Familiarisation with Inductor 
Theory
Function of an Inductor
The function of a valve is to control the amount of fluid that flows through a pipe.
Figure: 1
In an electronic circuit, the resistor is used to control the amount of current that flows through a conductor.
Figure: 2
Mother device that controls the current is the inductor .
Figure: 3
However unlike the resistor that affects the current uniformly at all times, the inductor only affects currents when thy are changing in value.
Similarity with Capacitor
- Rate of change of voltage in a capacitor depends upon the current through it
- Rate of change of current in an inductor depends upon the voltage applied across it.
- Like capacitive current , inductive current is not simply proportional to voltage
- Unlike the situation in a resistor, the power associated with inductive current (V times I) is not turned into heat but is stored as energy in the inductor’s magnetic field.
Equation of an Inductor
$$V= L\frac{dl}{dt}$$
- L is the inductance and is measured in henry.
- Putting a voltage across an inductor causes the current to rise as a ramp
- 1 volt across 1 henry produces a current that increases at 1 amp per second
Structure of an Inductor
Figure: 4
It consists of a wire wound as a coil around a core. The core may consist of a air filled hollow tube or solid material.
Inductance
The amount of inductance in henries a coil has, is determined by the following factors -
- No of turns of wire wound around the coil
- Cross sectional area of the coil
- The material type of the coil
- The Length of the coil
Figure: 5
Test Question
If the number of turns of coil around an inductor is increased ( doubles ), how will the inductance change ?
Figure: 6
- Increase
- Decrease
- Will Not Change
If the distance between the turns of coil around an inductor is increased ( doubles ), how will the inductance change ?
Figure: 6
- Increase
- Decrease
- Will Not Change
If the diameter of the coil around an inductor is increased(doubles),how will the inductance change?
Figure: 7
- Increase
- Decrease
- Will Not Change
Inductive Kick
An Inductive is capable of producing a momentary voltage that is much higher than the voltage of th power source that supplied the current to create its magnetic field . This temporary voltage is called an inductive kick.
Figure: 8
Example of applications of inductive devices to provide an inductive kick is a Combustion Engine ignition system that creates the spark across the gap of the spark plug.
Slides: Familiarisation with Inductor