Hi
What is the problem or consequence when a circuit with wrong polarity is connected to lighting loads or equipment???
Thanks 
ken
Unexpected things happen. Some of them might be serious problems.
AC or DC ? (AC has no polarity so the question , as stated, makes no sense except to say nothing will happen if an AC light iis connected backwadrs ( N to LINE) .
"lighting loads" by itself, is incredibly vague given the variety of devices that emit photons so nothing can be said about that until you specify what kind of light. Incandescent lights have no polarity. LEDS are diodes which by nature do NOT conduct when connected backwards ( nothing would happen).
LED modules with integrated regulators must be connected correctly to avoid damage.
It would depend on what the circuit was and what the equipment was. Sometimes nothing. Sometimes destruction of IC's. Sometimes only partial destruction, and the equipment might seem to work, but damage was done. It's really a guessing game without knowing what the actual circuit with the wrong polarity was (signal/power), and what the equipment/lighting was, and what the symptoms are.
Recently I soldered an SMD tantalum cap in the wrong way. Luckily, the circuit was part mains (of course not the part containing the tantalum cap), so I was careful when tasting anyway, and the cap was on the bottom of the board, but it sounded like a little firecracker and a spark flew almost a meter over the floor from under the board.
ElCaron:
, so I was careful when tasting anyway,
Just curious...what does an exploding cap taste like anyhow????? Pop-rock candy??
tinman13kup:
Just curious...what does an exploding cap taste like anyhow????? Pop-rock candy??
...with nuances of copper?
Aly electrolytics make a loud crack and leave an acrid smell/(taste?)
Allan
What is the problem or consequence when a circuit with wrong polarity is connected to lighting loads or equipment???
Clarify exactly what you mean. Your vague question has resulted in a wild goose chase ...
The OP's question might mean, "what happens when I plug stuff into a receptacle whose neutral and hot connections are reversed?" If that's really what he's wondering about, here are a few consequences:
- Changing a screw-base lamp, without unplugging the luminaire, becomes dangerous, since the highly-accessible screw and socket would be energized, rather than the much less accessible button connection.
- Any device whose power switch only disconnects only the hot leg would remain energized when switched off, making it dangerous to a careless operator wielding a screwdriver.
- For a line-powered device made by a hobbyist - as many of the gizmos discussed here are - there's no telling.
The ultimate consequences will depend on the operator's caution, luck, the system voltage, and the working conditions. In 230V systems, maybe that's death. In 115V systems, common in the US, there's less death and more cursing. Naturally, if an operator gets a jolt while he's on a ladder, he'll usually wind up on the floor, with the usual consequences. Or, maybe everybody gets lucky, and nothing interesting ever happens.
If that's really the OP's question, I hope that he says so. We need to know what country and what voltage we're talking about.
I disagree. Three prong plugs are used when the neutral is connected to the chassis and the safetty comes frombthe fact that it is IMPOSSIBLE to connect it backwards. Two- prong plugs , on the other hand do not have neutral connected to the chassis. This is how all desk lamps are wired. All newer desk lamps have a KEYED plug which PREVENTS reverse polarity. The load itself doesn't cre which way you connect it. The whole safety issue is irrelevant because the wuestion was what hsppens TO THR LIGHTING LOADS, NOT what happens to the OPERATOR..
raschemmel:
Three prong plugs are used when the neutral is connected to the chassis ...
What's the value in that? If the hot and neutral conductors are reversed on the receptacle, then the chassis will be energized directly from the hot conductor. I know that was done with some radios and televisions in the previous century, but the scuttlebutt is that those devices are dangerous to work on. Does anybody still connect a any power conductor to anything that might be called a "chassis?"
I don't know the percentage of incorrectly-wired receptacles, but it's not trivial. The NEC requires proper wiring, but doesn't require verification. The Health Care Facilities Code, NFPA 99, requires 100% "polarity" testing of receptacles in patient care areas. I've reviewed a bunch of testing reports, and I've observed a bit of testing. That experience tells me that not every receptacle gets installed correctly on the first try. I don't expect that the error rate improves in less demanding facilities, where no testing will be performed, and I don't expect that many of those errors ever get fixed.
The whole safety issue is irrelevant because the wuestion was what hsppens TO THR LIGHTING LOADS, NOT what happens to the OPERATOR..
Everyone's noted that it's hard to tell exactly what the OP is asking about. But, I don't see anything in the question says that he's strictly asking about consequences to lighting or other loads. When the receptacle polarity is reversed - if that's in fact what he's asking - the system is less safe. As a guy who sometimes works on electrical stuff, I call that a consequence.
raschemmel:
I disagree. Three prong plugs are used when the neutral is connected to the chassis and the safetty comes frombthe fact that it is IMPOSSIBLE to connect it backwards.
In your country perhaps. Schuko is absolutely symmetric. There isn't even a rule what hole is what, and if there is, nobody follows it and it is not printed on the inside of the outlet.
In Europe safety regulations state that there must bee no compromise in safety if live and nutral are reversed. It is one of the rules any item must meet to get CE compliance.
Grumpy_Mike:
In Europe safety regulations state that there must bee no compromise in safety if live and nutral are reversed. It is one of the rules any item must meet to get CE compliance.
Not in the cases where CE stands for China Export 
It depends on the font and kerning.
Grumpy_Mike:
In Europe safety regulations state that there must bee no compromise in safety if live and neutral are reversed. It is one of the rules any item must meet to get CE compliance.
That sounds like a reasonable rule for a residual current device (RCD), or, as we call it in the US, a ground-fault circuit interrupter (GFCI). How is a rule like that applied to to, say, a table lamp?
If anyone asks something where polarity is involved, it is assumed a DC circuit and not an AC circuit, since AC doesn't have polarity (i.e. "+" and "-")
Revering polarity on a circuit, with polarity protection could end up with burnt / blown capacitors, LED's, diodes, MCU's, etc.
There isn't even a rule what hole is what, and if there is, nobody follows it and it is not printed on the inside of the outlet.
In the USA the two prong plugs are keyed with the neutral prong wider than the Line prong and the sockets are similarly keyed. Two prong UL certified products do not have any connection from neutral to the metal body of the product.
What is the problem or consequence when a circuit with wrong polarity is connected to lighting loads or equipment???
Define "circuit"
Define "lighting loads"
raschemmel:
In the USA the two prong plugs are keyed with the neutral prong wider than the Line prong and the sockets are similarly keyed. Two prong UL certified products do not have any connection from neutral to the metal body of the product.
In good parts of Europe, they are not.
That sounds like a reasonable rule for a residual current device (RCD), or, as we call it in the US, a ground-fault circuit interrupter (GFCI). How is a rule like that applied to to, say, a table lamp?
There isn't really much to do about a table lamp, is there? You learn that you unplug the thing before changing the bulb, because the more exposed part of the socket may be exposed. If there are other metal parts exposed, they are connected to PE. In old installations without RCD, PE may be connected to neutral in the outlet, so a failure in the lamp would probably trigger the breaker. In any modern installation there is real PE and RCD.