Physics: Principles and ProblemsChapter 22:
Current ElectricityProblem of the Week (0.0K) | Incandescence
Incandescence is the process of heating up an object so hot
that it gives off electromagnetic radiation in the visible region,
in other words, you heat it till it glows. | All
warm bodies emit electromagnetic radiation, from lightbulbs
to index fingers. (0.0K) | Lightbulbs
basically,
tungsten filamented, electricity-to-light/heat converters
(0.0K)
All lightbulbs have power ratings, for instance, 60 W. You have
learned that power depends upon current and voltage in the relation
P = IV. Because the wall voltage is a constant 120 volts, the
power must depend upon the current flowing through the bulb.
Current, in turn, depends upon the resistance of the lightbulb,
that is, the resistance of the tungsten wire. What might influence
the resistance of the tungsten wire? | (0.0K)
The
longer the wire, L, the more resistance. The larger the
wire, A, the less the resistance. Think of a pipe carrying
water, this relation R (0.0K) L/A
makes sense. Rho is a property of the metal, in this case, (0.0K) tungsten= 5.6 x 10-8 (0.0K)m.
| (0.0K) | In
150-W bulb, how long is the filament? Tungsten filament is drawn
to a radius of 45 microns (µm). |
How
might you pack a semi-truck long filament into a fist-sized
glass bulb? The solution, make a coil of the wire. If that coil
is still too long, coil the coil; and that is what is done,
a filament is a coiled coil. (0.0K) | (0.0K) | To
closely pack the filament wire, the coils are wound at 250 turns
per inch. In order to for the current to flow through the entire
wire, none of the coils can touch its nearest neighbor. What
is the space gap between each coil? | (0.0K) | (0.0K) | (0.0K) | (0.0K) | (0.0K) |
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