Phys121-11sol

Phys121-11sol - Anderson, Matthew Homework 11 Due: Apr 15...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Anderson, Matthew Homework 11 Due: Apr 15 2008, 9:00 am Inst: Vitaly 1 This print-out should have 11 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. The due time is Central time. 001 (part 1 of 1) 15 points A plane loop of wire of area A is placed in a region where the magnetic field is perpendicu- lar to the plane. The magnitude of B varies in time according to the expression B = B e- at . That is, at t = 0 the field is B , and for t > 0, the field decreases exponentially in time. Find the induced emf, E , in the loop as a function of time. 1. E = aB t 2. E = aAB e- 2 at 3. E = aAB e- at correct 4. E = AB e- at 5. E = aB e- at 6. E = aAB Explanation: Basic Concepts: Faradays Law: E I E ds =- d B dt Solution: Since B is perpendicular to the plane of the loop, the magnetic flux through the loop at time t > 0 is B = B A = AB e- a t Also, since the coefficient AB and the pa- rameter a are constants, and Faradays Law says E =- d B dt the induced emf can be calculated the from Equation above: E =- d B dt =- AB d dt e- a t = aAB e- a t That is, the induced emf decays exponentially in time. Note: The maximum emf occurs at t = 0 , where E = aAB . B = B e- at B ~ t The plot of E versus t is similar to the B versus t curve shown in the figure above. keywords: 002 (part 1 of 1) 15 points The plane of a rectangular coil, 7 . 2 cm by 11 . 4 cm, is perpendicular to the direction of a uniform magnetic field B . If the coil has 38 turns and a total resistance of 11 . 1 , at what rate must the magnitude of B change to induce a current of 0 . 14 A in the windings of the coil? Correct answer: 4 . 9823 T / s. Explanation: Given : x = 7 . 2 cm = 0 . 072 m , y = 11 . 4 cm = 0 . 114 m , N = 38 turns , r = 11 . 1 , and I = 0 . 14 A . The induced emf is E = I R = N d dt = N d ( B A ) dt = N A dB dt , so dB dt = I R N ( xy ) = (0 . 14 A)(11 . 1 ) 38(0 . 072 m)(0 . 114 m) = 4 . 9823 T / s . Anderson, Matthew Homework 11 Due: Apr 15 2008, 9:00 am Inst: Vitaly 2 keywords: 003 (part 1 of 1) 15 points A conducting bar moves as shown near a long wire carrying a constant I = 30 A current. I a v L A B If a = 2 . 4 mm, L = 140 cm, and v = 26 m / s, what is the potential difference, V V A- V B ?...
View Full Document

This note was uploaded on 03/11/2010 for the course PHYS 121 taught by Professor Opyrchal during the Spring '08 term at NJIT.

Page1 / 6

Phys121-11sol - Anderson, Matthew Homework 11 Due: Apr 15...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online