The terms magnetic field and electric field are often thrown around haphazardly. Usually without understanding exactly what the differences are between them. This is not surprising; magnetic fields and electric fields are complex phenomena that act similarly in some ways. Though this is true, they are not the same things and need to be understood separately, as well as how they work when combined.
Understanding Magnetic and Electric Fields
We use the magnetic field to describe the influence of magnetism on a point in space. There are some materials in our world, typically metals, that will attract or repel one another physically when you put them close together. Certain materials in physical magnets generate magnetic fields, while other materials remain unaffected by the phenomena. When magnets have no effect on a material, it is classified as non-magnetic. Examples of these are wood, plastic, paper, glass, and rubber.
Similarly, in electrical circuits, electric fields exist around electric objects. An electric field describes the influence of electricity on a point in space. Particles present in matter exhibit both attraction and repulsion among themselves, alongside particles that remain entirely unaffected. Insulators earn their name when charged particles have no effect, in contrast to conductors that respond to these particles.
Interactions and Characteristics
We often group Electricity and Magnetism together, because one can affect the other. However, some materials can conduct electricity but are not magnetic. Both are a result of charged particles in the atoms that make up matter. In a copper conductor, a stream of electrons moving constitutes an electric current. This current carries an electric field with it. It is an electric field, rather than a magnetic one, because the moving electrons interact with each other through the electric fields between them. Moving electrons generate a magnetic field around the conductor.
The copper conductor itself is not inherently magnetic. However, by passing an electric current through it, an electric field is generated within, and a magnetic field forms around it.
While conductive materials that aren’t magnetic are common, there are also magnetic materials that don’t conduct electricity. These are termed magnetic insulators. They possess a form of “magnetic order” allowing magnetic attraction but act as electrical insulators, preventing electric current flow.
A magnetic field is generated in materials that have a certain alignment or grouping of their intrinsic magnetic moments. These small “pockets” of alignment are called magnetic domains. When many of these domains align in the same direction, the material exhibits a magnetic field. It’s unrelated to the material’s ability to conduct electric current, as electrons may or may not flow through the material. Some materials can be “magnetized” by exposure to a magnetic field, causing the domains to align. Others remain non-magnetic regardless of exposure.
An electric field exhibits a potential difference or voltage across it, representing the force between opposing charges. Connecting these potentials with a conductor allows electric charges to flow, balancing out the difference. We call this flow an electric current. In contrast, a magnetic field does not produce such a flow between its poles. Magnetic fields influence other magnetic materials or moving electric charges, but don’t directly cause electric currents.
Magnetic Fields
If magnetic monopoles were to exist, would possess just one magnetic pole. While we haven’t been able to observe them, they are interesting to consider. All observed magnetic phenomena involve dipoles: entities with both a north and south pole.
Magnetic dipoles repel like poles and attract opposite ones. They can form “magnetic circuits” with other magnetic components. Magnets exhibit force lines, or flux lines, extending between their poles, visual representations of the field’s strength and direction.
Electric Fields
The fundamental units of electric charge are the electron, proton, and a few other subatomic particles. Similar to magnets, charged particles repel like charges and attract opposites. Charged particles exhibit electric fields around them. Grouping many charges amplifies this field. The voltage, or potential difference, between opposing charges causes electric currents when connected by a conductor.
Both electric and magnetic fields can influence electric charges in circuits and magnetic fields in magnets. However, their operation differs. Charges either “push outward” or “pull inward”, while magnets have fields around the entire object.
Moving a magnet near a charge or vice versa can cause the charge to move due to field interactions. However, we can’t transfer electric current between magnet and conductor. If you move a magnet close to a conductor and stop, any induced current will cease. Similarly, a static electric field doesn’t produce a magnetic field, but a changing one does. The interplay of motion between these fields in devices like generators is crucial for converting mechanical energy to electrical energy and vice versa.
Most electrical systems involve generators with moving parts to induce currents in conductors. The induced current travels to devices, powering everything from light bulbs to motors. The critical component is the interaction between changing magnetic and electric fields, enabled by motion. Check out “Potential Difference: The Driving Force Behind Electricity” for the next article in this series.
