electromagnetic Induction:
The Production of Electromotive force in a conductor when
there is a change in the magnetic flux linkage with coil or
when there is a relative motion of the conductor across a
magnetic field.
Magnetic Flux:
Magnetic Flux through an area dS in a magnetic Field B is
= 
B.dS
Faraday's Law:
When the Flux of a magnetic field through a loop changes,
an emf is induced in the loop which is given by :
= -d/dt
Where
= B.dS is the Flux through the loop.
The EmF lasts as long as the magnetic Field changes.
Lenz's Law:
It states that the polarity of the induced Emf and the
direction of the induced current is such tat it opposes the
change that has induced it.
Motional Emf:
When a conducting rod of length L moves with a velocity V
in a magnetic field B such that B,V & L are mutually per-
-pendicular to each other then the induced Emf is :
= BLV
This is called as motional Emf.If the circuit is completed
the direction of the current can be worked out by Lenz's
Law.
Induced Electric Field:
A time varying Magnetic field induces an electric field.If
a conductor is placed in this field , an induced Emf is
produced :
= E.dL (Here is Cyclic Integral)
= - d/dt
E.dL = - d/dt (Cyclic Integral)
Self Induction:
A Current Carying loop produces a magentic Flux Through
the area.
= Li Where L is the Self Inductance.
If Current Changes in the loop the Induced Emf is given
by:
= - d/dt = -L di/dt
For a Solenoid of n turns,
= -n d/dt B.dS
Self Inductance of a long solenoid is:
L = 
r0n2LA
Where
r is the relative magnetic permeability of the core , n is
no. of turns per unit length , L is the length of solenoid.
and A is the cross-sectional area of the solenoid.
Mutual Inductance:
A changing current in one circuit causes a changing Flux &
hence an induced Emf in a neighbouring circuit.
N22 = Mi1
Where M is the Mutual Inductance of coils 1 2
M = N22/i1 = N11/i2
1 = -M di1/dt
2 = -M di2/dt
Alternating Current and Voltage:
Current and Voltage varying Sinusoidally are called as AC
and AV (Alternating Current and Voltage)
V = V0Sin
t
i = i0Sint
Mean Values of Voltage and Current:
(a)In one complete cycle:
V = 0 , i = 0
(b)In Half Cycle:
V = 2V0/
, i = 2i0/
(c)Root mean square Values:
Vrms = V0/
2
irms = i0/2
Where V0 and i0 are peak Voltage and current.
AC Circuit with a Resistor:
E = E0Sint = E0Sint/R
AC Circuit with a capacitor:
V = E0Sint
i = E0/(1/C) [ Sin(t+/2) ]
Xc = 1/C is capacitive Reactance.
i = i0Sin(t + /2)
AC Circuit with an inductor:
V = E0Sint
i = i0Sin(t - /2) {Voltage Leading}
XL = L Inductive Reactance.
LCR Circuit (Inductor,capacitor,Resistor Circuit in series):
Impedance , Z = (L - 1/C)2 + R2
The above Expressino can be very well be given as:
Z = (XL-XC)2 + R2
For Phase angle ,
Tan = XL-XC/R
Resonance:
L = 1/C
The Impedance of the circuit is equal to R only.
0 = 1/LC
f0 = 1/2LC (Resonance Frequency)
Power:
Average Power ,
Pavg = Erms.Irms.Cos
Pavg = 1/2*E0I0Cos
Where Cos is the power factor.
Cos = R/Z
Choke Coil:
A Coil with low resistance and high inductance used to reduce current in AC Circuit without much heat loss is
called as a Choke Coil.
Power factor , Cos = R / (L - 1/C)2 + R2
R is Low and L is High thus is Reducing current.
Hope you all find it useful.
I have typed this whole thing the third time as before this two times I by mistake pressed (ctrl+w) , Press it
and you will find it out what happens.
plZ rate me if useful.
Cheers!!!!!!!!!!!!@@@@@@!!!!!!!!!!!
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