# ac electric math help

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**ac electric math help**

i cant read my formula in my notes on how to do this problem here is the problem

the peak voltage of a sine wave is 10v. what is its instantaneous value at 30 degrees and at 40 degrees?

anyone?

the peak voltage of a sine wave is 10v. what is its instantaneous value at 30 degrees and at 40 degrees?

anyone?

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**Re: ac electric math help**

Originally Posted by

**L27Buick**i cant read my formula in my notes on how to do this problem here is the problem

the peak voltage of a sine wave is 10v. what is its instantaneous value at 30 degrees and at 40 degrees?

anyone?

the peak voltage of a sine wave is 10v. what is its instantaneous value at 30 degrees and at 40 degrees?

anyone?

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**Re: ac electric math help**

Originally Posted by

**L27Buick**the peak voltage of a sine wave is 10v. what is its instantaneous value at 30 degrees and at 40 degrees?

anyone?

At 0, 180 and 360, your instantaneous voltage is 0, right?

At 90° you're 10v peak (assuming 20v p-p?), so at 30° you should be .3 of 10, or 3v. 40° would be 4v. Actually a pretty simple problem.

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**Re: ac electric math help**

Originally Posted by

**willwren**
Originally Posted by

**L27Buick**the peak voltage of a sine wave is 10v. what is its instantaneous value at 30 degrees and at 40 degrees?

anyone?

At 0, 180 and 360, your instantaneous voltage is 0, right?

At 90° you're 10v peak (assuming 20v p-p?), so at 30° you should be .3 of 10, or 3v. 40° would be 4v. Actually a pretty simple problem.

You have to know the cycle time to know the phase angle. The top (or bottom) of a sine wave is a parabola based on the amplitude and half-cycle time, therefor it is not a linear relationship for amplitude vs. angle.

Yes, I realize I am telling everything but how to find the answer. I would have to look it up either in a AC circuits or a trig textbook.

Jay