In this video, we're going to look at the generator effect, which is also known as electromagnetic induction. To do this, let's imagine we have two magnets with a magnetic field between them. If we now take a piece of wire that's been bent into a coil shape and move it through the magnetic field, it will induce a potential difference in the wire, which you can see by the plus and minus signs. There are a couple of important things to notice here, though. One is that whenever the wire stops moving, like it does whenever it reaches the top or the bottom, then the potential difference disappears. This is because it's the change in the magnetic field that the wire experiences as it moves through it that creates the potential difference. So if the wire is not moving, then there won't be any potential difference because nothing's changing. The other thing to notice is that the direction of the potential difference swaps each time we change the direction, which is why the plus and minus signs keep switching around. Now, at the moment, we just have a piece

of wire. We don't have an actual circuit, and so even though there's a potential difference, it can't generate any current. However, if we joined the two ends together so that we had a complete circuit, then the induced potential difference would generate a current because electrons would be able to flow around the circuit. The same thing happens if we keep the wire still and instead move the magnets up and down. This is because the wire is still experiencing a change in the magnetic field, which, remember, is the key idea in electromagnetic induction. If we instead move the wire back and forth like this, though, then this time there won't be any induced potential difference or current because the wire isn't actually experiencing a change in the magnetic field. Now, if we wanted to change the size of the induced potential difference and therefore the current that it generates, we can do three things. One is to change the strength of the magnetic field. For example, if we used stronger magnets which produced a stronger magnetic field, then would induce a larger potential

difference. The second is to move the wire or the magnets more quickly. The faster they move, the faster the magnetic field will change, and so the bigger the potential difference will be. The final change we can make is to shape the wire into a proper coil so that it has multiple turns. And the more turns it has, the bigger the induced potential difference will be. So to summarize everything up to this point, when a wire experiences a change in magnetic field, a potential difference will be induced across the wire. And if the ends of the wire are connected to make a closed circuit, then a current will flow around the circuit. In addition, we can increase the strength of the induced current by increasing the strength of the magnetic field, increasing the speed that the wires or magnets move at, or by adding more turns to our coil. The very last thing we discover is how this concept works when removing a single magnet into and out of a coil of wire. Just like before, this movement of the magnetic field relative to the coil induces a potential difference in the

coil and because the circuit's complete, this generates a current. Also, like before, whenever we change the direction of the magnet, it changes the direction of the current. And we can also change the direction of the current by swapping the poles of the magnets, like if we were to turn it around the other way. Anyway, that's everything for this video, so hope that all made sense and I'll see you again soon.

GCSE Physics - Generator Effect / Electromagnetic Induction #81

Hi - we make video lessons for GCSE science and maths. The lessons give a concise run through of everything you'll need to know for your exams.

Each video has been designed specifically for the 9-1 GCSE courses, and although they most closely mirror the AQA spec, everything you need to know for the main exam boards will be covered.

We also have a website where you can work through the lesson videos and answer a series of practice questions to check you know all the required learning points. All your progress is automatically tracked, and you can sign up at www.cognitoedu.org

Best wishes,

Amadeus & Tom