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The foundation of modern electrical engineering was the discovery by Faraday that when the magnetic flux through a loop of wire was varied, a voltage was set up in the wire. This process is called electromagnetic induction.

  • A conductor wound in the form of a coil is called an inductor (or solenoid)
  • An inductor has a strong magnetic field that has many uses
  • Inductance opposes current change
  • An inductor may have its inductance increased by:-
    • adding more turns
    • introducing an iron core through the centre of the turns

Inductance[edit | edit source]

Inductance is the property by which it opposes the change in current through a circuit.

L = Inductance in Henry N = Number of turns in wire coil A = Area of coil in square ² meter l = Average length of coil in meters

Magnetic of Inductance[edit | edit source]

L = Inductor in Henrys

Magnetic of Turns[edit | edit source]

Φ = N B A

A-area of cross section of the coil

Voltage of Coil's Inductance[edit | edit source]

= -ξ

Voltage of Coil's Turns[edit | edit source]

Reactance[edit | edit source]

Impedance[edit | edit source]

Phase Angle[edit | edit source]

For an inductor without resistance, the voltage and current is out of phase by 90o (π/2 radians).

For an inductor with resistance, the voltage and current is out of phase by θ:

Tan θ = = 2πf L/RL

When there is a change of angle, the frequency also changes. This can be used to shift the frequency:

f = ( 2π / Tanθ ) ( RL / L )

As frequency is one over time:

t = ( Tanθ / 2π ) (L / RL )

Frequency Response[edit | edit source]

, Shorted Circuit. I = 0
, Opened Circuit. I ‡ 0
, Shorted Circuit. I = V / 2 RL

I - can be drawn, at certain frequency the value of current does not change with. So this circuit can be used as a high pass filter.