Spring 11 Phys 121 - HW 14

# Spring 11 Phys 121 - HW 14 - dzifanu(sd26397 hw 14...

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dzifanu (sd26397) – hw 14 – opyrchal – (121102) 1 This print-out should have 11 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001(part1of3)10.0points In a certain RLC circuit, the rms current is 8 . 8 A, the rms voltage is 139 V, and the current leads the voltage by 69 . 2 . What is the total resistance of the circuit? Correct answer: 5 . 60907 Ω. Explanation: Let : I rms = 8 . 8 A , V rms = 139 V , and φ = - 69 . 2 . Z = V rms I rms = 139 V 8 . 8 A = 15 . 7955 Ω , and R = Z cos φ = (15 . 7955 Ω) cos( - 69 . 2 ) = 5 . 60907 Ω . 002(part2of3)10.0points Calculate the total reactance, X L - X C . Correct answer: - 14 . 766 Ω. Explanation: From tan φ = X L - X C R , we find X L - X C = R tan φ = (5 . 60907 Ω) tan( - 69 . 2 ) = - 14 . 766 Ω . 003(part3of3)10.0points Find the average power dissipated in the cir- cuit. Correct answer: 434 . 366 W. Explanation: P = I rms V rms cos φ = (8 . 8 A) (139 V) cos( - 69 . 2 ) = 434 . 366 W . AlternateSolution: P = I 2 rms R = (8 . 8 A) 2 (5 . 60907 Ω) = 434 . 366 W . 004(part1of3)10.0points A coil can be considered to be a resistance of 70 Ω and an inductance of 0 . 5 H in series.

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