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Motion of charge in uniform field
Intermediate
A charged particle accelerates along field lines.
a = qE/mA charge q of mass m accelerates uniformly a = qE/m. An electron in a 1000 V/m field accelerates at 1.8×10¹⁴ m/s².
Path in a perpendicular field is a parabola.
Ignore gravity for electrons.
In more detail
A charged particle in a uniform electric field accelerates in a straight line, with acceleration a = qE/m. This is similar to projectile motion, but driven by an electric force.
Real-world uses
- Electron guns in old televisions accelerate electrons in uniform fields.
- Mass spectrometers use fields to separate ions.
- Particle accelerators use uniform electric fields to speed up electrons and protons along a straight path.
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Frequently asked questions
Is a uniform field like gravity?
Yes, with acceleration qE/m instead of g.
Does mass matter?
Yes, lighter particles accelerate more for the same field.
Does a charged particle always follow field lines?
Only if it starts at rest or moves along the field, because its inertia makes it curve away from a field line otherwise.
Related topics in Electrostatics
Lightning and discharge · Photocopiers and electrostatic precipitators · Millikan oil drop experiment · Cathode ray tube · Method of images · Poisson's and Laplace's equations