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# line voltage

#### duke37

Jan 9, 2011
5,364
why we multiply with root 2??
A sine wave varies its voltage up and down. The voltage of the supply is quoted as the same as would produce the same average power as DC in a resistor. This calculated as the root mean square (RMS). It follows that at some times the voltage will be above the RMS and at other times it will be below. A sine wave will have a peak voltage of the RMS * root 2 and an average voltage of 0.9 of the RMS.

You can prove these relationships with calculus. Note that LTspice uses the peak voltage in their simulations.

#### RRITESH

Oct 10, 2010
85
What is difference between Sin trigonometric and sin wave?
SinQ=Perpendicular/hypertonus.

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
The trigonometric sin function is (as you say) opposite over hypotenuse (I prefer opposite to perpendicular as that os the correct mathematical term).

A sin wave is a wave where the absolute magnitude varies with time as the trigonometric function varies with angle. Indeed, you'll often see the the time axis marked in radians and phase relationships are measured in either radians or degrees.

#### RRITESH

Oct 10, 2010
85
Hello
what is absolute magnitude here?

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
what do each of those words mean?

can you future out what they mean together?

Oct 10, 2010
85
ok..

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