sine wave

sine wave; you are using 230 volt/115 volts the peak voltage for 115 is 163 volts peak plus (+) and returns to zero & goes in other direction to a peak of 163 volts minus (-) in

.0166 seconds, your 230 volt is peak 326 volts, the D.C. 115 volt does not change direction, the 115 v D.C. equals the 115 v A.C. the same energy. perry

when we say the power at the house is 230v, 60hz

That means the Root Mean Square Power is 230V (and that goes for current too)

As you know the voltage goes from +ve to -ve in the sine manner in the AC power supply. Why ?

The frequency is 60Hz in your case. ie the voltage peaks to V_p 60 times and falls to -V_p 60 times in every second. and in between passes every sort of values.

If I talk about resistive circuit (simplest) then the power consumed is at any moment is V_t²/R.

But This value V_t vaies between ±V_p

To take care of the problem, (and assuming the electrical inertia of normal systems you integrate it over a cycle and then you get the value as

P = V_p²/2R

ie the effective voltage will be V_p/√2/

This Voltage (Root Mean Square - we have taken the square of the Voltage and averaged over a cycle and then taken square root ) is the effectively voltage that will be generating power as if it is a DC (constant voltage) source.

So the peak to peak power will be √2V_rms = √2 x 230 = 325.27 V

similar logic goes for current too.

So the voltage is neither between peak positive and negative nor between +ve and zero- it is the useful voltage.

The AC lines (unless it is multiphase), the neutral is grounded and the voltage in phase oscillates between + and -

In case of between 2 phases in a 3 phase supply, it is between + and - with ref to neutral

In case of DC one is usually + and other zero (earth) or (-ve) like in cells

.

In AC sine wave 230 volts 60 Hz the value is the RMS value.

Please read the following link for a clear knowledge of AC supply.

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