electromagnetic induction Flashcards
.State Faraday’s Law of Induction
.
Faraday’s Law of Electromagnetic induction states that the magnitude of
the induced emf in a circuit is equal to the time rate of change of magnetic
flux through the circuit
State Lenz’s law
.
the direction of induced emf is such that it will try to oppose the magnetic flux change or the cause that produces it
.Lenz’s Law is in accordance with the law of Conservation of Energy.
Justify.
The current induced in the coil is opposite to the direction of changing
magnetic flux. Then the bar magnet experiences a repulsive force due to the
induced current. Therefore, a person has to do work in moving the magnet.
This energy(work) is dissipated by Joule heating produced by the induced
current. Thus Lenz’s law is in accordance with law of conservation of
energy.
.What is motional emf?
When a conducting rod is moved through a constant magnetic field, an emf
is developed between the ends of the rod. This emf is known as Motional
Emf. 𝜺 = 𝑩𝒍𝒗
Define self induction
The phenomenon of production of induced emf in an isolated coil by
varying current through the same coil is called self-induction.
Define self inductance of a coil
The flux linked with the coil is proportional to the current through the coil.
𝜙α I
𝜙 = L I
where L is called self-inductance or coefficient of self-induction of the coil
Write the unit of inductance.
Henry(H)
Where do an inductor store energy?
An inductor store energy in the magnetic field
.Define mutual induction
The phenomenon of production of induced emf in a coil by varying the
current through a neighbouring coil is called mutual-induction.
Define mutual inductance of a coil
The flux linked with the coil is proportional to the current through the
neighbouring coil.
ϕ α I
ϕ = M I
where M is called mutual-inductance or the coefficient of mutual-induction
of the coil
The self-induced emf is also called the back emf . Why?
The self-induced emf is also called the back emf as it opposes any change in
the current in a circuit.
The electromagnetic analogue of mass is ……………………
Self inductance
.Derive the expression for mutual inductance of two co-axial solenoids
The current 𝐼2 in 𝑆2 sets up a magnetic flux
𝜙1 = 𝑁1𝐵2 𝐴1
𝜙1 = (𝑛1 𝑙) (𝜇0 𝑛2 𝐼2) 𝐴1
𝜙1 = 𝜇0 𝑛1𝑛2 𝐴1𝑙𝐼2 ————-(1)
But, 𝜙1 = 𝑀𝐼2 ————-(2)
From eq(1) and (2)
𝑀𝐼2 = 𝜇0 𝑛1𝑛2 𝐴1𝑙𝐼2
𝑴 = 𝝁𝟎 𝒏𝟏𝒏𝟐 𝐴1𝒍
self induction L=?
L=uN^2πr/2
