Fields

Fields are basically forces that interact with & affect other forces. There are four fundamental forces: strong, weak, gravity, & electromagnetic. It’s the electromagnetic forces inside of atoms that allow them to behave the way they do. The force exerted by a positive charge will attract the force exerted by a negative charge, & the force exerted by a positive charge will repel the force exerted by another positive charge. Like forces repel each other & opposite forces attract each other. Fields, or forces, is the glue that holds everything in the universe together.

Without these forces, the universe would truly be a dull & non-forming place for elementary particles to exist & nothing more. Atoms wouldn’t exist. Planets wouldn’t exist. Stars wouldn’t exist. Basically, anything that you’d call a body could not be.

Electric Fields

Electric fields arise from the electrical charges of atoms. As you may already know, atoms consist

of protons, neutrons, & electrons. The protons & neutrons make up the nucleus, or center, of

the atom. The outer part, or orbit, of the atom consists of electrons. Protons carry positive charges, while neutrons carry no charges & are there to prevent protons from repelling each other in the nucleus (since like charges repel each other & opposite charges attract each other). Electrons carry negative charges. Both protons & electrons emit electrical fields which are forces that attract & repel other types of fields. Positive charges will attract negative charges & vice versa. It’s the positive charges of protons in the nucleus that keep electrons orbiting around the nucleus. Without an opposite force to attract the electrons, the electrons would float out & away into space!

An atom that is not electrically charged has an equal number of electrons & protons. Some atoms have free electrons that can move to other atoms. When this occurs, the atom giving up an electron has an overall positive charge, since it now contains more protons than electrons. Similarly, when an atom gains an electron, it has an overall negative charge, since it now

                                                                                                

contains more electrons than protons. An atom that contains an electrical charge is called an ion.

When an atom contains an equal number of protons & electrons, the fields produced by the

protons & electrons cancel each other out, & the atom has an overall neutral charge, or no

charge. However, when an atom contains an unequal number of electrons or protons, an electric

field is produced by the atom because of its overall negative or positive charge.

An atom that carries an electrical charge emits an electric field that can attract or repel opposite

& like electrical fields respectively. Electrical fields are measured in volts per meter (V/m). The

higher the electrical charge in a material, the higher the Voltage, & the higher the electric field

around the material will be. An electric field is strongest nearest its source, or atom, whereas it

becomes weaker & weaker as it moves further & further away.

Electric fields are invisible to the naked eye. However, you can readily observe their effects. For

example, when you rub a piece of dry glass against a piece of silk, you are removing some of the

electrons from the atoms of the dry glass to the atoms of the piece of silk. When this happens, the

silk piece is now negatively charged, & the piece of dry glass is now positively charged. If you

were to touch the piece of dry glass to the piece of silk, a transfer of electrons would flow back to

the dry glass, as opposite electrical charges attract each other. If the charge is great enough, you

can often see a spark occur as a result of the transfer of electrons between the two materials

through the air.

Magnetic Fields

Magnetic fields arise from the movement of electrical charges. As opposed to electric fields, which are produced by stationary charges, or ions (called static electricity), magnetic fields are produced whenever an electron or proton in an atom moves. Electrons in an atom can move in three different ways: 1) around the orbit of an atom, 2) on their axes (like the spinning of a ball), or 3) to another atom. The magnetic field produced by electrons rotating around an atom and on their axes is very small. It’s when electrons move from atom to atom that a greater magnetic field is produced.

Electrons are arranged in an atom in groups called domains. Each domain consists of electrons

which spin on their axes in the same general direction. If an atom contains four domains, & two

of those domains contain electrons spinning in one general direction & the other two domains

contain electrons spinning in another general direction, no net magnetic field is produced that’s

strong enough to have any effect on the surrounding environment of the atom. However, when most of the domains of an atom contain electrons spinning in one general direction, the net magnetic field produced is strong enough to have an effect on the surrounding environment of the atom. This is how magnets work. In a bar magnet, most of the electrons in the magnet are spinning in one general direction.

 Imagine a magnet being a water hose with the water turned on. The water flows from one direction to another. Now imagine that the water flow is the result of a magnetic field pushing the water along the hose. At one end of the hose, where the water comes in, you have the South pole, & at the other end of the hose, where the water exits, you have the North pole. Magnets contain such poles: North & South poles, & they’re a result of how the magnetic field is produced from billions of moving electrons. Magnetic fields from a bar magnet flow from the South pole end of the bar, through the magnet towards the North pole of the bar, & then out into the air & then back into the South pole of the bar again. And since like fields repel each other & opposite fields attract, this would explain why opposite poles of magnets will stick together while like poles will not.

                                                                                                                    

The strength of a magnetic field is measured in Amperes per meter (A/m). Another common term

used for describing moving electrical charges is current. Electrical currents are commonly

measured in amperes. However, this type of measurement is done very close to the source of the

current. When the magnetic field needs to be measured at a distance from its source, such as in

space, another type of measurement is employed called magnetic flux density. The measuring

units used to measure magnetic flux density are gamma, Tesla, & Gauss. These are the units of measurement commonly used in EMF meters.

Electromagnetic Fields (EMF)

Electromagnetic fields arise from the combination of electric & magnetic fields. Electric fields are produced by charges within an atom while magnetic fields are produced whenever those charges move. So, if an electron within an atom moves, either within itself or to another atom, it produces a magnetic field. Electrons are negatively charged particles. So, they always produce a certain amount of electric fields. The same goes for the positively charged protons. Also, electrons are always spinning on their axes which indicate they are moving &  hence, producing magnetic fields. So, it’s safe to say that if electrons are charged particles & they are always moving that they are always producing electric & magnetic fields. The resultant field produced by such a phenomenon is called the electromagnetic field. It’s the product of the overlapping of electric & magnetic fields.

An electric field that moves, or changes, will generate a magnetic field. A magnetic field that moves, or changes, will generate an electric field. It’s for these reasons why generators can produce electricity & electricity can move electric motors. In a generator, a moving magnet, powered by some other energy source such as gasoline, produces changing magnetic fields that produce electric fields in conductors (wires designed to carry electricity), & , hence, electricity in the form of electrical current (moving charges/electrons). In an electric motor, an electric current produces magnetic fields that force magnetic materials to move (much like a compass moves with the magnetic fields of the earth).

When electrical charges, either positive or negative, change at regular intervals (oscillate), they

produce electromagnetic waves: oscillations of overlapping electric & magnetic fields.

Electromagnetic waves are the combination of electric & magnetic waves overlapping at right

angles to each other, & they travel out into space at the speed of light. Another term used to

describe electromagnetic waves is electromagnetic radiation. Light is a form of electromagnetic

radiation. Light travels very fast at the rate of 299,792,458 meters per second (in a vacuum).

Electromagnetic radiation can travel very long distances. That’s because an electromagnetic wave is self-propagating: the moving magnetic field (in the form of a wave), because of the fact that it’s moving, produces an electric field that also moves with the movement of the magnetic field, & the moving electric field (in the form of a wave), because of the fact that it’s moving, produces a magnetic field that also moves with the movement of the electric field. In other words, since moving magnetic fields generate electric fields & moving electric fields generate magnetic fields, a self-propagating electromagnetic field in the form of a wave is produced. It’s a self-sustaining marriage that makes phenomena like light possible. It’s also what makes TV, radio, microwave ovens, & cell phones possible.

Electromagnetic waves travel at varying frequencies. Frequencies are rates at which waves travel

within a certain period of time. For example, the electricity that’s typically used via a monitor screen operates at a frequency of 60 Hertz. One Hertz is the time it takes for once wave cycle to form in one second. The higher the frequency, the more cycles can fit into a period of time. Light, a form of electromagnetic waves, travels at very high frequencies: between 430 trillion & 750 trillion Hertz. Our human eyes can pickup these frequencies as light – it’s what allows us to view the world around us.