You have two incandescent lightbulbs, both labelled with 100W. One is made for t

Question

You have two incandescent lightbulbs, both labelled with 100W. One is made for the U.S. (110V), one for Europe (230V). What happens if you

a) Operate the Euro lightbulb in the U.S.?
b) Operate the U.S. lightbulb in Europe?
c) For metals (like the metal filament inside the bulb) the resistance typically increasewith temperature. Use this info to briefly discuss at which time (e.g. directly after switching on, after 1s or after a long time reaching a stable equilibrium) the U.S. bulb draws the highest current and the highest power from the outlet.

d) Your room is illuminated with incandescent lightbulbs. Now you switch on another appliance, e.g. a vacuum cleaner or a flat iron. Why are the lights going for a very brief moment a bit darker, when you switch on the other appliance?

Explanation / Answer

A)The amount of light given by an incandescent light bulb depends upon the temperature of the filament. This temperature depends upon the resistance of the filament and Ohm's Law (V= I*R) where V is the applied voltage, I is the current in amperes and R is the resistance of the filament in Ohms. Now a given wattage bulb rated for 220 volts has a filament that has a resistance which depends upon the metal type (usually tungsten), its length (usually they are wound like a spring but not always), the diameter of the filament (actually its cross sectional area) and the temperature of the filament. If the voltage is only 110 volts the temperature of the filament will be substantially lower than the same filament carrying a voltage load of 220 volts. Consequently, less light is given off but the life of the filament is longer because it is at a lower temperature. You can see an analogous effect in a flashlight when the batteries start to die. The light gets dimmer because less current is produced by the battery due to its loss in voltage.

B) the bulb's life is reduced and will shine brighter than in U.S. it can also fuse due to overpower.

C) it will take long time to completely glow as temperatue increase will take a gradual time material being matter.

But it will glow to optimistic conditions from the start.

D) there is an increase in load over the given voltage thereby producing a lag for te system to stabalise after some time being very mall.

Related Questions

Navigate

• Browse (All)
• Browse Y
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.