Inductors
Inductance : An inductance is the element in which energy is stored in the form of electromagnetic field.
*The Inductance is denoted by `L`
*The Inductance is measured in Henry.
For an inductance the voltage across it is proportional to the rate of change of current passing through it.
V (t) α di(t)/dt
V(t) = L *di(t)/dt
Where L= Inductance or proportionality constant
The symbol of inductor is given below :
If the voltage is known across the inductor the current si given by
I(t) = 1/L*∫ v(t) dt
The power of the inductor is given by
P (t) = v (t)*I(t)
The energy stored in inductor is in the form of an electromagnetic field
W = ½*Li(t)^2
The inductor connected in series
The inductor connected in parallel
The phenomenon of inductance is of two types
1. self inductance
2. mutual inductance
1. self inductance : The inductance which produce the magnetic field or the concept of inductance by its own is known as self inductance.
L = (Nφ)/I
L = (N^2* μ*A)/l
Where N = no of turns
μ=permeability of the material
A = area of the conductor
l= length of the conductor
Concept of self inductance :
It is the property of the coil due to which it opposes the change of current flowing through itself is called self inductance of the coil.
EMF: Emf is abbrivated as electro motive force i.e. the force rises due to the motion of electrons. Emf is of two types
EMF: Emf is abbrivated as electro motive force i.e. the force rises due to the motion of electrons. Emf is of two types
1. Dynamically induced emf
2. Statically induced emf
The inductor is a current dependent element. If the current in the coil increases, the self induced emf of the coil in opposite direction increases and vice-versa.
* The greater the self induced emf the greater the self inductance of the coil and hence larger is the opposition to the change in current.
Expression for self induced emf :
We know that L = (Nφ)/I
LI = Nφ
Apply differentiation on both sides
-d(LI)/dt = -d(Nφ)/dt
-L dI/dt = -N dφ/dt
We know -N dφ/dt = e ( induced emf)
-L dI/dt = e
L = -e/dI/dt
Mutual inductance: The property of one coil due to which it opposes the change of current in the neighboring coil is called mutual inductance between two coils.
Expression for mutual inductance:
Co- efficient of mutual inductances is defined as weber turns
in one coil due to 1amp current in the other.
Let there are be two magnetically coupled coils having N1 & N2 turns respectively.
* A current flowing in first coil produces flux φ1 webers in it . If the flux links with the turns of second coils then the flux linkages in the second coil for unit current in the first coil is
M = (N2*φ1)/i1
But φ2 α φ1 (or)
Φ1 = k*φ2
Where k= Co-efficient of coupling.
If k= 1 then φ1 = φ2
M = (N2*φ2)/i1
Inductance working:
Inductance working:
Inductors
Inductors are also used in electronic circuits. There are two types of inductors which are in use:
1. Radio frequency coils (or) inductor
a. single layer solenoids
b. wave wound coils
2. Audio frequency coils and inductors
a. Low frequency transformers
b. High frequency transformers (or) Radio frequency transformers.
1. Radio frequency coils:
These coils are of inductance between 100mH to 1H and used in radio frequency circuits of a radio, T.V. receivers
a. single layer solenoids :
The wire is usually is 16 (or) 18 guage. The losses are kept minimum by avoiding insulating material. The indcutive reactance “2∏fL” depends upon the frequency “ f”
b. Wave wound coils:
The capacitance is kept minimum at the turns of the conductor which exists at the turns of inductor. The capacitance is avoided by making the coils so wound. There are several methods used most commonly used method is “wave winding”.
2. Audio frequency coils:
These inductors are used I circuits with currents of low frequency stages as audio frequency choke transformers . Their inductances is usually of the order of 3Henry.
a. Low frequency transformers:
These transformers are used in circuits with currents of low frequency at input and output . The low frequency input transformers are used for coupling microphones with firs amplifier stage. Primary winding matches the microphone impedance, secondary winding equals the input impedance values. The output low frequency transformers are employed in the output stages of radios,T.V. etc. primary winding is anode whereas the secondary winding is connected to the loudspeaker.
b. High frequency transformers:
In every radio, radio frequency signals are converted into intermediate frequency signals. Intermediate frequency transformers are used for coupling such signals from one stage to second stage. They are of two types
a. variable inductance Intermediate frequency transformers. The inductance varied by an iron core.
b. variable capacitance Intermediate frequency transformers. These are variable type capacitors. Capacitance is varied to tune the frequency`s to the desired intermediate frequency.
Inductor in electronics :
Inductor in electronics :
No comments:
Post a Comment