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unknown asked in Science & MathematicsMathematics · 6 years ago

Math problem?

In electronics, power is equal to the square of the voltage divide by the resistance of a circuit.If the power is equal to 7,which of these resistances will yield a rational-number voltage 7,14,63,4,28?

PLEASE EXPLAIN

2 Answers

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  • ?
    Lv 7
    6 years ago

    v = sqrt(pr) = sqrt(7r)

    For a rational sqrt r/7 must yield a perfect square

    7/7 = 1 OK

    14/7 = 2 not OK

    63/7 = 9 OK

    4/7 not OK

    28/7 = 4 OK

    Answer 7, 63 and 28

  • ?
    Lv 7
    6 years ago

    p=v^2/r

    v^2=pr

    7,14,63,4,28

    y n y n y

    7x1 7x2 7x9 2x2 7x4

    Needs to be 7q where q is a perfect square.

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