Concepts of Physics

IIT JEE Physics (1978-2018: 41 Years) Topic-wise Complete Solutions

Generating Energy with a Turbine

Introduction

The DC motor can be used as a generator. The emf is generated in the motor coil when its shaft is rotated fast. This emf can be detected by a galvanometer.

Apparatus

DC motor, galvanometer, turbine fan etc

Procedure

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Cut small rectangular strip from a can to make blades of a turbine. Make cuts on the edge of a round plastic lid (cover) and fix the blades in them with a glue, as shown. Fix a small length of tube (from the refill of a pen) at the centre of the lid. Slide its free end over the shaft of a motor from a toy. If you blow on the blades of your turbine, it will rotate, and so will the shaft of the motor. The turbine will also rotate when steam from a kettle or a jet of water falls on its blades.

Since DC motors and generators are similar in construction, your motor acts as a generator when its shaft is rotated. You will detect a current by connecting its wires to a sensitive galvanoscope or milliammeter. With a powerful motor, you will be able to light an LED.