Kathy Jolly, of Caversham, asks :-

I have a touch-lamp as my bedside lamp. It regularly makes a buzzing sound like a transformer. Would that effect someone's health?

Martin Gledhill, a physicist at EMF Services, responded.

The buzzing could be caused by a couple of things: either the filament in the bulb vibrating (especially if the touch lamp allows you to control the brightness), or a choke (electrical component in the lamp control, like a coil) vibrating. The vibrations are caused by the alternating currents which provide power to the lamp. If there is a dimmer control, changes in the alternating current are abrupt, and produce abrupt changes in the magnetic fields around the filament (or choke). These changes can produce small movements, especially in the iron transformer or choke cores, and hence the buzzing sound.

Apart from the annoyance, the buzzing sound itself is harmless. Like any electrical equipment, you will also find electric and magnetic fields around the lamp, at frequencies of 50 and (probably) 100 Hz, and maybe some higher harmonics. The fields around a lamp are quite low because the lamp does not take much current, and just tiny fractions of levels which could cause any health effects.

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(http://science.howstuffworks.com/innovation/science-questions/touch-sensitive-lamp.htm)