Question

Describe three different ways of creating an induced voltage (or current) from changing magnetic flux. I am looking for just a few lines of text, a sketch of each scenario, and an indication of which term in the magnetic flux equation is changing to produce the voltage (or current). Which method is the most practical for generating voltage at a power plant?

Answer 1

We know that magnetic flux is given as

magnetic flux = magnetic field * area

Therefore,

magnetic flux can be varied either by varying the magnetic field or by varying the area over time.

The area is usually varies by rotating a coil or loop in the magnetic field.

Magnetic flux is just a representation of how many field lines are passing through an area at a specific point of time.

More the lines, more will be the flux.

scenario 1

when magnetic field is changing

Now, as we can initially, no magnetic field lines passes though the loop, so there is no magnetic flux , hence no induced voltage or current. As the loop just enters the field, the magnetic flux will be produced due to change in magnetic field though the loop.

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Scenario 2

as the coil rotates in the constant magnetic field from electromagnets, it area vector normal to the field changes means the field lines also varies, so does magnetic flux is produced.

When the loop is perfectly normal to field lines, we have maximum flux. when loop is parallel to field, we have minimum flux.

Usually, second scenario is used to generate voltage at the power plant where a big core coil rotates between strong electromgnetic poles.