Glossary term
Electric Field
A vector field describing the force per unit electric charge at a point in space.
Definition
quantityA vector field describing the force per unit electric charge at a point in space.
Electric field is a fundamental electromagnetic quantity used to analyse insulation stress, capacitors, sensors, semiconductor devices, electrostatic discharge, high-voltage equipment, electromagnetic compatibility, and wave propagation.
Electric field describes how an electric charge would be forced at a point. It is defined as:
where \mathbf{F} is force and q is charge. In electrostatics, electric field is related to electric potential by:
so field strength is the spatial rate of change of voltage.
Engineering role
Electric field is central to insulation design, capacitors, high-voltage clearances, printed circuit board spacing, semiconductor junctions, sensors, antennas, electrostatic discharge, and electromagnetic compatibility. Breakdown, corona, leakage, arcing, and partial discharge are all linked to local electric-field stress.
Field concentration
Geometry strongly affects electric field. Sharp edges, points, small radii, voids, interfaces, and contamination can concentrate field and create local stress much higher than the average voltage divided by distance. This is why high-voltage equipment uses grading rings, smooth electrodes, shielding, insulation coordination, and controlled creepage and clearance distances.
Materials and media
The same applied voltage can produce different field distributions depending on permittivity, conductivity, moisture, temperature, and material interfaces. In insulation systems, field distribution may change over time because of space charge, aging, contamination, and partial discharge damage. In semiconductors, electric field controls carrier motion, depletion regions, breakdown, and device switching.
Measurement and modelling
Electric fields can be inferred from voltage gradients, field probes, capacitive sensors, electro-optic methods, or electromagnetic simulations. Models must define boundary conditions, material properties, electrode geometry, and whether the field is static, low-frequency, transient, or part of a propagating wave.
Common mistakes
Common mistakes include using average field as if it represented local peak field, ignoring edge effects, and assuming air-gap breakdown values apply to contaminated, humid, pressurized, or small-gap systems. Engineers should also avoid treating creepage distance, clearance distance, and dielectric thickness as interchangeable design quantities.