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Unformatted text preview: Version One Homework 9 Savrasov 39819 May 15, 2006 1 This print-out should have 12 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. The due time is Central time. Changing Magnetic Field 31:01, trigonometry, numeric, > 1 min, nor- mal. 001 (part 1 of 1) 1 points A coil is wrapped with 300 turns of wire on the perimeter of a circular frame (of radius 80 cm). Each turn has the same area, equal to that of the frame. A uniform magnetic field is directed perpendicular to the plane of the coil. This field changes at a constant rate from 20 mT to 50 mT in 20 ms. What is the magnitude of the induced E in the coil at the instant the magnetic field has a magnitude of 35 mT? Correct answer: 904 . 779 V. Explanation: Basic Concepts: E =- N d B dt B Z ~ B d ~ A = B A Solution: E =- N d B dt =- N A B t =- N r 2 ( B 2- B 1 ) t =- (300) (80 cm) 2 (50 mT)- (20 mT) 20 ms =- 904 . 779 V |E| = 904 . 779 V . Induced EMF in a Coil 31:01, calculus, numeric, > 1 min, normal. 002 (part 1 of 1) 1 points A 30 turns circular coil with a radius 4 cm and a resistance 1 is placed in a magnetic field directed perpendicular to the plane of the coil. The magnitude of the magnetic field varies in time according to the expression B = a 1 t + a 2 t 2 , where a 1 = 0 . 01 T / s, a 2 = 0 . 04 T / s 2 are constants, time t is in seconds and field B is in Tesla. Calculate the magnitude of the induced E in the coil at t = 5 s. Correct answer: 0 . 0618265 V. Explanation: Basic Concepts: Faradays Law of Induc- tion E =- d B dt Note: The resistance of the coil is unnecessary when calculating the induced E . The area of the circular coil is: A = r 2 = (0 . 04 m) 2 = 0...
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This note was uploaded on 03/24/2011 for the course PHYS 13843 taught by Professor Dr.andygavrin during the Spring '10 term at IUPUI.
- Spring '10