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Would really appreciate some help with this physics question

Hello there, I was just wondering.

Why is it that, if you connected 3 bulbs in series, 60 watt, 60 watt and 10 watt.

Why would the 10 watt have the most voltage

Why would the 10 watt have the most resistance

I keep thinking about P=V^2/R and P=(I^2)R

and then I can see how this works exactly.

thanks!

Reply 1

sulexk

can anyone help with this please

thanks!

Reply 2

Stonebridge

If they are in series (and are designed to operate in series) they all must have the same current.
P=VI
V=P/I
which means that the 10W bulb should have the least voltage
and as R=V/I it also means it will have the least resistance.
Where do you get the idea that it should be the highest value of V and R?
However, I suspect this is part of a longer question where these bulbs have been connected in parallel, maybe? Or where their voltage rating has been given.
In which case, your question is only half of the problem.
In order to answer it fully, you need to say what voltage rating the bulbs have for full power operation.
If they all operate at the same voltage for nominal power, then the 10W bulb does have a higher resistance than the other two. So, it depends.
Maybe you could explain the full problem?

Reply 3

sulexk

I got it from here:

http://cipco.apogee.net/foe/fcsps.asp

any ideas?

Reply 4

Stonebridge

sulexk

I got it from here:

http://cipco.apogee.net/foe/fcsps.asp

any ideas?

As I suspected, there was more to this question than in your original post. What you neglected to say was that the 10W bulb, and the 60W bulbs, are all rated to operate at 120V.
Using P=V²/R, you can see R=V²/P
this means that, as all bulbs operate normally at 120V the one with the lower power (10W) has higher resistance.
If you then put the bulbs in series, they all have the same current, but the one with the higher resistance (10W) has a greater pd across it because V=IR.