# Appliance Voltage Specs

Q:
Too much information. My new refrigerator has a tag that warns "15 amps and 120 volts." It seems only one number would have sufficed -- in fact two numbers may conflict each other; here is why: Since R is constant (Rconstant), in the factory's design-and-development they jack up I until, due to Power = Imax*Rconstant^2, the wire fries. This sets Imax -- say 15 amps. The tag specifies "Plug into a circuit with breaker rated at Imax (=15 amps)." All set without needing Vmax. In other words Vmax = Rconstant * Imax. You do not need to specify Vmax since it results in an over-determined equation. I see the same on light bulbs -- bulbs also tell you wattage, but I guess it is to let you know (the fact of) power consumption, not a requirement. So why does the tag specifies V in addition to I?
- Mehran (age 65)
Miami
A:

Different countries (and outlet types) have different standard voltages. If you plug a device designed for 120V into a 220V supply, it will probably be destroyed even if the net current draw is limited by a fuse. The appliance may have semiconducting devices that don't draw much current but are easily fried.

Mike W.

(published on 10/11/2016)

## Follow-Up #1: frying circuits

Q:
How does 220V fry the semiconductor of 120V-rated device if it draws only the rated amperage (for the semiconductor part as well as the other parts of the device)? In other words, what are other modes of destruction / malfunction except for R*I^2 which is governed by I (and not V)? Why do simple incandescent light bulbs which do not have semiconductors have the two specs of amperage and voltage (in addition to power spec which is to inform the consumer of the energy consumption \$)?
- Mehran (age 65)
Miami
A:

It takes only a small current to fry the delicate control parts of a device.

Mike W.

(published on 10/24/2016)

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