Magnetism: The One Thing You Need to Know
Do you work with magnets and sensors? You need to know this one idea.
Moving electrical charges push and pull on other moving electrical charges.
Magnetism is the description of how this happens.
This one idea explains how everything from electrical generators to motors to permanent magnets work. If you understand this one idea, you will be able to understand much about how magnets and magnetic sensors operate.
Here is the road map for this article:
- Groups of moving charges are common.
- Groups of moving charges push and pull on each other. Why? It's the way the world works.
- We explain this using the idea of magnetic fields. A group of moving charges creates a magnetic field.
- Magnetic fields push and pull on moving charges.
- Motors, generators, magnets, and magnetic sensors all can be explained using this one idea.
Electricity
Electrons in Atoms
Groups of moving charges
There are two common groups of moving electrical charges. These both have an effect on our everyday lives.
- Electricity
- Atoms inside solid objects
Electricity is the movement of charges inside wires. An electrical generator or a battery causes charges to move through wires. Just think of electricity as a long line of charges moving through a wire. The actual details are more complex, but this is good enough for now.
Atoms consist of a positively charged nucleus and negatively charged electrons. In solid objects, the nuclei are in stable positions while the electrons move. These moving electrons are in all solid objects. This movement is complex. It is different in different types of materials. This is why different materials are different from each other. For now, just think of the electrons as moving around in complicated patterns inside of an object.
A Real World Example of Magnetism: 2 Wires Pushing and Pulling on Each Other
If you put two electrical wires parallel and close to each other, they will either push away or pull toward each other. You can do this as an experiment if you use very fine gauge wire with a small battery. (Don't do it too long or the wire can become very hot! Don't do it too long or you'll run down the battery very quickly.) Most common gauge wires are too stiff to see much movement. The push or pull is determined by whether the electricity is flowing the same direction or not. Don't worry about the details. The important thing is knowing that the electrical charges moving in one wire affect the moving charges in the other wire.
What happens if electricity is moving in one wire but not the other? Nothing. The wires wouldn't affect each other then. This is the basic fact of magnetism. One group of moving charges affects another group of moving charges.
Magnetic Fields
Obviously, the two wires are not touching each other. How do the two wires affect each other? Movement of charges creates a field around the charges. When electricity flows through one wire, a magnetic field forms around the wire. What is a magnetic field? You can think of it as a region of influence around the charges. This region affects other moving charges.
The more charges and the faster they move, the stronger the field is. The closer something is to the wire, the stronger the field is. When charges are not moving, there is no field. When far away from the charges, the field is very weak. The manner in which charges form a field or interact with a field is complex. The fields, motions, and directions of things work at a system of right angles to each other.
Sources of Magnetic Fields
Any group of moving charges creates a magnetic field. Two common sources of magnetic fields are electricity in wires and magnets. Electricity moving in wires creates a magnetic field (as mentioned above). The electrons moving inside of a permanent magnet create a magnetic field.
The movement of electrons inside any object creates a small magnetic field near the electron. In most objects, these fields are pointing in many different directions and just cancel each other out. However, in some special objects, these fields point in the same direction and add together. When the all of these fields add together, the result is a large field that extends outside of the object. This is what a permanent magnet is. The electrons inside a permanent magnet move in organized (and complicated) patterns that create fields that add together to form a very large field.
For now, you can just think of a permanent magnet as having a huge number of electrons moving in unison to create a large magnetic field. Another article will talk about this in more detail.
Magnetic Fields Push Moving Charges
Magnetic fields push or pull on moving charges. The details of how hard and in what direction are complicated. For now, it's enough to know that the magnetic field pushes on moving charges. This is why two parallel wires with electricity push or pull on each other. This is why magnets attract or repel each other. This is why magnets can attract certain types of materials. This is how electrical motors and generators work.
Recall that permanent magnets have moving electrons inside of them. When you bring two magnets (call them A and B) close together, they each enter the other's magnetic field. The electrons inside A produce a field. The electrons inside B produce a field. When B enters the field from A, the electrons moving inside B are pushed or pulled by the field from A. When A enters the field from B, the electrons moving inside A are pushed or pulled by the field from B. This is why you can feel magnets attract or repel each other.
As you may have guessed, electrical wires and magnets can affect each other. This is how generators and motors work.
Comments
Please note that this article is simple and descriptive. The purpose is to help you gain an intuitive understanding of what is happening inside of magnets and sensors. If you want to learn about the details, there is no escaping the use of mathematics and physics.