NEET Physics Notes Electromagnetic Induction-Concept of Electromagnetic Induction
Concept of Electromagnetic Induction
Concept of Electromagnetic Induction
Electromagnetic induction is the phenomenon due to which an induced emf is set up in a conductor or in an electric circuit, on changing the magnetic flux linked with it.
Magnetic Flux (ΦB)
The magnetic flux linked with a given surface area is defined as the total number of magnetic field lines (lines of induction) passing normally through the given area.
Mathematically, .
Magnetic flux is a scalar quantity. Outward magnetic flux is taken as positive
and inward flux is taken as negative
SI unit of magnetic flux is 1 weber (1 Wb), where,
Faraday’s Law of Electromagnetic Induction
According to the Faraday’s law, an emf is induced in a circuit whenever magnetic flux linked with that circuit changes (increases or decreases). The induced emf lasts so long as the change in magnetic flux continues.
The magnitude of the induced emf is equal to the rate of change of magnetic flux linked with the circuit i.e.
Lenz’s Law
This law states that the direction of the induced current in a circuit is so as to oppose the cause of change in the magnetic flux. Lenz’s law is strictly in accordance with the law of conservation of energy.
Motional Emf
Let a conducting rod of length l be moving with a uniform velocity v perpendicular to a l uniform magnetic field B, an induced emf is set up. The magnitude of the induced emf will be 
If the rod is moving such that it makes an angle 0 with the direction of the magnetic field, then 
Hence, for the motion parallel to B, the induced emf is zero.
When a conducting rod moves horizontally, then an induced emf is set up between its ends due to the vertical component of the earth’s magnetic field. However, at the magnetic equator, induced emf will be zero, because Bv = 0.
If during landing or taking off, the wings of an aeroplane are along the East-West direction, an induced emf is set up across the wings (due to the effect of BH).
Motional Emf in a Loop
If a conducting rod moves on two parallel conducting rails, then an emf is induced whose magnitude is 
and the direction is given by the Fleming’s right hand rule.
Induced current 
Rotational Emf
Let a conducting rod of length l rotate about an axis passing through one of its ends (that end may be fixed), with an angular velocity ω in a plane perpendicular to the magnetic field B, then an induced emf is set up between the ends of the rod, whose magnitude is given by
