With the help of neat diagram, explain the method to obtain unidirectional polarity in train lighting.

With the help of neat diagram, explain the method to obtain unidirectional polarity in train lighting.
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Answer :

Method to obtain unidirectional polarity in train lighting: Dynamo has rocker arm mounted on the shaft, friction tight. When the direction of rotation of the shaft is clockwise, terminal X (positive) touches P1 while terminal Y(negative) touches N. Thus, giving the output polarity as shown in figure. When the direction of rotation is anticlockwise, X (negative) terminal of the rocker arm will now touch to N1 brush and Y(positive) terminal of the rocker arm will touch to P . Thus, the output polarities will be obtained as shown in figure. Thus, unidirectional polarity is obtained.

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