An Inductor And Different Types

Inductance   is a   property  in an electronic circuit where a change in current in  a   circuit   creates a voltage in the  circuit itself and also the  nearby   circuits.  A  steady stream of  current in a conductor creates  a   magnetic field  around  the conductor. A  varying magnetic field  in  a   circuit  induces a  voltage in an adjacent conductor. An inductor is    a  passive electrical  component that stores energy in its magnetic     field.  Inductance is  created from the magnetic field that is formed    around a  conductor which  carries current that tends to oppose the change in current.

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Inductor Property

All conductors have inductance and can be made  into an inductor. A   length   of conductor can become an inductor and the  inductance will   be  greater  when it is wound into a coil. An inductor is  usually a    conductor turned  into a coil form, which concentrates or  increases   the  magnetic field  of the conductor.   An  electric current   through a inductor creates a magnetic flux or    magnetic field. A change  in the electric current also creates a    change  in the magnetic flux  which is proportional to the current.

Self Inductance

A     conductor has self inductance where a  change in the electric   current    through a circuit having inductance induces a proportional    voltage  that  opposes the change in  current. A varying magnetic field   in the  coil is  needed for inducing an opposing voltage  in the coil.   The  changing magnetic flux  generates an electromotive  force that   opposes  the change in current. This changing magnetic flux  induces a   voltage in  the coil. This voltage tend to oppose the change  and will    try to  decrease the current if it is increasing or increase  the   current  if it  is decreasing. This opposing flow of electric current is termed  as  self induction. Self inductance can be illustrated using an experiment. Here a battery is connected through a switch across a coil wound many times on an iron     core. A small lamp that lights on battery voltage is connected  across    the terminals of the  coil. An ammeter is connected in series to     the coil and the switch. When the switch is opened, the ammeter    reading  falls to zero but the lamp flashes very brightly and goes out.

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Mutual Inductance

Mutual     inductance happen when the coils are kept near so that the magnetic     flux from one inductor cross to the other and thus they exhibit  mutual    inductance. It is the phenomenon of production of induced  current in   one  coil by changing the magnetic flux due to current in  another coil.    The varying current in  the coil or circuit induces a voltage in an    adjacent coil or circuit  is called as mutual inductance. Mutual    inductance between coils  depends upon their coefficient of coupling,    which can vary from 0 to  1.

Factors Affecting Inductance

The inductance of an inductor depends on

1. The number of loops of the coil. The larger the number of turns the greater is the inductance.

2. The size of each loop. The greater the size of the loop, the greater is the inductance.

3. The permeability of the material used as the former to wind the  coil. The magnetic flux can be increased by coiling the conductor  around a    material with high permeability. Materials with high  permeability    includes soft iron, ferrite, etc.

4. Cross section of the core. The larger the cross section of the core, the higher the inductance.

5. Spacing of the turns. The smaller the spacing between the turns of the coil the greater is the inductance.

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The unit of measurement of inductance is the henry and the symbol for inductance is L 

An inductor of 1 henry of inductance produces an EMF of 1 volt when the current through the inductor changes at the rate of 1 ampere per second. Henry is a large unit and smaller units are usually used in    practice  especially in radio, where millihendry mH or microhenry microH are used.

The relationship between self inductance L, voltage, and current in a circuit is

V = L * di/dt

Where     V is the voltage in volts, L is the self inductance, i is the  current    in amperes,  and t is the time.  The voltage across the  inductor is    proportional to the product of its inductance and the  time rate of    change of the current through it.

Inductance     is present in almost all circuits which may have beneficial or     detrimental effects to the function of the circuit.  Inductors can be     used where the current and voltage changes with time. Inductors have    the  ability to  delay and shape alternating currents. Common   inductors   consists of a specific number of turns of enamelled copper wire, wound around  a  former such as air, iron, laminated steel, ferrite, Teflon etc.

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An   ideal inductance has inductance but no resistance or capacitance and   does not dissipate or radiate energy. However real inductance have     resistances due to the resistance of the wire and the parasitic     capacitances due to electric field between the turns of the coil    having slightly different potentials. Energy is dissipated by the    resistance of the wire and by the losses of the magnetic core due to    hysteresis. 

Uses and Effects of Inductance

Inductances   are widely used in radio circuits, other analog circuits, and signal   processing. Inductances provide frequency selection in a tuned circuit   of the radio. Large inductors are used in power supplies to filter out   mains hum, power supply noises, and   fluctuations in the DC. Inductors are used in  filter  circuits  to   filter out waveforms or in energy storage systems. Audio  chokes have   many turns of wire on iron core, which has inductances of 1  to 100  henrys.   Radio frequency chokes  have inductances of a few turns of  wire wound  on  a nonmagnetic core. Power transformers are used in power  supplies  for most electronic equipments. Coupled magnetic fluxes  between a  stationary and a rotating inductor coil is used to   produce mechanical torque in induction motors. Inductors are used as  an  energy storage device in switch-mode power supplies. Variable  inductors  use an adjustable core, which is  usually a ferrite  core or  powdered  iron core, that can change the  inductance.

Inductances    are found in transmission cables that   determine the characteristic    impedance in a cable. Inductances are  also  seen in microphone and    computer network cables that use special  cables  to reduce it. Long    power transmission lines also shows  inductances which  limits the AC    power that can be sent through them.

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Types of Inductances

There are 2 types of inductors, fixed inductor and the variable inductor.

Fixed   inductors are air core inductor, radio frequency inductor,   ferromagnetic core inductor, laminated core inductor, ferrite-core   inductor, and toroidal core inductor.

Variable   inductors are  widely used in radio applications to set a definite   oscillating frequency and to tune the resonant circuits. These may   include many different types of slug tuned inductors. Slug tuned   inductors are widely used in RF and IF stages of super heterodyne radio receivers. Tuned inductors are also used as the tank coil in the final RF power amplifiers.