Home / Topics / AC Circuits & EM Waves
EM wave generation
Intermediate
Accelerating charges radiate EM waves.
Accelerating charges radiate; an oscillating current in an antenna produces self-propagating E and B oscillations. Hertz demonstrated them in 1887.
A radio mast radiates at its drive frequency.
Steady current doesn't radiate.
In more detail
Electromagnetic waves are produced by accelerating charges, which create changing electric and magnetic fields that propagate outward. Antennas radiate waves by oscillating charges at radio frequencies.
Real-world uses
- Radio transmitters generate waves by oscillating currents in antennas.
- Light is produced by accelerating electrons in atoms.
- Radio and TV transmitters work because accelerating charges in an antenna radiate electromagnetic waves.
Open the interactive lesson, with simulation and quiz →
Frequently asked questions
Do stationary charges emit waves?
No, only accelerating charges radiate electromagnetic waves.
How are radio waves made?
By oscillating currents in an antenna at the desired frequency.
Do charges need to move at high speed to radiate?
No. Any acceleration produces radiation, which is why the oscillating charges in an antenna are so effective.
Related topics in AC Circuits & EM Waves
Three-phase power · Rectification and smoothing · Displacement current · EM wave properties · Speed of light · EM wave equation