0Net flux through an area A having, under the magnetic influence of B, can be given as
Magnetic flux = ɸ = B. dA = BAcosΘ
Where, B = magnetic flux through an area
A = area under consideration
= angle between area vector and magnetic field vector.
- Case 1:
When the value of = 0
ɸ = BA
- Case 2:
When the value of = 90
ɸ = 0
Some important Properties as covered in our Class 12 Physics Chapter 6 Notes:
- Magnetic flux is denoted by ɸ.
- Flux is a scalar quantity.
- The SI unit of magnetic flux is Weber (Wb).
- The CGS unit of magnetic flux is maxwell or gauss.
- 1 Wb = 108 gauss.
- The dimensional formula of flux is [ ɸ ] = [M L2 T-2 A-2].
Electromagnetic Induction:
A fluctuating magnetic flux arises in a closed coil when a changing current is put across it. An emf is induced in the coil as a result of this flow. It generates an induced current as a result of the induced emf. Electromagnetic Induction is the phenomenon of creating induced emf or current due to changing flux.
Students are recommended to register on Extramarks’ website and access coursework and study resources such as Class 12 Physics Chapter 6 Notes, CBSE Extra Questions, CBSE Important Questions, etc. for a detailed explanation on electromagnetic induction.
Faraday’s Law of EMI:
There are two laws under Faraday’s Law of EMI.
- Law 1:
Law 1 states that whenever a change of magnetic flux is linked with any circuit, an emf is induced, which lasts as long as the change in magnetic flux continues.
- Law 2:
According to the Second Law, the magnitude of emf induced is directly proportional to the rate of change of magnetic flux.
∝ dɸ / dt
Therefore, induced emf = e = N (dɸ / dt)
Where N = number of turns pf coil
Induced Current:
Induced current = i = e/R = N/R (dɸ / dt)
Induced Charge:
Induced charge = dq = i dt = N/R (dɸ)
Induced charge is independent of time
Induced power = P = e2/R = N2/R (dɸ / dt)2
How to produce induced EMF:
EMF or electromotive force is induced in any circuit whenever there is a change in magnetic flux. But, this emf can be induced in many ways.
As magnetic flux = ɸ = BAcosΘ
Hence, flux ɸ can be changed when any B, A or is altered.
Therefore, the following ways can be used to induce EMF:
- By changing/ adjusting magnetic field B.
- By changing the area under consideration, A.
The area can be altered by stretching, shrinking or modifying the coil’s shape.
- By changing the angle .
This can be done by modifying the surface’s area and the magnetic field’s relative orientation.
Lenz’s Law:
According to Lenz’s Law, the direction of induced emf or current opposes the change in magnetic flux produced by it.
That is, e = -N (dɸ / dt)
Where N = number of turns
This Law is based on the conservation of energy.
Below is a short overview of how the magnetic field and magnetic force change according to the position of the magnet and the direction of the induced current. To get a better understanding of this law we recommend students to refer to our Class 12 Physics Chapter 6 Notes.
