An electricity and magnetism problem by Rishabh Deep Singh

Find the RMS value of V s Vs to the truncated nearest integer.

Clarification i = 1 i= \sqrt{-1} .


The answer is 123.

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1 solution

Steven Chase
Jan 26, 2017

This is a cool problem. It relies heavily on complex power analysis principles, the full scope of which is too large to cover here. The biggest things to consider are the following:

1) The complex power (active power (P) + j * reactive power (Q)) through a load, as a function of the voltage and current through it is:

S = P + j Q = V I \vec{S} = P + jQ = \vec{V} \vec{I}^*

Where I \vec{I}^* is the complex conjugate of I \vec{I}

2) A load with leading power factor (capacitive) behaves as a reactive power source, and thus it consumes negative reactive power.

3) A load with lagging power factor (inductive) behaves as a reactive power sink, and thus it consumes positive reactive power.

Here is a sketch of my solution (programmed in Mathcad). I think the problem should state more clearly that it is looking for the RMS magnitude of the source voltage, truncated to the nearest integer (which turns out to be 123). @Rishabh Deep Singh , can you make this more clear?

Sir i have edited the Problem can you check it?

i have more problems of these kind, i will post them too.

Rishabh Deep Singh - 4 years, 4 months ago

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Can you mention that it should be truncated rather than rounded?

Steven Chase - 4 years, 4 months ago

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can you check, i just edited it

Rishabh Deep Singh - 4 years, 4 months ago

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@Rishabh Deep Singh Looks good. Thanks

Steven Chase - 4 years, 4 months ago

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