Tag: magnetic effects of electric current

Magnets are also used in making electric generators and electric motors. Magnetic resources imagine also use magnets

AC generator means alternating generator. i.e. AC generator produces current that revenues its direction continuously.

A small generator is called or dyanamo. Ex. Dynamo are used in bicycles for lighting purposes.

Electric Motor
1. It converts electrical energy into mechanical energy.
2. It needs electrical energy for its working.
3. They are used as water pumps, marble grinders e.t.c Generator
1. It converts mechanical energy into electrical energy
2. It needs mechanical energy for its working.
3. They are used as water pumps, marble grinders e.t.c
3. Diesel generator, hydro-electric generator are the examples of it.

Dynamo produces Direct current by process of commutation.

When a conductor moves in a magnetic field, an emf is induced across the conductor. This is the only basis on which each and every rotating electric generator works. Let us discuss the matter in a little bit details so that we can easily understand how does an electrical generator actually work. According to Faraday's law of electromagnetic induction, when a conductor links with a changing flux, it will have an induced emf across it. The value of induced emf across the conductor depends on the rate of change of flux linkage with the conductor. 

When the plane of the rectangular coil is parallel to the magnetic field, angle between the magnetic field and the area vector of coil  $\theta = 90^o$
Flux passing though the coil  $\phi = BA \ \cos\theta = BA \ \cos90^o = 0$
Thus no emf is induced in the coil and induced current is zero.

Carbon brushes are not necessary in a dynamo, if the coil remains stationary and the magnet moves, because It is not necessary to reverse the direction of the current.The brushes transfer the electricity from outside the motor to the spinning winding in the center of the motor. They undergo quite a lot of friction, and after a while wear out. Carbon is used as it is a reasonable conductor, and is soft enough to wear down instead of wearing down the "comutator" - the ring the brushes press against. Brushes are designed to be replaceable in large motors because of this.

A small AC dynamo is connected to a galvanometer and gently rotated, then the needle of the galvanometer moves towards both right and left The deflection of the needle of a galvanometer indicates a current flowing through the small stator winding (wound coil) inside the device. The more current flowing through the coil the greater the magnetic disturbance