Have you heard of rated voltage? Do you know what that is?

I read the rated voltage on a product specification.

Does that mean the product can only be used under the amount of voltage of the rated voltage? I am guessing.

There is probably some safety margin built into that rating, but yes... Using something at a voltage higher than its rating is dangerous, and likely to damage the equipment, start fires, or even injure/kill people.

depend on equipment.

for most equipments, it mean the nominal voltage at which the equipment is designed to operate to provide the rated performance. most equipments can operate at 5% or 10% above or below the rated voltage without much change in performance.

for wire, plug, socket, fuse or circuit breaker, it mean the maximum voltage that the type of wire, plug, socket, fuse or circuit breaker is designed for. in this case, the rated voltage is considerably higher than the nominal voltage.

now what is nominal voltage? again, depend on equipment.

for most equipments, it is the rated voltage that was written on it (at least written or your equipment).

for wire, plug, socket, fuse or circuit breaker, it mean the nominal (or rated) voltage of the equipment that the wire, plug, socket, fuse or circuit breaker is used on.

ok, i know that in lucky number slevin josh hartnett said don't use the word you're defining in the definition, so you can also describe nominal voltage as "standard value" that is, if it use 2 AA batteries then the standard value is 3V, or if you are in UK and using a household equipment, the standard value is 220 volts, the actual voltage might be 5 or 10% higher or lower.

one more thing, RMS value of an AC voltage is the effective value . it is the value that is usually stated when refering to an AC voltage. RMS stands for root mean square (or resistor power dissipation ratings according to Dennise). RMS is calculated by calculating the square root of the average of the instantanious voltages making up one cycle of the waveform. it can be calculated or measured for any waveform including square waveforms and distorted sine waveforms. for an undistorted sine wave, the RMS voltage is the peak voltage divided by the square root of 2.

so what about RMS value? nominal (rated) AC voltages are usually RMS values.

Every electric device has its own rated voltage.

For instance my handy's rated voltage is 3.3 volts.