# Introduction to Electricity – EMF, Field Strength, Conductance, and 3 Types of DC Voltage

• The only particle that moves when an electric circuit is completed is the electron. For this reason, electricity is described as the flow of electrons.
• In the atom, there are 3 fundamental particles – proton, electron, and neutron. The proton and neutron form the atomic nucleus and give the atom its mass. The proton and electron are collectively designated as electrical particles because each is surrounded by an invisible field of force that reacts in an electrically negative or positive manner (respectively) with the adjacent matter. This means that the electron has a negative charge, while the proton has a positive charge.
• The mass of the proton is 1800 times the mass of the electron, but each electrical particle has a unit (one) electric charge, i.e + and -.
• The basic law of charges: Like charges repel, unlike charges attract. Because of differences in mass, the proton remains stationary when it attracts the electron, which implies that only the electron moves. This ordered flow of electrons is called a current. Likewise, in terms of mass-to-charge ratio, the electron has a stronger field of force than the proton.
• When an atom loses or gains an electron it becomes an ion. If it loses an electron, it becomes a positive ion. If it gains an electron, it becomes a negative ion.
• The power of this invisible field of force is called the field strength. This field strength varies inversely with the distance of the field from the electrical particle using this proportion:

Field Strength α 1 / (distance squared)

• The field strength of electrical particles is directly proportional to the number of these particles.
• The invisible field of force around an electrical particle is called the electrostatic field. When an electron moves, then it moves with its electrostatic field, and this moving field creates dynamic electricity. To cause this electron to move, then it needs to be pushed by a negative field strength or be pulled by a positive field strength.
• Heavy atoms are usually unstable and decompose to form stable atoms. The atom that undergoes decomposition by emitting energy is called a radioactive atom.
• Matter made up of only one type of atom is called an element, but if it is made up of two or more different atoms, then it is called a compound.
• In the atom, the electron orbits around the nucleus – which is made up of protons and neutrons (except for the hydrogen atom). This orbiting electron is called an orbital or planetary electron.
• Each atom has an orbital shell(s) depending on the number of electrons, and the further the electron is from the nucleus, the less strongly it is bound to the nucleus. This, the electron in the outermost orbital is least strongly bound to the nucleus as compared to the electron in the innermost orbital shell. The orbital shell that surrounds the nucleus can hold 2 electrons and is called the innermost shell, and the shell surrounding this innermost shell can hold a maximum of 8 electrons, and the next outer shell can hold 18 electrons. The electron that is tightly bound to the nucleus is called the valence or bound electron, while the loosely bound electron in the outermost orbit that can move away from the nucleus is called the free electron. To move this free electron, there is a need for energy input to overcome the resistance of the nucleus to allow for the movement of this electron.
• Current (I) flows in a conductor if enough electron-moving force is applied to cause an ordered flow of electrons. This electron-moving force is called electromotive force (EMF) (or electric pressure, electric potential, or potential difference [PD]), and its unit of measurement is the Volt (V). The unit of measurement of current is the Ampere (A). When EMF is applied to create a current flow, there is an opposing force to this current flow in the conductor, and this opposing force is called resistance (R), and it’s unit of measurement is Ohm (Ω). The ampere is the number of electrons orderly flowing through a point in a circuit in one second, and this number of electrons is measured as Coulomb (C). One C is 6.25 × 1018 electrons, and 1 Coulomb-per-second is called an Ampere.
• Any material without free electrons cannot conduct current, and is thus called a non-conductor or insulator. Glass is a good insulator, while silver is a good conductor.
• The simple electric circuit has 4 main components: the source (of EMF), (conducting) wires, load, and control device (usually a switch).
• There are 4 types of current:
1. Direct current (DC): Current flows in the same direction with no variation in its strength (amplitude) and EMF.
2. Varying DC: DC whose current and voltage vary, though neither falls to zero.
3. Pulsating DC: DC whose current and voltage vary, with either periodically falling to zero.
4. Alternating Current (AC): The direction of ordered electron flow reverses periodically, and this is associated with changes in current amplitude.
• The resisting ability of a wire is determined by the following 4 physical attributes:
1. Material the wire is made of.
2. Length of wire.
3. Temperature of wire.
4. Cross-sectional area of the wire.
• Resistance in the wire can be calculated using this formula:

Resistance (in Ω) = ρ (resistivity of material) × Length (in meters) / Cross-sectional Area = R= ρL/A.

ρ is the resistivity of the material of the wire, and it’s unit of measurement in ohm-meter (Ωm).

• The reciprocal of resistance is called conductance, which is the measure of how of the ease of current flow in a material. Conductance (G) is calculated as 1/R and its unit of measurement is the siemens (S).
• The best conductor of electricity is silver, and for this reason, it has been assigned the relative conductivity value of 100%. This allows other conductors to have their conductivity measured in relation to silver e.g copper has a relative conductivity of 96%. Gold and aluminum have relative conductivity of 73% and 59% respectively.