If we have equal Voltage and Resistance, which light bulb is brighter in a parallel system? in a series system? Are they equal in both cases?
2007-01-14 06:51:32 · 5 answers · asked by Anonymous in Science & Mathematics ➔ Physics
Here is the complete question:
2 Light bulbs, one of Resistance R1 annd the other of resistance R2, are connected to a battery (a) in parallel and (b) in series. Which bulb is brighter in each case if R1 = R2?
2007-01-14 06:56:03 · update #1
The book answer is (a) bulb 2 (b) bulb 1
I don't understand how they are not all equal.
2007-01-14 06:57:57 · update #2
JJ, hehe. Yes it does. But it as as a second part, so I though the answer was talking about R1=R2. It continues to ask "How is your answer different if R1>R2". Thanks!
2007-01-14 07:10:42 · update #3
The resistance of 2 bulbs in series would be the sum, as in 2R. The resistance of the same bulbs in parallel on the other hand is 1/(1/R+1/R), or (1/2)R, which is lower than 2R. Thus, more current will flow (I = V/R), and that means more energy output, and brighter bulbs. This is why most xmas lights are connected in parallel, not series.
Addendum: If the bulbs are the same, R1 = R2, how can it make a difference between the bulbs? Why should one burn brighter than the other in any case?
2007-01-14 07:01:52 · answer #1 · answered by Scythian1950 7 · 0⤊ 0⤋
It has to do with Voltage drop due to the Resistance, which would determine how much wattage you were getting at the end of the circuit.
Wattage = Voltage x Amperage
Voltage = Amperage x Resistance (V = I x R)
In a parallel system, each bulb is on it's own "leg". Therefore, each has the same voltage drop due to resistance of the bulb.
In a series system, both bulbs are on the same "leg", therefore the resistance is that which comes before the bulb itself plus all resistance before it. Hence, the 2nd bulb would get a sum total of it's own resistance plus the resistance of the 1st bulb.
Use this website, it has your experiment spelled out:
http://en.wikipedia.org/wiki/Series_and_parallel_circuits
2007-01-14 07:26:03 · answer #2 · answered by Goyo 6 · 0⤊ 0⤋
If they are itdentical bulbs, in parallel with the same amperage draw and same voltage drop, I would expect the illumination to also be the same.
(Now if they are different bulbs, even with the same resistance, there could be differences.)
2007-01-14 06:59:11 · answer #3 · answered by Anonymous · 0⤊ 0⤋
Wattage (i.e. power). Although some types are more luminous for a given wattage.
2007-01-14 06:53:28 · answer #4 · answered by gebobs 6 · 0⤊ 0⤋
Are you sure the question didn't say "R1 > R2" rather than "R1 = R2"?
2007-01-14 07:05:24 · answer #5 · answered by JJ 7 · 1⤊ 0⤋