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31 July, 07:09

The power in an electric circuit varies inversely with the resistance. If the power is 2,200watts when the resistance is 25 ohms, find the resistance when the power is 1,100watts.

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Answers (2)
  1. 31 July, 07:41
    0
    50 ohms

    Explanation:

    From Electricity,

    P ∝ 1/R

    PR = k

    P'R' = PR ... Equation 1

    Where P' = Initial power, R' = Initial resistance, P = Final power, R = Final resistance

    Make R the subject of the equation

    R = P'R'/P ... Equation 2

    Given: P' = 2200 watts, P = 1100 watts, R' = 25 ohms

    Substitute into equation 2

    R = 2200 (25) / 1100

    R = 50 ohms
  2. 31 July, 10:04
    0
    50ohms

    Explanation:

    If the power in an electric circuit varies inversely with the resistance, it can expressed as P = k/R where;

    P is the power, R is the resistance and k is the constant of proportionality.

    From the formula, k = PR

    k = P1R1 = P2R2 ... (1)

    Given P1 = 2200watts, R1 = 25ohms, P2 = 1100watts R2 = ?

    From equation (1);

    R2 = P1R1/P2

    R2 = 2200*25/1100

    R2 = 50ohms

    The resistance when the power is 1100watts is 50ohms.

    This shows that as the power is decreasing, the resistance is increasing.
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