CBSE Class 12 Physics 2016 Outside Delhi Set 1 Paper

Question : 23

Total: 26

SECTION -D

Ram is a student of class X in a village school. His uncle gifted him a bicycle with a dynamo fitted in it. He was very excited to get it. While cycling during night, he could light the bulb and see the objects on the road. He, however, did not know how this device works. He asked this question to his teacher. The teacher considered it an opportunity to explain the working to the whole class.
Answer the following questions:
(a) State the principle and working of a dynamo.
(b) Write two values each displayed by Ram and his school teacher.

Solution:

(a) Principle and working
(b) Two values, each, displayed by
(i) Ram
(ii) School teacher
(a) Principle:
Whenever a coil is rotated in a magnetic field, an emf is induced in it due to the change in magnetic flux linked with it.
Working-
As the coil rotates, its inclination (θ) with respect to the field changes. Hence sinusoidal/ varying emf (=e0sin‌ωt) is obtained./May also be explained graphically.

[Note-Give full marks if the student obtains the expression for induced emf mathematically.]
(b) Values:
Ram-Scientific aptitude, curiosity, keenness to learn, positive approach, etc (any two)

Teacher-
Dedication, concern for students, depth of knowledge, generous, positive attitude towards queries, motivational approach.

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