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Unformatted text preview: nanni (arn437) – HW #9 – Erskine – (56905) 1 This printout should have 15 questions. Multiplechoice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Would electromagnetic waves exist if chang ing magnetic fields could produce electric fields, but changing electric fields could not in turn produce magnetic fields? 1. Can’t be determined unless we know the propagation medium of the electromagnetic waves. 2. More information is needed. 3. Yes; electromagnetic waves consist of ei ther electric or magnetic fields, but not neces sary both. 4. Yes; only the magnetic field changes in electromagnetic waves. 5. Yes; as long as we have a magnet, there is a magnetic field to form the electromagnetic waves. 6. No; electric and magnetic fields coexist in electromagnetic waves by field induction. correct Explanation: Electric and magnetic fields coexist in elec tromagnetic waves by field induction. 002 (part 1 of 6) 10.0 points Which of Maxwell’s equations can be used, along with a symmetry argument, to calculate the electric field of a point charge? 1. contintegraldisplay vector B · d vector A = 0 2. contintegraldisplay vector B · d vector A = μ ǫ ∂ Φ E ∂t 3. contintegraldisplay vector B · d vector A = μ I 4. contintegraldisplay vector E · d vector A = Q ǫ correct 5. contintegraldisplay vector B · d vectors = μ I + μ ǫ ∂ Φ E ∂t 6. contintegraldisplay vector E · d vector A = − ∂ Φ B ∂t 7. contintegraldisplay vector B · d vectors = 0 8. contintegraldisplay vector E · d vectors = − ∂ Φ B ∂t 9. contintegraldisplay vector E · d vectors = Q ǫ 10. contintegraldisplay vector B · d vector A = Q ǫ Explanation: Maxwell equation, contintegraldisplay vector E · d vector A = Q ǫ , comes from Gauss’s Law and can be used to calculate the electric field of a point charge. contintegraldisplay vector E · d vector A = Q ǫ E contintegraldisplay d vector A = Q ǫ E (4 π r 2 ) = Q ǫ E = 1 4 π ǫ Q r 2 , where contintegraldisplay d vector A = 4 π r 2 is the surface area of a sphere of radius r . The equation is also known as Coulomb’s Law. 003 (part 2 of 6) 10.0 points Which of Maxwell’s equations can be used, along with a symmetry argument, to calcu late the magnetic field produced by a uniform timevarying electric field? 1. contintegraldisplay vector B · d vector A = Q ǫ 2. contintegraldisplay vector E · d vector A = − ∂ Φ B ∂t 3. contintegraldisplay vector B · d vectors = μ I + μ ǫ ∂ Φ E ∂t correct 4. contintegraldisplay vector B · d vector A = μ ǫ ∂ Φ E ∂t 5. contintegraldisplay vector B · d vector A = μ I nanni (arn437) – HW #9 – Erskine – (56905) 2 6....
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This note was uploaded on 11/02/2011 for the course PHYSICS 317L taught by Professor Erskine during the Fall '11 term at University of Texas.
 Fall '11
 ERSKINE

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