EMI Flashcards
Magnetic Flux
total no. of MAGNETIC FIELD LINES crossing the surface normally
Si unit og M. flux is
weber or Tm^2
dimension of M. flux
[ML2T-2A-1]
from flux= BA/qv
define 1 weber
the magnetic flux produced when in a uniform M.F of 1 T acts normally to the area of 1 m^2
Faraday’s first law or EMI
whenever there is a relative motion between a magnet and a coil the magnetic flux linked with the coil changes and an emf is induced (current is induced) in it which lasts as long a change in the magnetic flux takes place
Faraday’s second law
the magnitude of induced EMF in a circuit is equal to the rate of change of magnetic flux linked with the circuit
Lenz law
the direction of EMF is always such that it opposes the cause that produces it
motional EMF
THE emf induced at the ends of conductor due to its motion in a magnetic field
lEl= B l v
power dissipated as joules heat and mechanical energy
B^2l^2v2^2/R
when does magnetic flux not change
- when a magnet and loop travel with the same velocity
- magnetic is rotated from its axis without change in distance from the loop
- loop moves in a uniform M.F AND the whole loop remains in it
mutual induction
the phenomenon in which an opposing emf is produced in a secondary coil as a result of a change in magnetic flux or current linked with the neighbouring coil
define henry in terms of mutual inductance
the mutual inductance between the coil is 1 Henry if current changes in a loop at a rate of 1A/s induces an emf of 1V in other coil
self inductance
The property of a coil by virtue of which it opposes the current flowing through the coil by inducing an emf in itself
coefficient of self inductance
the coefficient of self-inductance is equal to the number of flux linked with the coil when a unit current flows through it
unit of self-inductance
henry
or Wb/A
Tm2/A
1 Henry in terms of self inductance
The self-inductance of a coil is 1 Henry if current changes at the rate of 1 A/s through the coil which induces an emf of 1V in it
mutual inductance of 2 long axial solenoid
M = μoN1N2A2/l
self-inductance of long solenoid
L=μoN^2A/l
energy stored in an inductor
U= W= 1/2LI^1
what does mutual and self-inductance depend on
size and shape of coil
step up transformer
- electrical device for converting an AC at low voltage to high voltage
*Vi< Vo {voltage is increasing}
step down transformer
*an electrical device for converting an AC at high voltage to low voltage
*Vi>Vo {voltage is decreasing}
AC generator expression for emf and induced current
E=Eosinω t
I =Iosinωt
