I just got new energy-saving bulbs in my bathroom but they\'re thehollywood styl

Question

I just got new energy-saving bulbs in my bathroom but they're thehollywood style (or "globe lamp"). I've noticed that when I turnthem on they're very dim, but get brighter over time. I know thatplugging multiple lightbulbs into a series set-up will make anylightbulb do this, but I also know that houses are wire inparallel.
In my physics class, we had an example shown to us where a 15 wattbulb and a 25 watt bulb were plugged into a series configuration,an the 15w was brighter due to the P=I^2 x R equation, where highpower is proportional to high resistance.

But this does not explain why lightbulbs in parallel would getbrighter over a period of time. Is it heat causing lowerresistance? I really don't know, but would like to so I can put theobservation in my Physics Journal.

Explanation / Answer

When two resistors are in a parallel combination.Bothresistors are connected directly across the terminals of thebattery.Therefore,the potential difference across the resistors arethe same: V = V1 = V2 where V is the terminal voltage of the battery. The power is P = V * I As the potential difference is constant for theresistors,therefore,the lightbulbs in parallel would get brighterover a period of time.Heat does not cause lower resistance,this isbecasue as the heat increases the resistance of the light bulbsincreases and hence the power consumed by the light bulbsincreases.

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