Electricity and magnetism equations physics@tutorvista.com gas city indiana post office


Faraday and Henry performed lots of experiments to learn about the connection between electricity and magnetism. The results of these experiments have led to the life styles of today’s men, who made life easy by using lots of electrical applications.

A solenoid is connected to a sensitive galvanometer. On moving a magnet towards a coil, the galvanometer shows a deflection. When the magnet is reversed, the deflection is seen to be in the opposite direction. Once the magnet is stopped, there is no deflection in galvanometer. On moving the magnet faster towards the coil, the deflection is longer.

Similar results are obtained when the magnet is kept stationary and the coil is moved. It means that whenever a current was induced in the coil there is a relative motion between the coil and the magnet. The magnitude of the current depended on the strength of the magnet and also on the magnitude of their relative velocity.

Similar results were seen when the magnet is replaced by as coil connected to a battery. Even without physically moving the coils a current was shown in the galvanometer only when the switch is on and when the current is put off i.e., when the current is building up in the coil or when it reduced to zero the galvanometer in the other coil showed a charge.

This current, which is produced in the coil connected to the galvanometer, is called as induced current. The induced currents direction, when the current builds up in the other coil was opposite to that when the current reduced opposite to that when the current reduced. The deflections were momentarily seen only when the switch was opened and closed. These observations can be summarized in Faraday’s laws of electromagnetic induction.

Diamagnetism: Diamagnetism is the property of an object which causes it to create a magnetic field in opposition to an externally applied magnetic field, thus causing a repulsive effect. If we consider the electrical nature of the Diamagnetic material we will find that it does not have unpaired electrons because of which bulk effect is not produced by the magnetic moments of the electrons. In diamagnetic materials, magnetization is due to the orbital motion of the electrons.

Paramagnetism: Paramagnetism is a form of magnetism that occurs only in the existence of an externally applied magnetic field. As supported by the Pauli exclusion principle, compound atoms of the elements have some inner electron shells that are incomplete, causing their unpaired electrons to spin like tops and orbit like satellites, thus making the atoms a permanent magnet tending to align with and hence strengthen an applied magnetic field. When external magnetic field is applied to the Paramagnetic materials they tend to align in the direction of the applied magnetic field and reinforce the external magnetic field applied.

Ferromagnetism:Ferromagnetic effects are very large; producing magnetizations sometimes greater than the applied field that are much larger than either diamagnetic or paramagnetic effects. Ferromagnetic materials also have unpaired electrons and exhibit a long-range ordering phenomenon at the atomic level which causes the unpaired electrons spin and maintain a parallel orientation to each other even if we remove the applied field. After the temperature the ferromagnetic materials lose their ferromagnetic properties, because of the disorder due to the high temperature. Examples are: cobalt, iron, nickel etc.

Antiferromagnetic materials spontaneously align themselves at relatively low temperatures into opposite, or antiparallel, arrangements throughout the material so that it exhibits almost no gross external magnetism. As a result Antiferromagnetic materials effective magnetic moment is zero. This property of the materials is called antiferromagnetism and the materials which exhibit this are called antiferromagnetic materials. An example of Antiferromagnetic materials is spin glass. → Read More