OT: Computer's electrical outlet

Mikkel L. Ellertson mikkel at infinity-ltd.com
Fri Nov 16 04:15:42 UTC 2007

Dotan Cohen wrote:
> On 15/11/2007, Mikkel L. Ellertson <mikkel at infinity-ltd.com> wrote:
>> The popping sound may be because of the RF spike when the contacts
>> that turn on the heating element open or close. I have notices
>> amplified speakers with long leads to the speakers tend to be
>> sensitive to this.
> Do you say in English "induced current" when a changing magnetic field
> causes current to flow? What is the correct English term? It is this
> phenonenon to which I attribute the popping sounds.
Induced current is the proper tern, but I would expect a 60 cycle
hum rather then a pop from induced current. I suspect that the pop
is the wire between the computer and the speakers acting as an
antenna, picking up the signal generated when the thermostat in the
heater opens/closes, generating a small spark. (A spark-gap
transmitter.) This is then amplified by the amp in the speakers.

>> The things I would expect to cause problems are
>> the microwave and the refrigerator. They both tend to have fairly
>> high startup loads. This is known to cause a voltage drop. The
>> extent of the drop depends on the wiring. also, depending on the
>> type of fuse used, the spike may blow the fuse. Time delay fuses
>> handle it best, fast blow fuses handle it the worst. I suspect that
>> you have a time delay type fuse.
> I don't think that it's a time delay fuse because I recently did
> something stupid, and it tripped right away. I've never heard of a
> time delay fuse, but it sounds rather dangerous.
A time delay fuse is a dual element fuse that will accept a current
spike without blowing, but will still blow at the rated current.
Actually, a 10 amp fuse is only rated for 8 amps continues load. Mor
then 80% of the fuse rating for more then an hour will cause the
fuse to blow. The reason for time-delay fuses is to allow motor
starting current, while still providing reasonable over-current
protection. With a time delay fuse, you use a fuse that is 175% of
the motor full load rating. with a non time-delay fuse, you normally
need a fuse rated at 300% of the full load rating. So a time-delay
fuse is actually safer for things like motor loads. They are also a
good idea for any other loads that have a high startup current.

It has been a long while sence I have used fuse ratings, but I would
expect something like a NON for a non time delay and a FRN for a
time delay fuse. But I am not sure if that is an international
rating system. (I should know, but I have not needed this knowledge
in a long time.)


Black holes are where God divided by zero.

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