Calculating "theta" Using Step Up Transformer

[Carolyn]

Hi, so I know that VI = P cos (theta), but during an experiment using a step up transformer,

I got the primary voltage 7.42V, primary current 0.41A, and primary power 3.2W. How then should I calculate the angle theta. I can't use arcosine, 'cause that will give me undefined.

Thanks a lot.

 

[Pumblechook]

Doesn't sound right. You have Power in Watts (3.2) higher than the VA figure (3.042)

And P = VI x Cos phi

 

[Redbelly98]

How are you measuring the power? And the voltage and current, for that matter?

As Pumblechook said, P should be less than or equal to V*I=3.04 VA