Any real switch has some resistance which under enough current will burn it out. But the greatest threats to switches happen when they are opened and closed. When they are closed, inrush currents are many times the steady state current. The worst stress on switches is when they opened. Most circuits have some inductance, which will generate what ever voltage is required to maintain the current for some brief period. It may be only a millisecond but for that time the switch must dissipate the full circuit power. Power distribution breaker switches use compressed air to break the arc that happens when they open.



http://en.wikipedia.org/wiki/Circuit_bre...



Safety protocol requires the user to stand beside a highpower switch box when it is operated so that if an electrical explosion results, it will not blast directly into the user.



http://en.wikipedia.org/wiki/Arc_flash

These ratings are what the manufacturer has tested the equipment to handle safely. Usually the actual capacity is much higher but the manufacturer is covering their legal ***-ets. If you install the switch in a higher rated circuit and your house burns down, you won't be able to sue them for faulty equipment.

I hate it when manufacturers put ratings on their equipment. I really like unmarked equipment. It is much more exciting when I guess the rating and get it wrong. All those sparks and flames can really be something.

The question was so juvenile that I assumed it was a troll.

To avoid switch burns out if use it under its maximum current rate.

Over loading will cause fire and safety hazard.

So it is essential to use the proper range for your needs.

duh... so you know what the max voltage and current you can switch with them.