Methods of Changing the Magnetic Flux

For a coil of area A placed in a uniform magnetic field B, the magnetic flux is given by:

• \[\Phi=\vec{B}\cdot\vec{A}\]
• \[{\Phi=BA\cos\theta}\]

where θ is the angle between the area vector \[\vec A\] and the magnetic field \[\vec B\].

Magnetic flux through a coil can be changed in the following three ways:

When the coil is rotated in a magnetic field, the angle θ changes. Therefore, the magnetic flux through the coil changes.

The induced emf is:

• ε = BAω sin⁡ θ

where ω is the angular velocity of the coil.

Magnetic flux can also be changed by changing the effective area of the coil present in the magnetic field.

For example, when a frame or coil is moved towards the left or right in a magnetic field, the area of the frame within the field may change. Hence, the magnetic flux changes.

For a coil of fixed area and fixed orientation, magnetic flux can be changed by changing the magnetic field B.

• The induced emf is: ε = −Acos⁡ θ\[\frac {dB}{dt}\]