Definition

root-mean-square (RMS)

Part of the Mathematics glossary:

Also see peak and peak-to-peak.

In a direct current (DC) circuit, voltage or current is simple to define, but in an alternating current (AC) circuit, the definition is more complicated, and can be done in several ways. Root-mean-square (rms) refersto the most common mathematical method of defining the effective voltage or current of an AC wave.

To determine rms value, three mathematical operations are carried out onthe function representing the AC waveform:

  • (1) The square of the waveform function (usually a sine wave) is determined.

  • (2) The function resulting from step (1) is averaged over time.

  • (3) The square root of the function resulting from step (2) is found.

In a circuit whose impedance consistsof a pure resistance, the rms value of an ACwave is often called the effective value or DC-equivalent value.For example, if an AC source of 100 volts rms is connected across a resistor, and theresulting current causes 50 watts of heat to be dissipated by the resistor, then 50 wattsof heat will also be dissipated if a 100-volt DC source is connected to the resistor.

For a sine wave, the rms value is 0.707 times the peak value, or 0.354 times thepeak-to-peak value. Household utility voltages are expressed in rms terms.? Aso-called "117-volt" AC circuit carries about 165 volts peak (pk), or 330 voltspeak-to-peak (pk-pk).

This was last updated in April 2005
Posted by: Margaret Rouse

Related Terms

Definitions

  • quant (quantitative analyst)

    - A quant (quantitative analyst) is a financial services professional whose qualifications also include advanced mathematics and and computer skills. Quants design complex mathematical models for us... (WhatIs.com)

  • statistical analysis

    - Statistical analysis is a component of data analytics. In the context of business intelligence (BI), statistical analysis involves collecting and scrutinizing every single data sample in a set of i... (WhatIs.com)

  • algorithm

    - An algorithm (pronounced AL-go-rith-um) is a procedure or formula for solving a problem. (WhatIs.com)

Glossaries

  • Mathematics

    - Terms related to mathematics, including definitions about logic, algorithms and computations and mathematical terms used in computer science and business.

  • Internet applications

    - This WhatIs.com glossary contains terms related to Internet applications, including definitions about Software as a Service (SaaS) delivery models and words and phrases about web sites, e-commerce ...

Ask a Question About root-mean-square (RMS)Powered by ITKnowledgeExchange.com

Get answers from your peers on your most technical challenges

Tech TalkComment

Share
Comments

    Results

    Contribute to the conversation

    All fields are required. Comments will appear at the bottom of the article.