Welcome to my first video about inductors.
So, what is an inductor?
Generally speaking an inductor is a device that temporarily stores energy in the form of a magnetic field. Inductors are usually just coils of wire and one of the basic properties of electromagnetism is that when you have current flowing through a wire, you will create a small magnetic field around it. So if you coil up a lot of wire you'll get a stronger magnetic field.
When current first starts to flow through the coil, the magnetic field starts to expand... then stabilizes...and then you've got some energy stored in the magnetic field. When current stops flowing, the magnetic field starts to collapse and the magnetic energy gets turned back into electrical energy.
So they're kind of like a temporary storage area for energy.
Capacitors store energy in the form of a static charge and resist sudden changes in voltage. well, Inductors are very similar... they store energy in the form of a magnetic field and resist sudden changes in current.And if you only learn one thing from this video remember, "the current in an inductor cannot instantly change." It always lags by certain amount of time.
Now let me give you an example.
Normally when you connect a voltage source to a load resistor the current will be given by ohms law. In this case 10 volts divided by 20 ohms gives you 0.5 amperes. And for this demo I'm going to be using a 50% duty cycle square wave.
So half the time you'll get 0.5 amperes flowing and half the time there will be no current flowing.
Okay so here's the 1kHz input square wave.
And here's the current waveform... also perfectly square.
Now watch what happens when I add a 5 milli henry inductor in series with the circuit.
All of a sudden the square wave isn't so square anymore. There's a little bit of lag in the current.This is because it takes a certain amount of time to store and release the energy in an inductor.Now let's try that again with a higher input frequency of 10kHz.Now it's even more obvious that the inductor is impeding the sudden changes in current.
This happens more and more as I raise the frequency of the input wave.
At 100kHz there is no square wave anymore. It takes a longer time to store and release the energy in the inductor than the time it takes for the input wave to switch from high to low. So in this situation the inductor is starting to average out the current over time.
This is very useful. It forms the basis of LC low-pass filters which I will cover in another video. A quick example: If I add a 1000 microfarad capacitor after the inductor here I get a very clean D.C. output from a square wave input. And this is what good power supplies use to smooth out voltage.
To prove to you that all this happens because of expanding and collapsing magnetic fields I'm going to feed a square wave into this unshielded inductor.And I'm going to use another inductor as a magnetic probe.So I can view any magnetic field changes on the oscilloscope.On top I have the input wave and on the bottom you can see the magnetic field that I'm picking up as I get closer to the inductor.
Finally, inductors have almost no effect on D.C. They're basically just pieces of wire with a resistance of a few Milli ohms.Alright that's the basics of how an inductor works. Now I've got a few more videos with more information on them and some practical examples.