Which bulb will be brightest from three bulb connected in series with 100 volt dc?

- shamim

Which bulb will be brightest from three bulb connected in series with 100 volt dc?

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- shamim

I mean 3 bulbs r connected in series connection with 100 volt direct current

- shamim

Can u tell me which bulb will b brightest n why. Explain plz

- anonymous

if the bulbs are all equivalent, they have all the same electrical resistance, the brightness is the same for all of them, since the current is the same and the brightness should be a fraction of \(P=IR^2\).

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## More answers

- radar

Provide the information on the bulbs, if Identical, then heed Greg_D advice, or if resistance of the filament is given, heed the advice.

- shamim

All the 3 bulbs r same power

- shamim

For example each bulb has 60 watt

- shamim

I think each bulb has same resistance

- anonymous

if they are identical 60 watts bulb, then what i said before holds.
i think that is the case in this problem :)

- shamim

But according to my book of igcse , brightness will b different for each bulb

- shamim

I know current for each bulb will b same. Becase all the 3 bulbs r in series connection

- shamim

@radar

- anonymous

are you sure you are looking at the same situation in your book?
make sure they are not connected in parallel and that they are all equal.
I found this discussion in a forum online, reat it, as it may give you a better idea on how to think about the problem:
http://www.candlepowerforums.com/vb/showthread.php?281627-Lightbulbs-in-series-relative-brightness
hope it helps!

- anonymous

I have to disagree with @Greg_D on this one. If he ever connected a circuit like this he would see that what he asserts is not what actually takes place! In a series circuit, the brightness of the bulbs decreases, with the first bulb in the circuit being the brightest, and the last bulb in the circuit being the dimmest, even if they all have the same resistance. The reason for this is that the electric potential drops across each load, leaving a lower potential for the remaining loads in the circuit once the potential difference has dropped across the first one, and so on.

- shamim

Hw electric potential energy vary across bulbs? Explain more plz!!

- shamim

@ghuczek

- anonymous

If the three bulbs have the same resistance, they have equal voltage drops. The current flowing through each is the same. Each bulb consumes some of the available energy, so less is available further down the circuit. The bulbs get dimmer.
This is not the same as what happens in a parallel circuit, since the voltage drop across each of the bulbs is the same. Each will draw the same amount of energy. If one bulb burns out in a parallel circuit, the remaining bulbs will all burn a bit brighter, since the energy is being consumed over fewer bulbs, but they would still be equally bright.

- shamim

Thanl u very much @ghuczek

- IrishBoy123

i agree tots w/ @Greg_D but haven't got time to go into
@shamim
is it AC or DC? if DC, & is it the bulb closest to +ve or -ve terminal that is supposed to shine brightest? i am asking these questions in order to probe the book's conclusion.

- anonymous

i cannot deny what @ghuczek says, since i don't recall making that experiment, maybe in school, but i don't remember the results.
Now, if that is the case, then modelling the circuit using Ohm's law, and considering the brightness as a fraction of the dissipated energy, is not enough to reproduce that conclusion.
I would like to add that i don't think that the current can be reduced further down the circuit, because the number of electrons flowing per time unit will be the same, despite of the dissipation produced by the resistors.
Anyway, this is a good discussion, hope it results fruitful to everyone reading!

- radar

Which bulb is first lol. Conventional current I guess the bulb closest to the positive terminal or for the electron flow crowd the first bulb would be located next to the negative terminal. For AC source the first bulb would alternate between the two terminals. Don't you see how silly as to say the energy is getting less as it goes down the pike. True, the incandescent filament has resistance that will vary with temperature, but if the bulbs are rated at a wattage value, then when operated at their rated voltage and current, then the resistance will stabilize in its value.

- shamim

I think the first bulb frm negative pole will b brightest

- radar

@shamin I would like to see the reasoning why the bulb connected to the negative terminal would dissipate more power than the rest of the "identical" bulbs, please include the math for proof.

- shamim

Actually the fact is not clear to me! I need help!

- radar

Maybe it isn't a fact. It may be that the bulb that appears brighter is closer to the observer's eye, or their is some charateristic that is not identical to the other two bulbs. But it certainly is not a "fact."

- radar

So if it is not "clear" is not an indication that you don't understand the electrical facts, but that you do.

- Vincent-Lyon.Fr

@shamim
Since you say you have a book for igcse, please post full question and sketch, if any.
Identical bulbs in series will all glow the same, no question about that.

- anonymous

i agrre with @Vincent-Lyon.Fr , if you can, please post the problem statement and any solutions/suggestions given by the book, as literaly as possible.

- radar

@shamim
Answer number 4 on this link.
http://www.physicsclassroom.com/class/circuits/Lesson-4/Series-Circuits
Better yet, read it all and work the problems (answers are given) , but 4 is exactly this problem.

- shamim

Thanks a lot to all !!!!!!!!

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