Electromagnetic Induction Flashcards
EMI
Phenomenon of production of induced EmF due to which magnetic Flux linked with a closed circuit
Faraday’s law
Magnitude of induced emf is equal to time rate of change of magnetic Flux linked with thr closed circuit
E = -Ndø/dt
Flux can be varied by
Changing A,B or ø
Magnetic flux
Total no of field lines crossing the surface normally
Ø(B) = B.A
Flux unit
Weber
Gauss’s law of magnetism
Total magnetism Flux throug hany closed system is 0
Ø(b) = sigma B.A = 0
Lenz’s law
Polarity of induced emf is such that it tends to produce a current which opposes change in Flux that produced it
When fluc changes from Øa to Øb in time t, avg Emf E=
E = -N(Øb-Øa)/t
Motional EMF
Emf induced across the ends of a conductor due to its motion in B
Motional emf E=
BlV where dx/dt = -V in decreasing dir of x
Motionless emf from Lorentz force & energy consideration
E = VBl
Motional emf I =
BlV/R
Motional emf F =
B²l²V/R
Motional emf P =
FV = B²l²V²/R = powerloss[P(j)]
Mechanical energy is converted to
Electrical energy then to thermal energy. So energy I’d conserved
Inductance
Phenomenon of production of induced emf in a coil by changing current through itself or neighbouring coil
Inductance fm
Nø = KI where K is inductance
Self Inductance + fm
Phenomenon of inducing EMF in a coil by changing I through itself
NØ = LI
Self Inductance by Faraday’s law
E = -LdI/dt
-ve sign is because self induced emf opposes change in current through itself(back emf)
Self Inductance of a long solenoid
L = myu°N²/l pi r²
Self Inductance depends on:
N²(turns)
Area
Myu
Slope of Ø-I graph gives
Self inductance
Mutual inductance + fm
Phenomenon os inducing emf in a coil by changing current through te neighboring coil
NØ = mI
Emf by faraday’s law for mutual inductance
E = -mdI/dt
-ve as Ø opposes emf
Mutual inductance of 2 long solenoids
m = myu°n1n2L pi r²
Mutual inductance depends on
M prop N1N2(Turns)
M prop A (Area)
M prop 1/l distance btw solenoids
Relative orientation changes as we rotate it
Inductive coupling
When I flows through 2 nearby coils simultaneously, Flux linked with 1 coil will be sum of fluxes which exists independently
E1 = -LdI1/dt - MdI2/dt
N1Ø1/I2 = N2Ø2/I1
Coefficient of coupling k of 2 coils
K = m/(L1L2)½
Energy stored in an inductor
E = ½LI²
AC generator
Converts mechanical energy to electrical energy
Principle: change in Flux induces emf in it
AC generator emf
E = E°sinwt(E°=wNBA)
E° = amplitude of induced emf
Alternating emf & alternating current
Direction of induced emf and current varies periodically with time
E = E°sin(2pi nyu t)
Factors on which mutual inductance depends on
N
Area
Distance btw solenoids(inversely)
Relative orientation
