Electrical Systems

Electrical Units 101

Electrical Units provides a foundational overview of electricity, including fundamental measures and terminology used to discuss electricity. Electricity is the flow of electrons, which are negatively charged particles. The amount of valence electrons in an atom determines how well it allows electricity to flow. There are two types of electricity, alternating current and direct current, but both flow from negative to positive. Current is measured by certain terms, including amperage, voltage, resistance, and wattage. Ohm’s Law and Watt’s Law describe the relationships between these values in a circuit.

When working with electrical systems, knowing how electricity flows and what different terms mean is very important. After taking this class, users should be familiar with the fundamentals of electricity and the vocabulary used to describe it. This enables users to build an understanding of more advanced electrical concepts and discuss them with the correct terminology.

  • Difficulty Beginner

  • Format Online

  • Number of Lessons 20

  • Language English


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Course Outline
  • Electricity
  • Parts of an Atom
  • Positive and Negative Charges
  • Atomic Numbers, Electrons, and Shells
  • Electricity and Atoms Review
  • Bonding
  • Conductivity
  • Producing Electricity
  • Circuits
  • Electrical Theory
  • Electron Transfer and Current Flow Review
  • Amperage
  • Voltage
  • Resistance
  • Ohm’s Law
  • Wattage
  • Electrical Measurements Review
  • Direct Current and Alternating Current
  • Advantages of Alternating Current
  • Final Review
  • Describe electricity.
  • Identify the parts of an atom.
  • Describe how positive and negative charges behave.
  • Define atomic number. Describe electrons in relation to shells.
  • Describe how atoms bond. Describe electron transfer.
  • Describe how valence electrons relate to conductivity.
  • Describe methods of producing electricity.
  • Identify the parts of a circuit.
  • Distinguish between conventional current theory and electron theory.
  • Define coulomb. Describe amperage.
  • Describe voltage.
  • Describe resistance.
  • Define Ohm’s Law.
  • Describe wattage. Define Watt’s Law.
  • Distinguish between direct current and alternating current.
  • Describe advantages of alternating current.
Vocabulary Term


Alternating current. Electricity that reverses direction at regularly recurring intervals of time. Alternating current switches direction 60 times per second, or 60 hertz, in the U.S.

alternating current

AC. Electricity that reverses direction at regularly recurring intervals of time. Alternating current switches direction 60 times per second, or 60 hertz, in the U.S.


A highly conductive, lightweight, silvery metal. Aluminum is often used in long-distance power distribution.


I. The strength or intensity of an electrical current. Amperage is measured in amperes (A).


A. A unit of measurement that indicates both an amount of electricity and the time it takes to travel a certain distance. One ampere, or amp, equals one coulomb per second.

atomic number

A number that identifies an element by indicating the number of protons in the nucleus of each of its atoms. The atomic number of each element is unique because every element has a different number of protons.


The smallest distinguishable unit of an element that retains that element's characteristics. Atoms are tiny particles that contain a nucleus and multiple shells.


A device that converts chemical energy into electrical energy. Batteries are a source of direct current.


An electrical force that links two or more atoms together. Bonds occur when atoms share or transfer electrons.


The joining of two or more atoms due to electrical force. Bonding occurs when atoms share or transfer electrons.


A nonmetallic material made from clay and hardened by firing at a high temperature. Ceramic materials are insulators.


A controlled path for electricity. A circuit includes a source, path, load, and control.


A material that allows free movement of electrons and therefore allows easy flow of electricity. Conductors are typically metals.


A component in a circuit that controls the flow of electricity. Controls determine when a circuit is energized.

conventional current theory

The belief that electricity flows out from a positive source to seek a negative object. Conventional current theory describes outdated beliefs about electricity.


A highly conductive, reddish-brown metal. Copper is often used as an electrical conductor in houses, buildings, and machinery.


C. The smallest quantitative measurement of electrical current. A coulomb of electricity is comparable to a drop of water.


The flow of electricity. Current strength is called amperage and is measured in amperes (A).


Direct current. Electricity that travels in one direction. Direct current does not reverse the direction of flow.

direct current

DC. Electricity that travels in one direction. Direct current does not reverse the direction of flow.


A form of energy created by the movement of electrons. Electricity can be converted into light, heat, or motion.

electromotive force

EMF. The pressure that pushes electrons through a conductor. Electromotive force is also called voltage.


A negatively charged particle that orbits the nucleus of an atom. Electrons flowing between atoms causes electricity.

electron theory

The belief that electricity flows out from a negative source to seek a positive object. Electron theory describes modern beliefs about electricity.


A basic substance consisting only of atoms that share the same number of protons. Elements include carbon, hydrogen, and oxygen.


A type of resistor that gives off heat and light. Filaments are used in light bulbs.


The number of complete AC cycles that occurs in one second. Frequency is measured in hertz (Hz).


A device that converts mechanical energy into electrical power. Generators use magnetic induction.

heat dissipation

The loss of energy that occurs when electrical current meets resistance. Heat dissipation can damage electrical equipment if there is too much.


Hz. A unit of frequency equal to one cycle per second. The hertz is used to measure how often the direction of alternating current reverses.

hydroelectric power

Electricity produced by turbines that are turned by water flow. Hydroelectric power converts the mechanical energy of the turbines into electrical energy.


A lightweight gas that is colorless and odorless. Hydrogen is the most abundant element on the planet.


A material that has little electrical conductivity and high resistance to electrical charges. Insulators include plastics and ceramics.


A charged atom. Ions may lose their charges if they gain or lose electrons.


A component in a circuit that converts electricity into light, heat, or mechanical motion. Loads include light bulbs, appliances, and machines.

magnetic induction

The use of magnets to cause voltage in a conductor. Magnetic induction is the basis for most electrical generators.


An attraction between materials having opposite electrical charges. Magnetism most often occurs between metals.


A hard substance that is electrically and thermally conductive. Metals are often described as shiny or lustrous in appearance.


The charge held by an electron in the shell of an atom. A negative charge is symbolized by a minus sign.


An atomic particle with no charge. Neutrons are located in the nucleus of an atom.


The central portion of an atom. The nucleus contains protons and neutrons while electrons orbit the nucleus.


Ω . The unit used to measure electrical resistance. One ohm is equal to one amp divided by one volt.

Ohm’s Law

The universal truth that describes the relationships between voltage, amperage, and resistance. Ohm's Law states that one volt equals one amp times one ohm.


A conductor that directs electricity in a circuit. Paths are often made of copper wire.


The charge held by a proton in the nucleus of an atom. A positive charge is symbolized by a plus sign.


The rate at which a device converts electrical energy into another form, such as heat or light. Power is measured in watts (W).


A positively charged particle within an atom. Protons are located in the nucleus of an atom.


R. The opposition to current flow. Resistance is measured in ohms (Ω).

schematic diagrams

An electrical print that uses symbols to represent all electrical components in a circuit. Schematic diagrams show the electrical relationships of all components, but not their physical locations.


A material that restricts electrons but still allows them to flow. Semiconductors, such as silicon, have more electrical conductivity than insulators but less than conductors.


A round path that electrons follow when they orbit a nucleus in an atom. Shells can have different numbers of electrons, depending on their positions, and atoms can have multiple shells.


A lustrous gray semi-metallic material. Silicon is a semiconductor.


A soft gray-white metal that has the highest electrical conductivity of all metals. Silver is often used as a conductor in electronic devices.

solar panel

A device that converts light energy into direct current electricity. Solar panels are made of semiconductors.


The device that provides electrical power to a circuit. The source is the origin of electricity, such as a power plant.


Having voltage in a circuit increased or decreased by a transformer. There is no effective way to transform DC.


A machine that uses the motion or energy of moving water or wind to produce circular movement. A turbine's mechanical motion is converted to electricity.

valence shell

The outermost orbit of electrons in an atom. The valence shell can have only eight electrons.


E. A measure of electrical pressure or potential. Voltage is measured in volts (V).


V. A unit used to measure electromotive force or pressure, which is called voltage. One volt of force is needed to cause one coulomb to do one unit of work.


W. A unit of measurement for the wattage or power used in or produced by a circuit. Watts require a change in energy to exist.

Watt’s Law

The universal truth that describes the relationships between wattage, amperage, and voltage. Watt's Law states that one watt equals one amp times one volt.


P. The amount of electrical power required by a device to work properly. Wattage is measured in watts (W).


The result of electricity flowing through some type of resistance. Work appears in the form of heat, light, or motion.