Welcome to another Unisur physics podcast. Today we'll be using two demonstrations to visualize the geometry of the magnetic field surrounding two different magnets. Let's first take a quick look at the construction of the 3D magnetic field demonstrator. As you can see it has six acrylic panels which are covered in little compass needles, about 45 per panel. So we have around 270 little compasses attached to the field demonstrator. Now if we look at a bar magnet, this is a cylindrical bar magnet. You don't see too much, it's got a North and a South Pole, but you don't see the magnetic field at all. But if you bring it up near the magnetic field demonstrator you'll see that the little compass needles align themselves with the magnetic field lines. So let's see what the magnetic field lines look like around the whole bar magnet. Now the field demonstrator has a removable panel. You insert the bar magnet, slide the panel back in again and there we have it. The invisible is revealed. So each of the little compass needles are aligning themselves with the magnetic field that surrounds the bar magnet. Now the convention scientists use to draw magnetic fields is that the magnetic field lines come out of a North Pole and loop around into a South Pole. Okay, well let's have a look at another magnet shape. Here is a horseshoe magnet. It has a South Pole and a North Pole just like the bar magnet did. Actually you could think of the horseshoe magnet as a bar magnet that's been bent around in the shape of a horseshoe. But the big question is what will the magnetic field lines look like? Okay well while we set up the demonstration have a little think about what they might actually look like. Okay here's the magnetic field demonstrator and we can insert the horseshoe magnet into the side and slide the panel in. We give a little tap just to get the compass needles aligned and there we have it. Now let's have a close look at what we're seeing here. We'll see that the compass needles round the back of the field demonstrator haven't strongly aligned with each other. If you get a little tap they do line up so it probably indicates that the magnetic field round this area is a little weaker. What's quite interesting if you look and on at the horseshoe magnet it gives a very similar pattern to what we saw with the bar magnet with the field lines coming out of the North into the South in that very distinctive shape. And if we look towards the center of the two poles between the North and the South pole we'll see that the field lines go from the North down into the South. Okay I hope you enjoyed the two 3D magnetic field demonstrations and I look forward to sharing some more physics with you in another UNICEAR VODCAST.