The magnet moves as shown magnetism moves. This is a fun and accessible way to understand how magnetic fields work. By moving a magnet close to a metal surface or another magnet, a force is created.
Magnetic fields are described by equations that show how the strength and direction of the magnetic force changes with location. These equations are dependent on how the magnet is oriented.
You can experiment with this yourself using simple supplies. You will need: A needle, thread, iron filings, and a bar or rod of iron or steel. You can also use a fridge or freezer for the ice to set the filings in place.
To see how magnets move, lay out the filings on a flat surface and place the bar or rod of iron or steel on top of the filings.
Always in the same direction
The magnet always moves in the same direction as shown by the arrow. This is important to note because it means that the magnet will always pull towards the south pole of the Earth.
The strength of the magnet does not matter, it will always move in this way. The only thing that changes is how far it moves in response to the surrounding magnetic field of the Earth.
A weaker magnetic field will result in a weaker response from the magnet. A stronger magnetic field will result in a stronger response from the magnet. This is what allows us to identify what side of a bar of metal is which – if it is placed on one side of the ocean, it will move in one direction, and if it is placed on the other side, it will move in another direction.
We also mention that you can easily tell which side of a bar of metal is which because they are not symmetrical – one side is different than the other due to how it responds to the Earth’s magnetic field.
The coil moves in a circle
In this example, the coil that is attached to the magnet moves in a circle. As the coil moves, the magnetic field of the magnet through the coil changes.
This is similar to how a fan moves air. As the fan blade moves, the air that hits it changes direction and speed.
This example shows how a motor works-the magnet inside of the motor is fixed, and the coil that is attached to it moves in a circle. This causes the magnetic field of the magnet through the coil to change, which then generates electricity.
A motor can have one or many coils attached to it depending on its function. For example, an oven has one large coil inside of it whereas a fan has many small coils within it.
The coil moves back and forth
In this experiment, the coil moves as shown in the video. A magnet is placed next to the coil and as the coil moves, the magnet moves as well.
The magnet does not move independently of the coil. The magnet only appears to move independently because the coil moves and the magnet is placed next to the coil.
This is an important distinction to make when exploring magnetic fields. It is easy to think that things like iron filings or a moving car are moving due to a magnetic field, but in reality, they are only moving because something else moved first.
More specifically, they are only moving because of a preceding motion caused by something else. This isn’t the case with a magnetic field due to a simple fact: there is no “something else” that causes movement except for whatever material being studied in an experiment.
Understanding how a magnet works
Magnets have a north and south pole, just like the Earth. A magnet will always attract to a magnet of the same size, and opposite polarity.
When a magnet is placed over a coil of wire, the magnetic field that is emitted by the magnet interacts with the wire. The wire moves as shown in the video above, demonstrating how the magnet moves as well.
The strength of the magnetic field emitted by the magnet determines how much force is exerted on the wire. The more powerful magnets require more thick wires to exert movement on the device.
The way we design our devices depends heavily on how magnets interact with them. Devices such as phones have anti-drop features due to strong magnets placed inside of them. Other devices rely on magnetic forces for function, such as fridges that keep things cool with a magnetic layer.
Understanding how a coil works
Now that you know how a magnet moves a coil, let’s look at how a coil moves a magnet.
A coil is made up of many turns of wire. When the current flows through the wire, it produces a magnetic field. The more turns of wire, the stronger the magnetic field.
When the current changes direction, so does the magnetic field. This is called phase shifting and is what allows a computer to determine which way your device is pointing.
When there is no current flowing through the coil, there is no magnetic field. This allows for very precise movements depending on what your device does.
There are several different types of coils that function differently depending on what they are made of and how many turns of wire they have. These all have different functions within devices.
Moving the magnet closer to the coil increases the intensity of the magnetic field
By moving the magnet closer to the coil, you increase the strength of the magnetic field that the coil is in. This is because you are adding more of the magnetic field to the coil.
By moving the magnet away from the coil, you decrease the intensity of the magnetic field that the coil is in. This is because you are taking some of the magnetic field away from the coil.
The more turns in your coil, the greater strength of magnetic field your coil will hold. This is because there is more wire and more opportunity for a stronger force between wires.
The stronger your magnet, the higher intensity of magnetic field your coil will hold. This is because there is more strength of magnetism, thus more strength of influence on other objects.
The current passing through the coil creates a counter-field that repels the first field
Now, let’s talk about what’s actually happening when you move the magnet and the coil. As we’ve discussed, when you move the magnet, the electron spins in the atom cores shift due to the imposed external magnetic field.
But how does this translate to movement?
As we know, atoms are highly compacted and have nuclear spins that respond to external magnetic fields. When you introduce movement to the atom cores, they respond by shifting their internal spin in response to the external magnetic field.
What happens when you introduce an external force on something? It moves! That is what happens here as well. The electron spin in the atom core moves in response to the external magnetic field and thus causes movement of the atom core itself.
Move the magnet slowly to create smooth motion
To create smooth motion with your DIY robot, you will need to move the magnet slowly across the ferrous plate. The speed at which you move the magnet across the plate will determine the speed of your robot.
A good tip is to use a stopwatch to time how long it takes your magnet to traverse the plate once. Then, divide that time by two and that is how long it should take for your magnet to move back and forth across the plate.
This way, your robot will have consistent timing between movements. It will not be too fast or too slow!
Some people use wheels instead of a flat surface for their robots. If you do this, make sure your bot has stability so it does not tip over or travel in an uneven manner.