Transcription
[Music] hi and welcome back to the three sighs lessons code UK. By the end of this video, you should be able to describe the forces produced when magnets are brought together. You should then be able to describe the difference between permanent and induced magnetic.
A bar magnet, and you may have seen one of these at school. As you can see, the bar magnet has two ends, and we call these the poles. So we've got a North Pole and a South Pole. Now, a key point is that the magnetic forces are strongest at the poles of a magnet, and we'll be looking at that again in the next video when we look at magnetic fields.
Okay, now when we bring two magnets close together, then they exert a force on each other, and I'm showing you that here. Two like poles repel each other, and we're seeing that on this picture. So as you can see on the left-hand side, we've got two North Poles close together, and on the right-hand side, we've got two South Poles close together. In both these cases, there's a force of repulsion, and that repulsion is forcing the magnets apart.
Two unlike poles attract each other, and we can see that here. On the left-hand side, we've got a North Pole and a South Pole attracting each other, and on the right-hand side, we also have a North Pole and a South Pole attracting each other. The attraction and repulsion between two magnetic poles are both examples of non-contact forces, and that's because the magnets don't have to touch to experience the force.
Okay, we're going to look now at permanent magnets and induced magnets. A permanent magnet produces its own magnetic field, and a good example is the bar magnet that we saw earlier. If we bring a permanent magnet close to another permanent magnet, then they can attract or repel each other depending on the direction.
Now, an induced magnet is an object that becomes a magnet when it's placed in a magnetic field. So I'm showing you here two objects, and neither of these are magnetic. We've now placed a permanent magnet between them. As you can see, there's a magnetic field, and the permanent magnet, the magnetic field has caused the two objects to become magnets. So these are now induced magnets.
Now, the key fact is that induced magnetism always causes a force of attraction. And if we take away the permanent magnet, then the induced magnets lose most or all of their magnetism quickly. Remember, you'll find plenty of questions on permanent and induced magnetic in my revision workbook, and you can get it by clicking on the link above.
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