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Electrical question - RMS value - Ur attention please!?

Staying away from Yahoo! Answers - 2008-05-13 15:27:29 - Engineering

In a DC system, if u are given the potential at two points to be equal, say 220 V, u can well be sure that no current can flow between them ie., we wont experience a shock if we touch these points each in one hand (of course, without being grounded). But is this true for AC? Given two points are each at 220 V, it is clearly the rms value. One voltage wave may be at its positive peak and the other at the negative one. So, wont the current become [220- (-220)] / R ? (R is the resistance of our body). Under the above context, isn't the concept of RMS value misleading the physical reality??

Най-добър отговор:

For a.c. you need to take the phase into account. RMS is useful for power calculations. If you apply 220V rms a.c. to a resistor, it will dissipate exactly the same power as if you apply 220V d.c., i.e. both will produce heat at the same rate. Use of RMS values in other contexts may be misleading, as you suggest.

Други отговори:

For a.c. you need to take the phase into account. RMS is useful for power calculations. If you apply 220V rms a.c. to a resistor, it will dissipate exactly the same power as if you apply 220V d.c., i.e. both will produce heat at the same rate. Use of RMS values in other contexts may be misleading, as you suggest.

No, RMS is the equivalent heating power of an AC waveform. It says nothing about phase or peaks. It is all it says it is, but no more. It is heating equivalent and that's all. And yes, the voltage between two AC waveforms of the same voltage but different phase can be as high as twice either one. And if you touch two points with 200 volts DC on them, one positive, one negative, you will get a shock of 400 volts. Same thing.