Electrical Terminology: Volts, Ohms, Amps, and Watts

Most of the common electrical terms get their names from the people who helped develop the concepts. Let’s look at what some of the common electrical terms mean.

Alessandro Volta was an Italian physicist and a pioneer of electricity and power. He is credited as the inventor of the electrical battery.  The scientific unit of electrical potential is named in his honor. Volts, or voltage, is a measure of the force in an electrical system.  The average house has 240 volts of electricity available to it.  In homes, we can split the 240 volts into separate branches with 120 volts of power supplying most outlets, or keep it together with 240 volts of potential at some outlets.  Standard plugs and outlets are fit to run items on 120 volts.  Special plugs are used when appliances or equipment require a higher voltage to operate.

Electrical potential (or volts) exists even if there is no electricity flowing in the house.  Even when everything is at rest, there is this tremendous force in the house waiting to be unleashed.  This is one of the reasons electricity is dangerous. Items may be energized with 120 or 240 volts of electric potential and because you can’t see electricity, you can’t tell. Since the human body is a good conductor, we provide a nice place for that force to be released. In much the same way that spilled water wants to find the lowest level, areas of high electrical energy want to flow to areas of low electrical energy. The ground has zero electrical energy or potential, therefore, everything that has 120 volts or 240 volts stored up in it would love to release all its pent-up energy into the ground. If you happen to be standing on the ground and touch something that has substantial electrical potential energy, you will be the conductor that allows that energy to be released into the ground. This is what hurts or kills people.

It is tricky, but important to understand, that the voltage is not what kills you. Until the electricity starts to flow, there is no energy released and you can’t get hurt. For example, if you could hover in mid-air and touch something that had 240 volts of energy, you may not feel a thing.  This is because air is a good insulator and the electricity can’t get through you to the ground if you are floating in midair. The air between you and the ground acts as an insulator and no electricity flows. Even though you’ve touched something with a huge voltage you may not be adversely affected at all. This is why birds can sit on above ground electrical service wires and not get fried.

George Ohm was a German physicist that began to research the battery invented by Alessandro Volta. Using equipment of his own creation, Ohm found that there is a direct proportionality between the potential difference (voltage) applied across a conductor and the resultant electric current. This relationship became known as Ohm’s Law.  All conductors don’t allow electricity to flow freely because each material has some properties of resistance. Insulators have the ability to substantially resist the flow of electricity.  The resistance of an electrical circuit is measured in ohms, and is determined by the size, length, temperature, and material that the electricity is trying to flow through.

If the resistance is large enough, no electricity will flow. As the resistance decreases, more electricity will flow. If the resistance is almost nothing, electricity will flow freely. When we put something in a circuit that we want to glow brightly (a light bulb), get warm (a heating element), or do some mechanical work (a motor), each of these appliances is a resistor. They are designed to allow a certain amount of electricity to flow. The appliances convert that electrical energy into light, heat, or mechanical force. In a household circuit, the electrical potential of 120 volts flows readily through the distribution wiring, but has to fight its way past resistors such as light bulbs.

Andre-Marie Ampere was a French physicist who founded the science of electrodynamics. The scientific unit of electric current is named after him. Amperes are a measure of how much electricity is flowing through a circuit.  It is important to understand that amps are the result of a fixed voltage (force) pushing on a circuit of fixed resistance.

For electricity to flow, there has to be a path from the source of high potential energy to the ground (a point of very low electrical potential). If we have a pressure of 120 volts and a huge resistance, there will be no electrical current flowing and no amps measurable. We call this an open circuit.

If the resistance is lowered (for example, by closing a switch), then electricity can flow through the circuit to the ground. The amount of resistance that the electricity encounters will determine how much current flows. The larger the resistor, the smaller the flow. The smaller the resistance, the larger the flow. If there is no resistor in the circuit, there will be very little resistance and tremendous flow. Electricians talk about this as a short circuit. This should blow a fuse or trip a breaker. Too much electrical flow is a bad thing because wires will overheat and melt. If the resistors are sized appropriately and the current flow is what we wanted, light bulbs will glow, but will not melt, heating elements will give off heat, but not break apart, and electric motors will turn, but not overheat.

James Watt was a Scottish inventor and a mechanical engineer who’s steam engine was fundamental to the changes brought by the Industrial Revolution. He developed the concept of horsepower and the scientific unit of power is named after him.

Watts are a measure of the rate of electrical energy being used or consumed. The amount of energy depends on the voltage and the resulting current. In fact, to calculate watts, you simply multiply the voltage times the current. You may be familiar with this from your electric bill. We pay for electricity using units called kilowatt hours. The amount of electricity we consumed is measured by taking the rate at which we consume it while keeping track of how long we consume it.  The more you consume, the higher your bill will be.

Check out these handy diagrams below to help put all these ideas together.

At Parkwood Property Inspections, we aim to help educate our clients in the way their homes work. Because we have a solid understanding of the basics on important topics, such as electricity, we are better prepared to answer any questions you may have during the home inspection process. If you are in the Piedmont Triad area of NC, we look forward to working with you.