# Switch not operating?

1. Homework Statement
A student finds that a set of Chrismas-tree lights do not operate when the switch is turned on. What is the most likely cause of this?

2. Homework Equations
none

3. The Attempt at a Solution
There could be a hole somewhere along the circuit.
There could have been a short circuit. But wouldn't that lead to an explosion of some sort?
The switch isn't working.
There could be many possibilities but don't know which is most likely.

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berkeman
Mentor
Keep in mind that Christmas tree lights are often a set of light bulbs wired in series. Does that help?

That would mean when one globe pops, the others will be brighter as the resistance is added but currect is same for all globes.

Or are you saying, when one pops, the current going into all the other globes will have increased and that is the problem. The globes will only work within a specific range of current and therefore potential difference since R in each globe is fixed?

Hootenanny
Staff Emeritus
Gold Member
The bulbs are in series, which means that a the circuit can be consider a single loop, passing through each of the bulbs. So, if one bulb blows, the circuit it broken and hence non of the other bulbs will work.

The bulbs are in series, which means that a the circuit can be consider a single loop, passing through each of the bulbs. So, if one bulb blows, the circuit it broken and hence non of the other bulbs will work.
Good one. I actually thought of it but thought it too unrealistic but if you think about it, it's true. If a bulb stops working, the only reason is that current has stopped flowing in its coil. When that happens, it means there is a connection failure and the rest of the bulbs stop receiving current.

berkeman
Mentor
Good one. I actually thought of it but thought it too unrealistic but if you think about it, it's true. If a bulb stops working, the only reason is that current has stopped flowing in its coil. When that happens, it means there is a connection failure and the rest of the bulbs stop receiving current.
Just to clarify the terminology a bit for you. The word "coil" is usually used for an inductor, where the inductance is being used for some purpose in the circuit. The part of a light bulb that glows when you put a current through it is called the "filament". Wouldn't want you to get that marked wrong on your report.

HallsofIvy