In the power formula p = E x I x cos theta, what is cos theta when the voltage and current are in phase?

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Multiple Choice

In the power formula p = E x I x cos theta, what is cos theta when the voltage and current are in phase?

Explanation:
When voltage and current are in phase, the phase angle between them is zero degrees. The cosine of zero degrees is 1, so cos theta = 1. In the power formula p = E × I × cos theta, plugging in 1 gives p = E × I. That means all the power is real power with no reactive portion, since there’s no phase difference between voltage and current. The cosine value 1 directly reflects this in-phase relationship.

When voltage and current are in phase, the phase angle between them is zero degrees. The cosine of zero degrees is 1, so cos theta = 1. In the power formula p = E × I × cos theta, plugging in 1 gives p = E × I. That means all the power is real power with no reactive portion, since there’s no phase difference between voltage and current. The cosine value 1 directly reflects this in-phase relationship.

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