Electromagnetism

Electromagnetic Induction

Michael Faraday, an English Physicist is supposed to have studied the generation of electric current using magnetic field and a conductor.

When a conductor is set to move inside a magnetic field or a magnetic field is set to be changing around a conductor, electric current is induced in the conductor. This is just opposite to the exertion of force by a current carrying conductor inside a magnetic field. In other words, when a conductor is brought in relative motion vis-à-vis a magnetic field, a potential difference is induced in it. This is known as electromagnetic induction.

Fleming's Right Hand Rule

Electromagnetic induction can be explained with the help of Fleming's Right Hand Rule. If the right hand is stretched in a way that the index finger, middle finger and thumb are in mutually perpendicular directions, then the thumb shows the direction of movement of the conductor, index finger shows the direction of magnetic field and the middle finger shows the direction of induced current in the conductor. The directions of movement of conductor, magnetic field and induced current can be compared to three mutually perpendicular axes, i.e. x, y and z axes.

The mutually perpendicular directions also point to an important fact that the when the magnetic field and movement of conductor are perpendicular, the magnitude of induced current would be maximum.

Many of you may find it difficult to remember Fleming's Left Hand Rule or Right Hand Rule, because it can be quite confusing to correlate different fingers with different forces. What is common in both the rules is correlation between a particular finger and a particular force. In both the cases, index finger always shows the magnetic field. Middle finger always shows electric current and the thumb always shows the direction of motion.

Electromagnetic induction is used in the conversion of kinetic energy into electrical energy.

Electric generator:

Electric generator is a device which converts kinetic energy into electric energy. Battery is useful for generating power on a small scale. But whenever power generation is required on large scale, electric generator is the preferred device. In all the power plants, electric generator is used for producing electricity. Energy of flow of water or steam is utilized to move the turbine in order to generate electricity.

The structure of electric generator is similar to that of an electric motor. In case of an electric generator a rectangular armature is placed within the magnetic field of a permanent magnet. The armature is attached to wire and is positioned in way that it can move around an axle. When the armature moves within the magnetic field an electric current is induced. The direction of induced current changes, when the armature crosses the halfway mark of its rotation. Thus, the direction of current changes once in every rotation. Due to this, the electric generator usually produces alternate current, i.e. AC. To convert an AC generator into a DC generator, a split ring commutator is used. This helps in producing direct current.

AC and DC current:

AC – Alternate current: Current in which direction is changed periodically is called Alternate Current. In India, most of the power stations generate alternate current. The direction of current changes after every 1/100 second in India, i.e. the frequency of AC in India is 50 Hz. AC is transmitted upto a long distance without much loss of energy is advantage of AC over DC

DC – Direct current: Current that flows in one direction only is called Direct current. Electrochemical cells produce direct current.

DC current faces reduction in voltage during long distance transmission. This problem is solved by using AC current. So, AC current is ideal for long distance transmission. The current from power plants is supplied to households, factories and other establishments, in the form of AC current. This helps in preventing loss of power during long distance transmission.