unit

volt per metre

volt per metre — from formula anatomy
13 related articles

Description

The volt per metre (V/m) is the SI unit of electric field strength. It describes how strongly an electric field pushes on a charged particle: one volt per metre means a potential difference of one volt exists across a distance of one metre. This unit ties together voltage (energy per charge) and distance, making it the natural measure of field intensity in circuits, capacitors, and electromagnetic waves.

History

The unit derives from the volt, named after Alessandro Volta in the 19th century, and the metre, standardized during the French Revolution. The explicit use of V/m as a field unit became standard with the development of electromagnetic theory in the late 1800s.

How it works

An electric field E is defined as the force per unit charge, but it also equals the negative gradient of electric potential: E = -dV/dx. So if you place two parallel plates one metre apart and apply one volt between them, the field between them is 1 V/m. The unit is equivalent to newtons per coulomb (N/C), since a volt is a joule per coulomb and a joule is a newton-metre.

In practice

Used to specify electric field strengths in high-voltage engineering, to set safety limits for electromagnetic exposure, and to characterize the fields in particle accelerators and capacitors.

Fun fact

The electric field of a typical lightning bolt is about 10,000 V/m — enough to ionize air and create a conductive path.

Concept graph →

Related articles · 13

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