Combination Circuit Question School

Carultch said:
It's an academic example. It wouldn't meet code to solve this just with the materials given.

The premise is that the room in question only has the 240V circuit. No information on whether this is center-grounded like we do in the US, or end-grounded like 220V thru 240V circuits are in most of the world.
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Like we always do, we made the question far more complicated than was its intent. The obvious answer they were going for is the series parallel arrangement with two lamps in series connected in parallel with the other two lamps in series. Every lamp gets 120V and if a lamp burns out, it and its series partner go out while the other pair stays lit.
 
ggunn said:
The obvious answer they were going for is the series parallel arrangement with two lamps in series connected in parallel with the other two lamps in series. Every lamp gets 120V and if a lamp burns out, it and its series partner go out while the other pair stays lit.
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Yeah, that's grade school electrical theory and the obvious answer for a school project or after the Apocalypse. Anyone who decorated their Christmas Tree with old series light strings knows that.

But in the real world, it's part carter multipoint switching and part places where the electrical infrastructure looks like this.
 
Joethemechanic said:
Yeah, that's grade school electrical theory and the obvious answer for a school project or after the Apocalypse. Anyone who decorated their Christmas Tree with old series light strings knows that.
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Before that the bulbs were 120V all in parallel, but that was a significant fire hazard. A friend of my parents was having a big holiday party where the tree caught fire; he grabbed it, ran out through the French doors with it, and threw it into the swimming pool.
 
ggunn said:
Before that the bulbs were 120V all in parallel, but that was a significant fire hazard. A friend of my parents was having a big holiday party where the tree caught fire; he grabbed it, ran out through the French doors with it, and threw it into the swimming pool.
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Was the tree still plugged in? Did it get electrocuted?
 
Carultch said:
... It wouldn't meet code to solve this just with the materials given.
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A customer comes to you and want's four 100w lights installed in a boiler room. There is only 240v available. There wouldn't be any materials specified and none were here. It's completely up to you to come up with how to do it and with what. You quote four LED high bay fixtures with installation. The farthest thing from my mind would be cobbling up some kind of series/parallel arrangement with regular 100w light bulbs. That would be DIY for sure.

If you want to learn how resistors work in series and parallel arrangements and the calculations use actual resistors, not something that exhibits resistance. If I saw that question on a test I would think it was a trick question.

-Hal
 
hbiss said:
A customer comes to you and want's four 100w lights installed in a boiler room. There is only 240v available. There wouldn't be any materials specified and none were here. It's completely up to you to come up with how to do it and with what. You quote four LED high bay fixtures with installation. The farthest thing from my mind would be cobbling up some kind of series/parallel arrangement with regular 100w light bulbs. That would be DIY for sure.

If you want to learn how resistors work in series and parallel arrangements and the calculations use actual resistors, not something that exhibits resistance. If I saw that question on a test I would think it was a trick question.

-Hal
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It wasn't a question on a test. It was a question in homework, and maybe a darn good one.
 
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