Explain the underlying principle and working of electric generator by drawing a labelled diagram. What is the function of brushes?
Mechanical energy is converted to electrical energy in an electric generator. The working principle of an electric motor is Fleming's right hand rule.
Electric current is induced in an insulated copper coil when it is forced to rotate in a magnetic field. Circuit diagram of a simple AC generator is shown in the figure. If axle X is rotated clockwise, then the length PQ moves upwards and the length RS moves downwards.
Since the lengths PQ and RS are moving in a magnetic field, a current will be induced due to electromagnetic induction. Length PQ is moving upwards and the magnetic field acts from left to right. According to Fleming's right hand rule, the direction of induced current will be from P to Q. Similarly, the direction of induced current in the length RS will be from R to S. The direction of current in the coil is PQRS. Hence, the galvanometer shows the deflection in a particular direction. After half a rotation, length PQ starts moving down whereas length RS starts moving upward. The direction of the induced current in the coil gets reversed as SRQP. As the direction of current gets reversed after each half rotation, the produced current is known as alternating current (AC). To get a unidirectional current, instead of two slip rings, two split rings are used, as shown in attached figure.
In this arrangement, brush A always remains in contact with the length of the coil that is moving up whereas brush B always remain in contact with the length that is moving down. The split rings C and D act as commutator. The direction of current induced in the coil will be PQRS for the first half and SRQP for second half of rotation. Thus a unidirectional current is produced from generator called as DC generator.
Mechanical energy is converted to electrical energy in an electric generator. The working principle of an electric motor is Fleming's right hand rule.
Electric current is induced in an insulated copper coil when it is forced to rotate in a magnetic field. Circuit diagram of a simple AC generator is shown in the figure. If axle X is rotated clockwise, then the length PQ moves upwards and the length RS moves downwards.
Since the lengths PQ and RS are moving in a magnetic field, a current will be induced due to electromagnetic induction. Length PQ is moving upwards and the magnetic field acts from left to right. According to Fleming's right hand rule, the direction of induced current will be from P to Q. Similarly, the direction of induced current in the length RS will be from R to S. The direction of current in the coil is PQRS. Hence, the galvanometer shows the deflection in a particular direction. After half a rotation, length PQ starts moving down whereas length RS starts moving upward. The direction of the induced current in the coil gets reversed as SRQP. As the direction of current gets reversed after each half rotation, the produced current is known as alternating current (AC). To get a unidirectional current, instead of two slip rings, two split rings are used, as shown in attached figure.
In this arrangement, brush A always remains in contact with the length of the coil that is moving up whereas brush B always remain in contact with the length that is moving down. The split rings C and D act as commutator. The direction of current induced in the coil will be PQRS for the first half and SRQP for second half of rotation. Thus a unidirectional current is produced from generator called as DC generator.
