CBSE Class 12 · 2007 · Alternating CurrentShort Answer

Draw a labelled diagram of an a.c. generator. Explain briefly its principle and working.

Answer: Principle: electromagnetic induction; a coil rotating in a magnetic field develops $e = N B A ω sin ω t$ .

Solution

Principle: An a.c. generator is based on electromagnetic induction — the emf induced in a coil rotating in a magnetic field.
Working: A coil of

N

turns and area

A

rotates with angular speed

ω

in a uniform field

B

. The flux linked is

ϕ = N B A cos ω t

, so the induced emf is

e = - \frac{d ϕ}{d t} = N B A ω sin ω t = e_{0} sin ω t

As the coil turns, each side moves alternately up and down through the field, reversing the current every half rotation; slip rings and brushes deliver this alternating emf to the load. The essential parts are the field magnet, the armature coil, slip rings and brushes.

e = e_{0} sin ω t, e_{0} = N B A ω

CBSE Class 12 Board · 2007 · Subjective

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CBSE Class 12 · 2007 · Alternating CurrentShort Answer

Solution

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