Magnetic Effect of Electric Current Part-1

Magnetic Effect of Current


Hans Christian Oersted, played a crucial role in understanding electromagnetism. In 1820 he accidentally discovered that a compass needle got deflected when an electric current passed through a metallic wire placed nearby.  Through this observation Oersted showed that electricity and magnetism were related phenomena. His research later created technologies such as the radio, television and fiber optics. The unit of magnetic field strength is named the oersted in his honor.

Magnetic Field:

The magnet exerts its influence in the region surrounding it is called magnetic field

Therefore the iron filings experience a force. The force thus exerted makes iron filings to arrange in a pattern. The region surrounding a magnet, in which the force of the magnet can be detected, is said to have a magnetic field.

Magnetic Field Lines:

The lines along which the iron filings align themselves represent magnetic field lines

Properties of Magnetic Field Lines:

1. Magnetic field is a quantity that has both direction and magnitude.

2. The direction of the magnetic field is taken to be the direction in which a north pole of the compass needle moves inside it.

3. Inside the magnet, the direction of field lines is from its south pole to its north pole. Thus the magnetic field lines are closed curves.

4. The field is stronger, that is, the force acting on the pole of another magnet placed is greater where the field lines are crowded.

5. No two field-lines are found to cross each other. If they did, it would mean that at the point of intersection, the compass needle would point towards two directions, which is not possible.



Magnetic Field inside a Current StraightConductor:

What happens to the deflection of the compass needle placed at a given point if the current in the copper wire is changed?

Vary the current in the wire. The deflection in the needle also changes. In fact, if the current is increased, the deflection also increases. It indicates that the magnitude of the magnetic field produced at a given point increases as the current through the wire increases.

What happens to the deflection of the needle if the compass is moved away from the copper wire but the current through the wire remains the same?

Now place the compass at a farther point from the conducting wire .We see that the deflection in the needle decreases. Thus the magnetic field produced by a given current in the conductor decreases as the distance from it increases.  It can be noticed that the concentric circles representing the magnetic field around a current-carrying straight wire become larger and larger as we move away from it.

Right hand Thumb Rule

Imagine that you are holding a current-carrying straight conductor in your right hand such that the thumb points towards the direction of current. Then your fingers will wrap around the conductor in the direction of the field lines of the magnetic field.This is known as the right-hand thumb rule.