I know that when you get a current from a voltage (like calculating current through resistor), the current and voltage equations have the same frequency. Does this still hold for power P = VI ?(adsbygoogle = window.adsbygoogle || []).push({});

So assume V in Euler form, V(t) = Vcos(wt+theta) + jVsin(wt+theta) = V*e^{j(wt+theta)}and in Phasor, V<theta = Vcos(wt+theta)

And assume I in Euler form, I(t) = Icos(wt+phi) + jIsin(wt+phi) = I*e^{j(wt+phi)}and in Phasor, I<phi = Icos(wt+phi)

Then P = V(t)*I(t) = V*e^{j(wt+theta)}* I*e^{j(wt+phi)}

To get P = VI*e^{jwt+jwt+jphi+jtheta}, call jphi + jtheta = jpsi

Then P = VI *e^{2jwt+jpsi}

Then P = VI *e^{j(2wt+psi)}

Then P = VIcos(2wt+psi)+jVIsin(wt+psi)

Real component is what we want, so P = VIcos(2wt+psi)

2wt (power frequency) isn't the same as wt (the frequency of current and voltage). Did I get the right result?

**Physics Forums - The Fusion of Science and Community**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Do we get 2x the frequency when doing P=VI for AC Circuits?

Loading...

Similar Threads - frequency doing P=VI | Date |
---|---|

Resonance -- why do we calculate the frequencies w1 & w2 at half power frequencies? | Mar 10, 2016 |

How do you multiply the frequency of an oscillator? | Jan 1, 2013 |

Why do you get sideband frequencies for amplitude modulation (AM)? | May 15, 2012 |

How do electronics generate frequencies/signals ? | Jan 1, 2012 |

Do Fleming valves fail at high frequencies? | May 17, 2010 |

**Physics Forums - The Fusion of Science and Community**