When playing with a piezoelectric spark device taken from a lighter, I created a spark between it and a radiator, and noticed two effects. First, the room lights flickered (the dimmer switch for my lights was partly on, so this may be a factor). Second, when I produced the spark, it caused my computer to declare that the devices plugged into its USB ports had been removed. What caused these effects?
鈥� The lighter is designed to generate sparks only powerful enough for ignition, but the radiator, because it was earthed, drew sparks larger than those intended to jump between the lighter鈥檚 electrodes. Electrical sparks generate electromagnetic pulses in the form of radio waves and these pulses interfere with all sorts of devices, so manufacturers of various equipment avoid making unnecessarily large sparks.
To appreciate the power of such pulses, remember that for the first several decades of radio technology, radio transmitters used sparks, which is why radio operators were traditionally nicknamed 鈥渟parks鈥�.
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Electromagnetically speaking, sparks 鈥� lightning in particular 鈥� are very noisy. These radio pulses induce electrical surges in all sorts of conductors, including your dimmer switch and the connections to USB ports.
The dimmer just received a few flicker-inducing jolts, but USB ports operate on their own very high frequency and tightly encoded pulses. Surges caused by the radio pulses your sparks generated would be as confusing as numbers shouted into a telephone conversation in which people were trying to whisper numeric messages. On detecting the nonsense, your computer might well have concluded that there were no working devices on those ports.
Such problems are the reason for regulations demanding that electromagnetic noise from commercial devices be kept to a minimum.
Jon Richfield, Somerset West, South Africa