# power in out of phase circuits

#### paul_alan

Joined Nov 5, 2011
43
I'm just starting to work on power in AC CIrcuits. And i'm not understanding this question;
true or false: a current that leads a voltage source by 30° uses more power than a current that lags it's voltage source by 30°.

#### crutschow

Joined Mar 14, 2008
27,701
The question is simple. It's more likely the answer that you are having a problem with. So does a leading power factor of a given angle use more power than a lagging power factor? If you know the equation for calculating real power based upon the phase angle then you can determine the answer.

#### who_me_yes_you

Joined Dec 7, 2011
8
Real power = V*I*cos[angle between current and voltage]

considering the above equation, because the values of [cos 30] and [cos-30] are the same, then the amount of real power dissipated will be the same regardless of whether voltage leads or lags current.

(The phase angle relates to whether the circuit is capacitive or inductive in nature...)

#### crutschow

Joined Mar 14, 2008
27,701
Aw, you spoiled the fun and told him the answer. #### who_me_yes_you

Joined Dec 7, 2011
8
Sorry for being a spoil sport!

#### bountyhunter

Joined Sep 7, 2009
2,512
I'm just starting to work on power in AC CIrcuits. And i'm not understanding this question;
true or false: a current that leads a voltage source by 30° uses more power than a current that lags it's voltage source by 30°.
What kind of "power"?

There are actually three different types of "power" used commonly in electronics:

1) Watts (true power)

2) VA (Volt-Amps)

3) VARs (Volt-Amps Reactive)