Electromagnetic induction Flashcards
Magnetic flux
BAcos(theta)
unit is weber
dimentional unit for magnetic flux
[M L^2 A^-1 T^-2]
what is electromagnetic induction
inducing electricity by magnetism
what is the motion which is responsible for the generation of electric current in the coil?
relative motion
faraday first law of electromagnetic induction
when a magnetic field changes, it induces an electromotive force (EMF) in a conductor
faraday second law of electromagnetic induction
1)The magnitude of the induced emf is equal to the rate of change of magnetic flux linked with the closed circuit
2)EMF= - (dΦ/dt)*N
Flux can be varied by changing
(i) The shape of the coil (A changes)
(ii) The strength of the magnetic field (B changes)
(iii) The orientation of the coil (0 changes)
Lenz’s Law
the direction of induced current is such that it opposes the cause which produces
when a north pole of a magnet is brought near a loop it induce the current in the direction of
anti clockwise
when a south pole of a magnet is brought near a loop it induce the current in the direction of
clockwise
motional EMF
Blv
l==>length
v==>velocity
EMF induced in self inductance
E= - d(Nφ)/dt = - d(LI)/dt
EMF induced in mutal inductance
E= -d(Nφ)/dt = - d(MI)/dt
Inductance depends on
1) geometry of coil
2) intrinsic material property
mutual inductance when I2 current is setup to S2
M12= μn1n2* lpi(R1)^2
where
n1–>no of turns in coil 1
n2–>no of turns in coil 2
l–> length of coil 1
R1–> radius of coil 1
m12=
m21
in mutual inductance the emf induced depends on
1) rate of change of current
2) mutual inductance of the coil
self inductance (L) Formula
L=μn^2A*l
where
n–> no of turns
A–> cross sectional area
l–> length of solenoid
what is the direction of induced current in self inductance
opposite to the source current
what do you mean by self inductance
Self-inductance is the property of the current-carrying coil that resists or opposes the change of current flowing through it
work done in self inductance
W=1/2LI^2
where
L–> self inductance
I–> current
! This stored as magnetic potenial energy
The value of the voltage generated on ac gererator depends on
1)The number of turns in the coil.
2)strength of the magnetic field.
3)The speed at which the coil or the magnetic field rotates.
EMF produced in ac generator
emf=wNBA sin(wt)
w–>angular velocity
wNBA–> MAX emf
