Practice HW 17 solution

Practice HW 17 solution - song (shs546) – Practice HW 17...

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Unformatted text preview: song (shs546) – Practice HW 17 Solutions – weathers – (22202) 1 This print-out should have 12 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 0.0 points Calculate the magnetic flux through a 330 turn, 6 . 15 mH coil when the current in the coil is 4 mA. Correct answer: 7 . 45455 × 10- 8 Wb. Explanation: Let : N = 330 , L = 6 . 15 mH = 0 . 00615 H , and I = 4 mA = 0 . 004 A . The inductance of a coil is related to the magnetic flux as L = N Φ I Φ = L I N = (0 . 00615 H) (0 . 004 A) 330 = 7 . 45455 × 10- 8 Wb . 002 0.0 points A small air-core solenoid has a length of 10 cm and a radius of 0 . 5 cm. The permeability of free space is 1 . 25664 × 10- 6 N / A 2 . If the inductance is to be 0 . 73 mH, how many turns per centimeter (whole turns plus fractional turns) are required? Correct answer: 86 . 0026 turns / cm. Explanation: Let : ℓ = 10 cm = 0 . 1 m , μ = 1 . 25664 × 10- 6 N / A 2 , r = 0 . 5 cm = 0 . 005 m , and L = 0 . 73 mH = 0 . 1 m . Let n be the number of turns per centimeter. The area is A = π r 2 = π (0 . 005 m) 2 = 7 . 85398 × 10- 5 m 2 . The inductance of the air-core solenoid is L = μ n 2 A ℓ n 2 = L μ A ℓ = 1 1 . 25664 × 10- 6 N / A 2 × . 00073 H (7 . 85398 × 10- 5 m 2 )(0 . 1 m) = 7 . 39645 × 10 7 (turns / m) 2 Therefore, n = radicalBig 7 . 39645 × 10 7 (turns / m) 2 = 8600 . 26 turns / m = 86 . 0026 turns / cm . 003 0.0 points A coil of wire of negligible resis- tance, acting as an inductor, is connected into a simple electrical circuit as shown. S core The voltage drop (or emf ) across the induc- tor depends on which of the following: A) the number of turns of wire in the coil B) the current flowing through it C) its capacitance D) how rapidly current is changing in the coil E) the charge accumulated in the coil song (shs546) – Practice HW 17 Solutions – weathers – (22202) 2...
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This note was uploaded on 04/22/2011 for the course PHYS 2220 taught by Professor Littler during the Spring '00 term at North Texas.

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Practice HW 17 solution - song (shs546) – Practice HW 17...

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