How would you adjust the brightness of a lightbulb?

Question

Suppose you wanted to be able to adjust the brightness of a light bulb in a lamp. Describe one way that you might be able to do this. If possible, don't recommend dimmers and light switches. Just describe what happens. (Grade 9 Physics)

If lowering the voltage is the answer, would it be possible? Or would I just have to get a bulb with a higher voltage?

Answer 1

You would use a rheostat, or potentiometer...which is what a dimmer switch is made out of. What a rheostat is, is an adjustable resistor. So as you turn, or slide, the control for the rheostat, you increase the resistance. With increased resistance, you are limiting the current, dimming the light bulb.

OK, V=(I)(R) This means that the current is directly proportional to the voltage, and inversely proportional to the resistance. So when the resistance increases, the current decrease...as does the voltage because they are proportional. So putting a resistor in line with the power to the light bulb will dim the bulb. Using a rheostat will enable you to adjust the amount of resistance, or how bright the bulb is burning.

Answer 2

A dimmer works by cutting off the electricity to the bulb for some fraction of the time, in little short pulses. For half brightness the power might be off for 1/240 of a second 120 times per second.

Another way is to lower the voltage.

Do not try either of these with fluorescent bulbs though, it will damage them.

Answer 3

The brightness of a lightbulb is determined by the size of its filament (wire that gets hot). The larger the filament the brighter the bulb's output.

http://www.howstuffworks.com/light-bulb.htm

Answer 4

"Just describe what happens..."

What happens is that the voltage is regulated or modified...
a method is found to lower the voltage, thus dimming the lightbulb.

Answer 5

you can't. A bulb has a certain wattage or Power. That can't be adjusted it is fixed.