Induction Experiments

Concept: Induction Experiments

Video Transcript

Hey guys, in this video we're going to begin our discussion on electromagnetic induction with just talking about, what it is, okay? What the phenomenon of electromagnetic induction is. Alright, let's get to it. Now, we know, we've seen this before, that if we have some coil of wire and we complete a circuit with some potential source, potential different source, a voltage source, which we put a voltage across this coil, will produce some sort of current in it, okay? It doesn't have to be a coil, it could be a square or rectangular circuit as we've seen before, but any conducting wire, if you put a voltage across the two ends of it, you'll introduce a current in that wire, okay? Well, it turns out, this wire doesn't actually have to be connected to a voltage source, in order to produce a current on it, a voltage could be what we would call induced, okay? Now, common ways to induce a voltage on a coil of wire include moving a bar magnet in and out of this coil of wire, so you're moving this bar magnet in and out. When the bar magnets have rest, there's no induced voltage on the coil, but when the bar magnet is moving either towards the center or away from the center, then there is an induced voltage. Another thing to do is vary the current in an electromagnet, a very common example of an electromagnet is a solenoid, that's what I've used, okay? I can draw a little arrow through this voltage source, through this battery, that arrow means variable, as I vary the voltage supplied to the solenoid, I vary the current in the solenoid, the larger the voltage, the larger the current; the larger the current on the solenoid, the larger the magnetic field, okay? So, as I vary this current, the magnetic field produced by the electromagnet varies and a current will be produced in this coil. Lastly, I can use this switch here, in the circuit, to turn the electromagnet on and off, off when the circuit is broken, on when it's complete off on, off on, okay? By rapidly turning it on and off it's very similar to changing the current, when it's on, there's a current going through it, when it's off, there's no current, and this will also induce a voltage on the coil of wire, okay? This induced voltage is always called an induced EMF, okay? Remember guys, that EMF or electro-motive force is just another word for voltage, okay? But everyone calls it an induced EMF, and this leads to an induced current, okay? If you ever have a wire, right? Just some arbitrary wire, point A point B, and you have a voltage across those two points, you are going to produce a current in that wire, okay? I have myself there, this is the figure I just drew, this is assuming point B is at a lower potential than point A, okay? This process of inducing a voltage on something, which then induces a current is known as electromagnetic induction, and this is the phenomenon that we're going to be studying in this chapter, okay? These three images right here, are a common example of current induction; when I bring the bar magnet towards the loop, there is a current induced in this coil; when the bar magnet is at rest relative to the coil, there is no current, and then when I'm pulling the bar magnet away, there's also a current induced in this coil, okay? This is a very, very common example of current induction via the process of electromagnetic induction, okay? Now, lastly, the magnitude of the induced current depends upon how rapidly you're changing the system, certain types of changes like we said, moving the bar magnet in and out of the coil, varying the current in an electromagnet near a coil, turning an electromagnet on and off, those certain types of changes will induce a current, and the magnitude of that current, that induced current, depends on the rates of these changes; for example, if you're moving a bar magnet into a coil, the faster it goes the larger the induced current, if you're changing the current in an electromagnet, the faster the current changes the larger the induced current, okay? This completes our introduction to the phenomenon that is electromagnetic induction, later we're going to continue along this and talk about the actual physics that goes into this. Alright guys? Thanks for watching.