Mike
Carruthers:
Light bulbs it seems only blow out at the moment you turn them
on - why is that?
Ivan Semeniuk:
Electrical resistance is related to temperature - so the lower
the temperature the less resistance. And if the temperature
goes up, the more electrical resistance there is in a wire.
Ivan Semeniuk,
one of the authors of the book Why
Don't Penguins Feet Freeze?…
So, the filament
of the light bulb, when it's cold, (when it's been off for a
while), is when the resistance to electricity is the least.
So, at the moment you flip it on, that's when the highest current
can go surging through; it's that surge of current at the very
beginning that if there's a weakness in the filament, it'll
break at that point.
Ever wonder why
a whip cracks when you snap it? It's all physics, says Ivan.
When you snap the whip…
you sort of have
the heavy end of the whip transmitting its energy to the lighter
end of the whip and it's essentially because there's less mass
at the thinner end of the whip. The energy is turning into velocity
and you get to the point where at the very, very tip of the
whip there's a mini-sonic boom going on - it's actually breaking
the sound barrier.
And why don't
penguin's feet freeze?
Penguins - you
know they have to go marching out there on the ice and snow.
And the way they do it is with a very highly adaptive circulation
system to their feet - very small blood vessels, very rapid
circulation flow, which minimizes the heat loss keeping the
blood flowing through the feet very efficiently.
Tomorrow, why
ships have portholes - I'm Mike Carruthers and that's Something
You Should Know.
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