Physics · Class 12

AC generator

Rotating the coil changes its projected area in the magnetic field. Faster rotation raises both output frequency and peak EMF. Maximum flux occurs when instantaneous EMF is zero.

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AC generator

சுழலும் சுருளின் காந்தப்பாயம் மாறுவதால் AC உருவாகும். சுழற்சி வேகம் அதிகரித்தால் உச்ச EMF உயரும்.

Key notes, relationships and model limits

Key relationship

Φ=BA cosωt; ε=NBAω sinωt.

Remember

Rotating the coil changes its projected area in the magnetic field. Faster rotation raises both output frequency and peak EMF. Maximum flux occurs when instantaneous EMF is zero.

Common trap

Rotating flux creates a changing EMF; doubling angular speed also changes the waveform frequency.

Model limits

Uniform field, constant mechanical rotation, unloaded ideal generator; no losses.

What you will learn

Use the controls and plotted relation to explain ac generator.

Try the experiment

Try both scenarios, change one control, and predict the result before checking the graph and readouts.

Think of it this way

Change one input while keeping the others fixed, as you would in a controlled experiment.

Worked example

For N=100, A=100 cm², B=0.5 T and f=5 Hz, peak EMF≈15.71 V.

Why this matters

The model connects ac generator with an observable reading. Check the equation and assumptions before applying it.

Before you start

SI units · algebra · graph reading

Check your understanding

When flux is maximum in a rotating coil, instantaneous EMF is?

At its positive maximum.
Zero, because the flux slope is zero.
At its negative maximum.

Read the explanation

Zero, because the flux slope is zero.

Course connection: Class XII Chapter 7. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.