Many processes in electromagnetism vary with time. Some of them are well known, in particular those
related to line frequencies of 50 Hz or 60 Hz such as fluctuating light output of discharge and
incandescent lamps. The flickers of discharge and incandescent lamps have quite different physical
principles involved, which are investigated experimentally using high-speed cameras and
theoretically using simplified models. The topic is related to other phenomena such as the transient
behaviour of phosphor layers covering the screen of oscilloscopes and the time-varying Lorentz force
acting on the filament of light bulbs. All studies are well suited for teaching selected aspects of
electromagnetism and light at undergraduate level at university.