# What is a Voltmeter? - Definition & Uses

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• 0:00 What Is a Voltmeter?
• 0:54 Common Uses
• 4:22 Lesson Summary

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Lesson Transcript
Instructor: Christopher Biagi

Christopher has a diverse and interdisciplinary education focussing on electromagnetic science and engineering.

Voltmeters are ubiquitous in our world and critical to technology. In this lesson, you will learn what a voltmeter is, how it works, and how it's used.

## What is a Voltmeter?

Voltmeters provide a way to safely measure the voltage, or the difference in electric potential, between two points in a circuit while not changing the voltage in that circuit. The capability to measure voltage is critical to designing and maintaining advanced technology, but it also has more common and practical applications.

For example, suppose it's a hot day and you decide to cool off with a fan, but when you plug it in and turn it on, nothing happens. Is the fan broken? Perhaps, but it is possible that the outlet is not receiving electricity. A voltmeter could be used to measure the voltage at the outlet, and if it is not around 120 volts, then the wall outlet could be broken.

Another instance where a voltmeter could be used is to determine if a battery is charged or drained. When troubleshooting a car that will not start, measuring the battery voltage with a voltmeter is a good place to begin.

## Common Uses

The examples given above are typical examples of how measuring voltage on common, everyday devices can be useful. In today's modern world, voltage is used in many applications at many different magnitudes. Power transmission lines carry electricity at varying levels of high voltage, up to hundreds of thousands of volts, which is much greater than the 120 volts at your wall outlet. The electronics in the device you're using to read this lesson require precise voltage control, but operate at only a few volts and can be sensitive to fractions of a volt. As you can imagine, there are different types of voltmeters for these widely varying applications.

Voltmeters that are made to measure dangerously high voltages, such as on transmission lines, have large probes with extra electrical insulation between the test points and the user in order to prevent the user from being shocked. Other voltmeters are made to measure very low levels of voltage on very small objects with intense precision, such as computer chips. Voltmeters for these applications can be very small, and are specially designed to minimize or eliminate unwanted noise from potential differences that exist in the air naturally, or due to nearby electronics.

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