Magnetism and Electromagnetism

Heating effect and lighting effect does not depend on the direction of current.

Oersted conducted an experiment to study the magnetic effect of electric current. In this experiment he observed the deflections of a compass needle placed in close proximity of an electric wire carrying current. He observed that in the absence of current the needle came to rest in Earths North-south direction under the influence of Earths magnetic field. However, when the needle was kept in close proximity of an electric wire carrying current it showed deflections in the east and west direction depending on the direction of current. Thus, indicating that the strength and direction of the magnetic field depends on the magnitude and direction of the current.

In his experiment Oersted observed that as the current in the wire increased, the deflection of the needle also increased, indicating that they are directly proportional.

Oersted conducted an experiment to study the magnetic effect of electric current. In this experiment he observed the deflections of a compass needle placed in close proximity of an electric wire carrying current. He observed that in the absence of current the needle came to rest in Earths North-south direction under the influence of Earths magnetic field. However, when the needle was kept below the wire and current was passed from A to B the north pole of the needle deflected towards the west and on reversing the direction of the current from B to A, it deflected towards the east. Similarly, when the needle was kept above the wire and current was passed from A to B the north pole of the needle deflected towards the east and on reversing the direction of the current from B to A, it deflected towards the west. This indicates that the direction of the magnetic field depends on the direction of current.

If electric current is passed through metal body then it behaves as magnet. passing an electric current through iron does not produce a magnet. But if you pass a direct current through a coil wound around the piece of iron, you will magnetize it. Passing a direct electric current through the same coil with no iron inside the coil will still produce a magnetic field that behaves just like a magnet. Similarly, passing a direct current through a coil around a piece of Bismuth will create the same magnetic field which behaves just like a magnet.

When a magnetic field is  applied, the cathode ray is  deflected from its normal  straight path into a curved path which can be identified by right hand thumb rule.

Above Curie temperature, ferromagnetic material become paramagnetic.

Electrons is an atom orbiting around nucleus possess orbital angular momentum. These orbiting electrons are equivalent to current-carrying loop and thus possess orbital magnetic moment. Diamagnetic substances are the ones in which resultant magnetic moment in an atom is zero. When magnetic field is applied, those electrons having orbital magnetic moment in the same direction slow down and those in the opposite direction speed up. Thus, the substance develops a net magnetic moment in direction opposite to that of the applied field.

At enough high temperature, a ferromagnet become a paramagnet. The domain structure disintegrates with temperature.

Here, $\chi =-1$
then $\mu _r=1+\chi \Rightarrow \mu _r=1+(-1)=I-1=0$
Since, magnetic susceptibility of given material is less than one. Hence, the given magnetic material is a diamagnetic material.

Diamagnetic substances induce magnetic field in the direction opposite to an external applied magnetic field and thus are repelled by external applied magnetic field.

diamagnetic
$-1 \leq x < 0$
$\chi =susceptibility$

Paramagnetic material $0< \chi < \varepsilon $
$\varepsilon $ it small, positive and less than one.
$\chi $ is suscepticity

Diamagnetic          Paramagnetic             ferromagnetic
-1 $\leq$ $\chi$ < 0            0 < $\chi$ < $\varepsilon$                 $\chi$ >>1
$\chi $$=$magnetic susceptibility