# Homework Help: Identical bulbs, rank by brightness

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1. Apr 9, 2016

### kamhogo

1. The problem statement, all variables and given/known data
Which bulb(s) will have the higher light intensity?

2. Relevant equations
Resistors:
Connection in series: same current
Connection in parallel: same delta V

3. The attempt at a solution
A and C are in series. They'll be equally bright. B is not connected to the negative terminal of the battery. no current will pass through it. Hence A=B>C

2. Apr 9, 2016

3. Apr 9, 2016

4. Apr 9, 2016

huh ?

5. Apr 9, 2016

Incorrect??

6. Apr 9, 2016

### phinds

well, what do you mean by it? What it says to me is very literal, A equals B and either both are greater than C or at least B is greater than C. I don't see how you get that from what's going on. Do you mean something else?

7. Apr 9, 2016

### kamhogo

I mean that A and B are equally bright and that both are brighter than C

8. Apr 9, 2016

### phinds

Yes, that's what I thought. Is that really what's happening?

9. Apr 9, 2016

### kamhogo

Sorry, I was confused. I meant A=C>B. Also, is there any current passing through B at all?

10. Apr 9, 2016

### phinds

Yes, that makes sense.

what do you think?

11. Apr 9, 2016

### kamhogo

I think there's no current passing through B at all. My reasoning: why would the electrons go through path with a resistor that does not lead to the negative terminal of the battery when they have the choice to take a resistless (ideally) path that leads to the negative terminal of the battery.

12. Apr 10, 2016

### Staff: Mentor

I don't understand this. Can you explain?

13. Apr 10, 2016

### cnh1995

Your answer is correct. Have you studied what an "open circuit" is?

14. Apr 10, 2016

### kamhogo

Not yet, but I am curious. I'll look it up. Is it when there is a gap somewhere on the circuit so the current pass? What is it useful for?

15. Apr 10, 2016

### cnh1995

It is the technical term for a "gap" in the circuit, so current can't flow through it.
A circuit needs to be closed for the flow of current. Here, no current flows through bulb B since there's no closed path.