PHET Interactive Simulations: Radiating Charge

Topics

Electromagnetic Radiation
Dipole Radiation
Electric Field
Speed of Light

Description

The electric field lines from a point charge evolve in time as the charge moves. Watch radiation propagate outward at the speed of light as you wiggle the charge. Stop a moving charge to see bremsstrahlung (braking) radiation. Explore the radiation patterns as the charge moves with sinusoidal, circular, or linear motion. You can move the charge any way you like, as long as you don’t exceed the speed of light.

Sample Learning Goals

How the radial field line density depends on the speed of a charge in linear motion (compression of field lines).
How the anisotropy of the field pattern depends on sinusoidal vs. circular motion.
How the applied force and motion are related in relativistic dynamics (constant force does not result in faster-than-light travel).
How acceleration produces transverse fields, while constant velocity produces radial fields.
For sinusoidal motion, which produces dipole radiation, the field lines evolve from radial and static-like nearby, to transverse and plane-wave-like far away.
How sudden deceleration of a charge produces bremsstrahlung (braking) radiation.