Ohms, Amps, Volts and Watts

December 13, 2017 by Ben Stowe, CTS

Electricity is the lifeblood of the systems we run, so having a basic understanding of it can be very helpful for engineering and operating reliable systems. Moreso, it can be essential in troubleshooting them when things go wrong.

While there are a great many electrical terms, four fundamentally important ones are Ohms, Volts, Amps and Watts. These are all units of measure and they are intertwined in electrical relationships known as Ohm’s Law and Watts Law.

Ohms law tells us that Ohms are equal to volts divided by amps, while Watts law tells us that Watts are equal to Volts x Amps. Using these two basic formulas, we can calculate to find 2 unknown values if we know any other 2.

Named for Georg Simon Ohm, the Ohm is a unit of measurement for the resistance in an electrical circuit. A device with greater resistance will have a higher ohm value associated with it. Many times, we see ohm values for loudspeakers. While this correlates to impedance, which is similar but fundamentally different than resistance, for the purpose of this article, we’ll treat them as one and the same. Therefore, an 8 ohm loudspeaker presents more resistance to an amplifier than a 4 ohm loudspeaker does.

In honor of Alesandro Volta’s work, we have the Volt. Voltage is the electrical potential of the circuit. It is present whether electricity is flowing or not. A good example of this is a battery, or an outlet. At an outlet in the wall there is approximately 120 volts available, whether a device is plugged into it or not. Think about this like water pressure. It’s present even when the faucet is turned off.

Amps, short for Amperes, named for Andre Marie Ampere, measure the current, or electrical flow of a circuit. They are also the typical value found on circuit breakers and fuses. The greater the flow of electricity, the greater the value in amperes. Because of Watts law, we know that to create 1000 watts from a 120 volt power outlet, we need 8.33 amps of current.

Watts, named for James Watt, measure electrical power. Many times we see watts listed as a measurement for a loudspeaker. While they measure how much electrical work is being accomplished, they are not good representatives of how loud or otherwise effective it is. No more so than using wattage to compare the brightness of an incandescent lamp and an LED lamp. Wattage can be helpful when matching amplifiers to loudspeakers, or when determining what the appropriate size circuit to supply a system is. Using Watts law you can determine the number of amps necessary at your circuit breaker when you know the Watts and Volts.

Ben Stowe, CTS Ben Stowe, CTS (26 Posts)

Ben’s love of electronics and technology led to years of schooling in Electricity, Electronics, Robotics and Lasers. Ben supported himself through school by building and selling strobe lights and other electronic devices. He built his first DJ show largely from scratch and scrap, often repairing broken items others had thrown away because he could not afford to buy new equipment. He holds a Minnesota electrical license, and his AV installs have been featured in almost every major industry trade magazine. His relentless passion for education has led to a number of other certifications and accreditations, including the most widely recognized one in the AV industry, the InfoComm CTS. His love for education inspired him to begin the ProAcademy educational sessions, focused on increasing understanding of AV technologies within the industry. Ben has been involved in a number of technical writings, lectures, presentations, as well as research and development assistance with a number of manufacturers for products, industry wide. He is also a regular contributing author to industry magazines in the United States and Europe. Ben’s presentations have been featured across the world both as a part of industry leading trade shows, and as a presenter for various groups and functions. Some of these events include BPM in the United Kingdom, Mobile Beat, the ADJA National Convention, Wedding MBA, and a national tour as a headlining presenter for an industry magazine. The United States Armed Forces branches have also called upon Ben to provide engineering and training assistance. His highly informational, slightly nerdy and always funny presentation style have made him a favorite at events, while his sincere desire to help people with their application of technology have made him a favorite with them after the event. Ben serves the industry as the President of NLFX Professional, an industry leading supplier of sound, lighting and video systems, a role he has maintained since founding the company in 1993.

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