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In a particular R-L series circuit a voltage of 10V at 50 Hz produces a current of 700mA while the samevoltage at 75 Hz produces 500 mA. What are the values of circuit constants? |
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Answer» (i) Z = √(R2 + (2π x 50L)2) = √(R2 + 98696L2); V = IZ or 10 = 700 x 10-3√(R2 + 98696L2) √(R2 + 98696L2) = 10/700 × 10−3 = 100/7 or R2 + 98696 L2 = 10000/49 ...(i) (ii) In the second case Z = √(R2 + (2π x 75L)2) = √(R2 + 222066L2) ∴ 10 = 500 x 10-3√(R2 + 222066L2) i.e √(R2 + 222066L2) = 20 or R2 + 222066L2 = 400 (ii) Subtracting Eq. (i) from (ii), we get 222066 L2 − 98696 L2 = 400 − (10000/49) or 123370 L2 = 196 or L = 0.0398 H = 40 mH. Substituting this value of L in Eq. (ii), we get, R2 + 222066 (0.398)2 = 400 ∴ R = 6.9 Ω |
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