Quick question. Bulbs in series circuit

[dantheman91]

Hello!

So i have a series circuit, say just 1.5v and i already have a bulb glowing. Let's say i add a bulb of similar resistance. I know the current will decrease because the overall resistance of of the circuit increases.

But do the bulbs both shine as bright as they did before? Or less bright/more bright? (i know they will be equally as bright since they have the same resistance)

Thanks!

 

[S_Happens]

What do you think will happen?

Hint: If you needed me to pick up that second light bulb for you, how would you describe it to me? Would you tell me the resistance of the bulb?

 

[dantheman91]

I think the bulbs will be dimmer because more resistance equals less current. The thing that confuses me is that if the resistance is raised in one of the bulbs, it will shine brighter. To me that goes against the more resistance = less current explanation. If the resistance in a bulb is raised, shouldn't the bulb shine less brightly? But it doesn't!

Also if the bulbs are in parallel circuit, the bulb with the lowest resistance will shine more brightly. hmm..

 

[S_Happens]

So why does less current mean anything?

If you stop making assumptions and answer my first question as well as this one, then you may just pull yourself out of the hole you seem to be stuck in.

 

[dantheman91]

I wasn't exactly sure what you meant in your question.

If i had to describe the bulb to you, and by pick up you mean go and get an identical bulb, i guess i would say "get me a 30 watt bulb"

Why does less current mean anything?

If there's less current, it means there's less power..

im sorry if i don't understand your hints, I am trying to understand this stuff better

 

[dantheman91]

But more resistance also means more voltage, which also means more power

 

[S_Happens]

If i had to describe the bulb to you, and by pick up you mean go and get an identical bulb, i guess i would say "get me a 30 watt bulb"

Why does less current mean anything?

If there's less current, it means there's less power..

Precisely. I was wanting you to think about power. Since you're considering identical bulbs, you can use it. Specifically, how can we determine power in this case?

But more resistance also means more voltage, which also means more power

Just because you have an equation relating voltage, current, and resistance does not mean you can create something from nothing. What is your voltage source and why do you think it can suddenly increase/decrease? You yourself stipulated the 1.5v.

You're not very far off, you just start thinking about one variable and lose sight of the whole picture. As I said, just because you know V = IR, does not mean that every single one is variable at any given time. In this case, you do know the voltage and you can assign arbitrary amounts for the resistances of the bulbs. This tells you what the current through the circuit does (larger, smaller, same). At that point, you know everything about the circuit and can see what the differences are in terms of power.

Sorry if it seemed like I was only answering your questions with questions. It seemed like it wouldn't take much to spur you in the right direction. If you appeared to not know anything, then I would have probably just stated information.

 

[dantheman91]

No thanks for asking the questions, it made me think.

I've run into another issue. I'm reading my textbook, which says:

"Although tungsten is an effective filament, when it is hot the tungsten vaporizes and the filament becomes thinner. This increases its resistance, which means it shines less brightly. Eventually, when it “burns out”, it becomes so thin and brittle that it ruptures."

In this case I'm confused. In a series circuit if you replace a bulb with a higher resistance bulb, it will shine more brightly. Not get dimmer.

From observations, when a bulb burns out, it flashes extremely brightly before going out.

Any hints on this one?

 

[Alex James]

Pace a switch between the battery and anyone of the connecting leads -preferably the one that connects to the positive of the battery, as a standard practicee.
______________________
http://www.kindsofcats.org/abyssinian-cats-colors/

 

[dantheman91]

I'm not sure that helps

 

[rcgldr]

A higher resistance bulb consumes less wattage and is dimmer, and a lower resistance bulb comsumes more wattage and is brighter, assuming the same filmament material, and same amount of voltage. If you put 2 bulbs in series, then that doubles the total resistance, cuts the effective voltage at each bulb in half, and the bulbs will be dimmer.

For example, in a strand of 50 small lights in series connected to a 120 volt source, each bulb gets 2.4 volts.

A link with some general info:

http://michaelbluejay.com/batteries/dc-christmas-lights.html

 

[janger]

In this case I'm confused. In a series circuit if you replace a bulb with a higher resistance bulb, it will shine more brightly. Not get dimmer.

From observations, when a bulb burns out, it flashes extremely brightly before going out.

Any hints on this one?

I think the textbook is saying: "up till the point before the filament ruptures, it burns less brightly."

Not totally certain on this but:
When the tungsten gets too thin at a spot, it breaks. This may cause an electric arc between the two pieces. Arcs are hot, bright, and hugely conductive. The larger current plus the heat melts more tungsten, which creates a larger arc, which conducts more current and creates more heat and light, melts more tungsten, making a bigger arc...rinse and repeat until either the gap can't keep the arc going, or the filament is totally burnt up, or the thin wires connecting the filament burn out from the huge current.