50 points question
describe the principle and working of DC generator and electric motor ..?
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Answers
Working principle of a DC generator: According to Faraday's laws of electromagnetic induction, whenever a conductor is placed in a varying magnetic field (OR a conductor is moved in a magnetic field), an emf (electromotive force) gets induced in the conductor.
Working: When a current is allowed to flow through the coil PQRS the coil starts rotating anti-clockwise. This happens because a downward force acts on length PQ and at the same time, an upward force acts on length RS. As a result, the coil rotates anti-clockwise.
Current in the length PQ flows from P to Q and the magnetic field acts from left to right, normal to length PQ. Therefore, according to Fleming’s left hand rule, a downward force acts on the length PQ. Similarly at an upward force acts on the length RS. These two forces cause the coil to rotate anti-clockwise.
When coil complete half rotation, the position of PQ and RS interchange. The half-ring D comes in contact with brush A and half-ring C comes in contact with brush B. therefore the direction of current in the coil PQRS gets reversed. Now the current flows through the coil in the direction SRQP.The direction of current through the coil PQRS reverse after every half rotation. As a result, the coil rotates in same direction. The split rings help to reverse the direction of current in the circuit. These are called the commutator.
I hope this may help u
Answer:
Dc generator
A dc generator is an electrical machine which converts mechanical energy into direct current electricity.
Principle
A DC generator produces direct power based on fundamental principle of Faraday's laws of electromagnetic induction. According to these laws, when a conductor moves in a magnetic field it cuts magnetic lines force, due to which an e.m.f is induced in the conductor
Working
According to Faraday’s laws of electromagnetic induction, whenever a conductor is placed in a varying magnetic field (OR a conductor is moved in a magnetic field), an emf (electromotive force) gets induced in the conductor. The magnitude of induced emf can be calculated from the emf equation of dc generator. If the conductor is provided with a closed path, the induced current will circulate within the path. In a DC generator, field coils produce an electromagnetic field and the armature conductors are rotated into the field. Thus, an electromagnetically induced emf is generated in the armature conductors. The direction of induced current is given by Fleming’s right hand rule.
Need of a Split ring commutator:
working of DC generator
According to Fleming’s right hand rule, the direction of induced current changes whenever the direction of motion of the conductor changes. Let’s consider an armature rotating clockwise and a conductor at the left is moving upward. When the armature completes a half rotation, the direction of motion of that particular conductor will be reversed to downward. Hence, the direction of current in every armature conductor will be alternating. If you look at the above figure, you will know how the direction of the induced current is alternating in an armature conductor. But with a split ring commutator, connections of the armature conductors also gets reversed when the current reversal occurs. And therefore, we get unidirectional current at the terminals
Electric motor
An electric motor is an electrical machine that converts electrical energy into mechanical energy.
Principle
The principle of the electric motor is based on the fact that a current carrying conductor produces a magnetic field around it. A current carrying conductor placed perpendicular to magnetic field experiences a force.
Working
When electric current is passed into the rectangular coil, this current produces a magnetic field around the coil.
The magnetic field of horse shoe-type magnet then interacts with the magnetic field of the coil and causes the coil to rotate continuously.
If ABCD is in horizontal position current from battery enters the coil through brush B _{ 1 }, and commutator half ring C:. The current flows in the direction ABCD
and leaves via ring and brush B _{ 2 }
The direction of current is from A to B, the direction of current is from C to D. The force on side AB of the coil is in the downward direction. Whereas the force on the side CD of the coil is in the upward direction. ABCD rotate in anti-clockwise direction.
While rotating when the coil reaches vertical position then the brushes B _{ 1 } and B _{ 2 } will touch the gap between the commutator rings and current to the coil is cut off. But the coil does not stop rotating because it has already gained momentum.
The coil CD comes on the left side and AB comes to the right side. Again they come in contact with brush B _{ 1 } Current direction is reversed.
The reversing of current in the coil is repeated after every half rotation due to which the coil continue to rotate as long as current from the batter is passed through it. The rotating shaft of electric motor can drive a large number of machines which are connected to it.
May it helps you