Study Guide

# Electromagnetism Terms

## Electromagnetism Terms

### Charge Distribution

The distribution of charged butter all over an object.

### Charge Density

The quantity of charged butter over a line, area, or volume. Its units are charge per unit of distance, area, or volume accordingly.

### Electric Force, F

Two electric charges that like or dislike each other will either feel an attractive or repulsive force, differentiated by a positive or negative sign.

### Electric Field, E

Every charge has one of these, whether it likes it or not. It’s used to communicate with other charges. It’s the electric version of gravity: any object with mass has a gravity field extended out into space to interact with any other object with mass.

### Coulomb’s Law

The Coolomb law. Does a charge think another charge is attractive? If so, it’ll try to move towards it to hang out. If it’s not of interest, it’ll shy away.

### Electric Flux, ΦE

A crowd of electric field lines flowing into a surface area, calculable by multiplying the field by the area. Oh, and angle matters too:

### Current, I

Moving charges along a wire or in any conductive material, like the current in a river or cars in the street.

### Current Density

The current per cross-sectional area in a wire (or other conductive material).

### Charge Continuity

The cars that go into a traffic jam equal the cars that come out (hopefully). It’s definitely true for electric currents, if not for cars.

### Electric Dipole

The separation of a single positive and single negative charge over some small distance, on the order of distances between atoms or atoms within molecules.

### Electric Dipole Moment

A measure of the polarity of the electric dipole, p = qd. It’s kind of like the moment of inertia, but for electric fields.

### Electrostatics

The study of unchanging electric fields. Not static as in static electricity, but static as in constant with unmoving charges. To be fair, static electricity is so named because the charges stay put until we reach for the light switch after shuffling down the carpet in fuzzy socks.

The change in a magnetic field induces a current in a conductor because it induces an electromotive force (electric potential). It’s how induction ovens work.

### Lenz’s Law

The current induced by a changing magnetic field will always create a field opposite in direction to the one it’s passing through.

### Polarization

What happens when an electric field distorts the charge distribution, forcing one side to be positive and the other negative. It’s like politics.

### Electronmagnetic Induction

The ability to induce a current by changing the magnetic field. We hope this is in no way similar to politics.

### Lorentz’ Force

In the case of currents, F = Il × B. The three vectors are perpendicular to each other, as described by the right hand rule.

### Magnetic Force, FM

The force experienced by a charge or magnetic material within a magnetic field. We know. Circular definitions. See “magnetic field.”

### Magnetic Field, B

Every current and magnet has one of these, whether they like it or not. It’s used to communicate with other magnets and other currents, and it runs from North to South. It’s commonly determined from either Biot-Savart or Ampere’s Law. No one knows for sure why “B” was chosen to represent a magnetic field….

### Magnetic Flux, ΦM

The magnetic field lines flowing into a surface area, found by multiplying the two together while considering the angle between the field and the area: .

### Magnetic Dipole

A closed loop of current that obeys the whims of a magnetic field, B by creating on either side of the closed loop a magnetic north side and south side, so it’s not quite East Side Story.

### Magnetic Dipole Moment

The magnetic inertia of a closed loop of current, μ = IA, similar to the rotational moment of inertia in Newtonian physics but for magnets.

### Magnetostatic

The study of steady magnetic field as created by a constant electric current or a sedentary magnet.

### Electromagnetic Force

The force that results from marrying Ms. Electricity and Mr. Magnetism together. No really, it’s a combination of the two forces, which have an infinite reach like gravity does.

### Electromotive Force, EMF, ε

The electric potential, as in voltage of a battery or a changing magnetic field.

### Maxwell’s Equations

The four equations and rules of their marriage, set by the all-mighty God (of electromagnetism).

### Oscillating Circuit

A type of indecisive circuit that bounces back and forth between electric and magnetic energy from its combination of a capacitor and an inductor. Just can’t make up its mind.

### LC Circuit

A circuit with both a conductor and an inductor in it, creating an oscillating circuit.

### Permitivitty, ε

How good a material is at storing electric energy in the presence of an electric field.

### Permeability, μ

In electricity and magnetism, it means how responsive a substance it to magnetic flux in the presence of a magnetic field.

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