wire) Carrying Current
- When current is passed through a straight wire, a magnetic field is produced around it.
- It has been found that the magnetic effect of current increases when the wire is converted into a circular loop
- The magnetic field lines are circular near the current-carrying loop.
- As we move away, the concentric circles representing magnetic field lines become bigger and bigger.
- At the centre of the circular loop, the magnetic field lines are straight
- By applying right hand thumb rule, it can be seen that each segment of circular loop carrying current produces magnetic field lines in the same direction within the loop.
- At the centre of the circular loop, all the magnetic field lines are in the same direction and add each other, due to which the strength of magnetic field increases.
The magnitude of magnetic field produced by a current-carrying circular loop (or circular wire) at its centre is :
- directly proportional to the current passing through the circular loop
- inversely proportional to the radius of circular loop (or circular wire).
- The strength of magnetic field can be increased by taking a circular coil consisting of a number of turns of insulated copper wire closely wound together.
- if there is a circular coil having n turns, the magnetic field produced by this current-carrying circular coil will be n times as large as that produced by a circular loop of a single turn of wire.
According to Clock face rule, look at one face of a circular wire (or coil) through which a current is
(i) if the current around the face of circular wire (or coil) flows in the Clockwise direction, then that face of the circular wire (or coil) will be South pole (S-pole).
(ii) if the current around the face of circular wire (or coil) flows in the Anticlockwise direction, then that face of circular wire (or coil) will be a North pole (N-pole)
if the direction of current in the front face of a circular wire is clockwise, then the direction of current in the back face of this circular wire will be anticlockwise (and vice versa)