What is an electric motor . Explain prnciple construction and working
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An electric motor converts electrical energy into mechanical energy.
It works on the principle of the magnetic effect of current. A current-carrying coil rotates in a magnetic field. The following figure shows a simple electric motor.
When a current is allowed to flow through the coil MNST by closing the switch, the coil starts rotating anti-clockwise. This happens because a downward force acts on length MN and at the same time, an upward force acts on length ST. As a result, the coil rotates anti-clockwise.
Current in the length MN flows from M to N and the magnetic field acts from left to right, normal to length MN. Therefore, according to Fleming’s left hand rule, a downward force acts on the length MN. Similarly, current in the length ST flows from S to T and the magnetic field acts from left to right, normal to the flow of current. Therefore, an upward force acts on the length ST. These two forces cause the coil to rotate anti-clockwise.
After half a rotation, the position of MN and ST interchange. The half-ring D comes in contact with brush A and half-ring C comes in contact with brush B. Hence, the direction of current in the coil MNST gets reversed.
The current flows through the coil in the direction TSNM. The reversal of current through the coil MNST repeats after each half rotation. As a result, the coil rotates unidirectional. The split rings help to reverse the direction of current in the circuit. These are called the commutator.
It works on the principle of the magnetic effect of current. A current-carrying coil rotates in a magnetic field. The following figure shows a simple electric motor.
When a current is allowed to flow through the coil MNST by closing the switch, the coil starts rotating anti-clockwise. This happens because a downward force acts on length MN and at the same time, an upward force acts on length ST. As a result, the coil rotates anti-clockwise.
Current in the length MN flows from M to N and the magnetic field acts from left to right, normal to length MN. Therefore, according to Fleming’s left hand rule, a downward force acts on the length MN. Similarly, current in the length ST flows from S to T and the magnetic field acts from left to right, normal to the flow of current. Therefore, an upward force acts on the length ST. These two forces cause the coil to rotate anti-clockwise.
After half a rotation, the position of MN and ST interchange. The half-ring D comes in contact with brush A and half-ring C comes in contact with brush B. Hence, the direction of current in the coil MNST gets reversed.
The current flows through the coil in the direction TSNM. The reversal of current through the coil MNST repeats after each half rotation. As a result, the coil rotates unidirectional. The split rings help to reverse the direction of current in the circuit. These are called the commutator.
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Here is the answer
The given attachment shows the construction of an electric motor.
Structure:
Here,
A rectangular loop ABCD of copper wire with resistive coating is placed between the North Pole and South Pole of a strong magnet { Horseshoe magnet } such that the branches AB and CD are perpendicular to the direction of the magnetic field.
The ends of the loop are connected to the two halves , X and Y , of split rings - X and Y have resistive coating on their inner surfaces and are tightly fitted to the axle.
The outer conducting surfaces of X and Y are in contact with the two stationary brushes , E and F , respectively.
Working:
When the circuit is completed with the plug key or switch the current flows in the direction
E :arrow_right:A:arrow_right:B:arrow_right:C:arrow_right:D:arrow_right: F.
As the magnetic field is directed from the north pole to the South Pole the force on AB is downward and that on CD is upward by the Fleming's Left Hand Rule. Hence , AB moves downward and CD upward.
These forces are equal in magnitude and opposite in direction, Therefore, As observed from the side AD , the loop ABCD and the axle start rotating in anticlockwise direction.
After half rotation, X and Y come in contact with brushes F and E respectively and the current flows in direction E-D-C-B-A-F.
Hence, the force on CD is downward and that on AB is upward.Therefore , the loop and the axle continue to rotate in the anticlockwise dierection.
After every half rotation, the current in the loop is reversed and the loop and the axle start rotating in the anticlockwise direction.
When the current is switched off, the loop stops rotating after some time.
The given attachment shows the construction of an electric motor.
Structure:
Here,
A rectangular loop ABCD of copper wire with resistive coating is placed between the North Pole and South Pole of a strong magnet { Horseshoe magnet } such that the branches AB and CD are perpendicular to the direction of the magnetic field.
The ends of the loop are connected to the two halves , X and Y , of split rings - X and Y have resistive coating on their inner surfaces and are tightly fitted to the axle.
The outer conducting surfaces of X and Y are in contact with the two stationary brushes , E and F , respectively.
Working:
When the circuit is completed with the plug key or switch the current flows in the direction
E :arrow_right:A:arrow_right:B:arrow_right:C:arrow_right:D:arrow_right: F.
As the magnetic field is directed from the north pole to the South Pole the force on AB is downward and that on CD is upward by the Fleming's Left Hand Rule. Hence , AB moves downward and CD upward.
These forces are equal in magnitude and opposite in direction, Therefore, As observed from the side AD , the loop ABCD and the axle start rotating in anticlockwise direction.
After half rotation, X and Y come in contact with brushes F and E respectively and the current flows in direction E-D-C-B-A-F.
Hence, the force on CD is downward and that on AB is upward.Therefore , the loop and the axle continue to rotate in the anticlockwise dierection.
After every half rotation, the current in the loop is reversed and the loop and the axle start rotating in the anticlockwise direction.
When the current is switched off, the loop stops rotating after some time.
Attachments:
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