InterviewSolution
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InterviewSolution
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Explain the underiyingand working of an electric generator by drawing a labelled diagram. What is the function of brushes ? |
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Answer» Solution :Principle : An electric generator works on the principle of electromagnetic induction. When a coil is rotatedbetween the magnet or when the magnet is rotated in and out of the coil , a current is INDUCED in thecoil in a direction given by Fleming.sright-hand RULE. Construction: An AC electric generatorconsists of a rectangularcoil ABCD placed between two poles of a permanent magnet asshown in the figure. The ends of the coil are connected to rings `R_(1) and R_(2)` . The inner sides of the RING are insulated and are attachedto an axle. Theirouter side is made conducting and is in contact with two brushes `B_(1) and B_(2)`whichare connected to a galvanometerthrough wires. Working : The axle attached to the two rings is rotated such thearm AB moves up and arm CD moves down in the magnetic field produced by the permanent magnet, i.e., ABCD is rotated clockwise. Then, by Fleming.s right-hand rule, the inducedcurrents are set up in these arms and current flowsin the direction ABCD and from `B_(2) t o B_(1)` as indicated by deflection inthe galvanometer. After half a rotation, arm CD starts moving up and ABmoves down. Then, the induced current flows along DCBA, and from `B_(1) t o B_(2)`externally . After every half rotation the POLARITY of the currentchanges thereby producing alternating current (AC). Thus, the device is called an AC generator. The function of the brushes is to transmit current induced externally from coil ABCD to the external circuit. 
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