Inductor
What is inductance?Previously, we discussed that when charges flow through a wire a magnetic field is induced. And when there is a magnetic field, flowing charges are affected by it. Michael Faraday first noted this relationship.
He noted that a voltage or current is induced at the terminals of the coil that is opposite to that of the original current.
What do you mean a voltage or current is induced at the terminals of the coil? Do you mean voltage drop like that of a resistor?
No. Not a voltage drop as in a resistor. Although, the coil will have small voltage drop as any other conductor of current.
Faraday observed that:
This property of inducing an opposite voltage across the coil terminal is referred to as self inductance or inductance in general.
You stated that changing magnetic field generates current in the coil. Also, changing current or ac current passing through a wire creates changing magnetic field. How do both field interact? Does a greater magnetic field created?
I can't fully answer these questions yet. But what I can say is this much:
Let the changing magnetic field created by the changing current be quantified by the flux lines across a given area and denoted as df/dt. Flux lines are indicative of the magnetic strength of the field.
Then, the changing current or (changing?) voltage induced across the terminals due to changing magnetic field is equal to v= df/dt.
What if there is n number of turns?
For n number of turns the voltage at the terminals equal to
V=v1 + v2 + v3+…+Vn
V=n df/dt
How is current through the coil and voltage induced across the terminal of the coil are related?
As noted by Faraday, the changing magnetic field is proportional to the changing current in the coil.
df/dt a di/dt
From the above question we note that
V=n df/dt
Then, the following equation directly equates the induced voltage across the coil terminals and the di/dt.
V=L di/dt
In the above equation, L is the constant called inductance.
Because the relationship is directly proportional you have equated the voltage across the coil terminals and the di/dt using the constant L. How do you calculate the L?
I do not want to get into that discussion, and that is a topic for field theory.
The number of turns, the permeability of the core, the cross sectional area of the core, and the length of the coil are all factors determining the L.
What are the typical values of L?
The self inductance equation is important in electronics.
V=L di/dt
The self inductance is measured in Henrys. The typical values range from 1micro Henry to 10 Henry.
What does one Henry imply in terms of voltage generated across the terminals?
One volt is induced across the terminals of the coiled wire or the inductor if
So inductor is just a coil of wire wrapped around a core?
Yes. Usually wrapped around a core.
What will happen if the current is suddenly stopped and terminals get disconnected, will the magnetic field be maintained?
First of all the current cannot change instantaneously in the inductor. Note the equation, if the current changes instantaneously or at infinitely small amount of time it will cause infinite voltage which is impossible. I take "suddenly" to mean a speedy but gradual termination of current.
The magnetic field will not be maintained. The magnetic field will collapse. As it collapse, the changing magnetic field will create a current. But this time in the direction of the original current. Thus, the inductor will seek to maintain the original current flow (so to speak) for the first few moments.
What does an inductor physically look like?
Inductors are manufactured in various forms ans sizes. One typical form is shown below. Inductors also come in shape similar to resitors and have their own colour code. For inductor colour code visit: http://www.elexp.com/t_induct.htm.
(Source: www.ebacal.com/htm/ north-intro.html )
Are inductors produced in all values
No. You can combine inductors in parallel and series in such a manner that you can effectively have any value.
What is the resultant inductance value when you place inductors in series?
The inductors in series are similar to resistors in series.
The resultant value can be found as: Lt=L1 + L2 + L3
What is the resultant inductance value when you place inductors in parallel?
The inductors in parallel are similar to resistors in parallel.
The resultant value can be found as: 1/Lt = 1/L1 + 1/L02 + 1/L3
Where can I find more information about inductors?