# HW 23 - benavides(jjb2356 – homework 23 – Turner...

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Unformatted text preview: benavides (jjb2356) – homework 23 – Turner – (59130) 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 10.0 points An air-core solenoid has a length of 73 . 3 cm, a cross-sectional area of 0 . 0687 m 2 , and contains 889 turns. The current through the solenoid increases by 9 . 58 A. The permeability of free space is 1 . 25664 × 10- 6 N / A 2 . By how much does the magnetic flux through the solenoid change? Correct answer: 1003 . 07 μ Wb. Explanation: Let : ℓ = 73 . 3 cm = 0 . 733 m , A = 0 . 0687 m 2 , N = 889 turns , I = 9 . 58 A , and μ = 1 . 25664 × 10- 6 N / A 2 . The magnetic field inside the solenoid is B = μ nI = (1 . 25664 × 10- 6 N / A 2 ) × parenleftbigg 889 turns . 733 m parenrightbigg (9 . 58 A) = 0 . 0146007 T . ΔΦ B = B A = (0 . 0146007 T) (0 . 0687 m 2 ) = 0 . 00100307 Wb = 1003 . 07 μ Wb . 002 (part 1 of 2) 10.0 points Two separate loops each with the same radius and a current, in the directions shown, whose centers lie on the same axis perpendicular to the plane of the loops. 24 cm radius 139A 139A 7 . 2 m This figure is not to scale. The loop radii are small com- pared to the distance between the loops. Note: The left-hand side of the circular loops are closer to you. What approximately is the magnetic flux enclosed by the left loop due to the current in the right loop. Correct answer: 2 . 43889 × 10- 9 Wb. Explanation: a radius I I ℓ Let : a = 24 cm , ℓ = 7 . 2 m , and I = 139 A . The magnitude of the magnetic field at the axis of a loop carrying a current I , if ℓ is much larger than a is given by B = μ 2 π μ ℓ 3 = μ I a 2 2 ℓ 3 = 2 π bracketleftBig μ 4 π bracketrightBig I a 2 ℓ 3 , where the magnetic dipole moment μ = I A = I π a 2 . The magnetic field at the left hand loop due to the right hand loop is nearly constant and parallel to the axis. Thus the magnetic flux from this field is benavides (jjb2356) – homework 23 – Turner – (59130)...
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## This note was uploaded on 03/26/2012 for the course PHY 303L taught by Professor Turner during the Spring '08 term at University of Texas.

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HW 23 - benavides(jjb2356 – homework 23 – Turner...

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