How Electricity Produces a Magnetic Field

This article discusses the magnetic effects of electricity, how it is formed, and the theory supporting it.

In 1820, a Danish physicist named Hans Christian Oersted observed that the flow of a current through a wire causes the deflection of a nearby magnetic needle. This was a strong indication that the generation of a magnetic field is associated with the flow of electrons through a conductor.

Magnetic Effect Of Electricity:

How to detect a magnetic field around a straight conductor carrying current:

A smooth sheet of cardboard with iron filings spread over is fixed in a horizontal plane with the help of a clamp. A straight wire passes through a hole made at the center of the cardboard.

A current passes through the wire when its two ends are connected to a battery. When the cardboard is gently tapped, we can observe that the iron filings arrange themselves along concentric circles. This clearly shows that a magnetic field is developed around the current carrying conductor.

To find the direction of the magnetic field, let us imagine a straight wire passing through the plane of the paper and perpendicular to it. A compass needle is then placed in such a way that its axis is always tangential to the plane of the circular magnetic field around the conductor. The compass is then left at rest.

When the current is inward, the direction of the magnetic field around the conductor is clockwise.

When the current direction is reversed - that is outward - the direction of the magnetic pole of the compass needle also changes showing the reversal of the direction of magnetic field. Now, the direction of the magnetic field is counterclockwise.

These facts prove that the direction of the magnetic field depends on the direction of the current in conductor. This is given by Maxwell’s rule.

Magnetic Field around a Straight Conductor Carrying Current:

Right Hand Grip Rule

Law Supporting the Magnetic Effect of Electricity.

Maxwells’s Right Hand Corkscrew Rule:

If a right hand corkscrew is rotated along the direction of the current flow, then the direction of screw rotation gives the direction of the magnetic lines of force around the conductor. The direction of the magnetic field can also be determined by using the right hand grip rule (see image above).