HW02-solutions - Munoz (gm7794) – HW02 – TSOI –...

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Unformatted text preview: Munoz (gm7794) – HW02 – TSOI – (92515) 1 This print-out should have 16 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points The diagrams below depict three electric field patterns. Some of these patterns are physi- cally impossible. Assume these electric field patterns are due to static electric charges outside the regions shown. (a) (b) (c) Which electrostatic field patterns are phys- ically possible? 1. (b) and (c) 2. (a) and (c) 3. (a) and (b) 4. (a) only 5. (c) only 6. (b) only correct Explanation: Electrostatic lines of force do not intersect one another. Neither do they form a closed circuit (unless there is a changing magnetic field present). 002 10.0 points Given symmetrically placed rectangular insu- lators with uniformly charged distributions of equal magnitude as shown in the figure. x y + + + + + + + + + + + +- -- - - - In this figure, at the origin, the net field % E net is 1. zero and the direction is undefined. 2. along 30 ◦ direction in the first quadrant. 3. aligned with the positive x-axis. 4. aligned with the negative y-axis. correct 5. along 225 ◦ direction in the first quad- rant. 6. aligned with the negative x-axis. 7. along 60 ◦ direction in the first quadrant. 8. along 135 ◦ direction in the first quad- rant. 9. aligned with the positive y-axis. 10. along 45 ◦ direction in the first quadrant. Explanation: At the origin the fields from the bottom slab points towards the negative y axis (towards the negatively charged slab). The field from the right and left slabs have equal magnitudes at the origin and are sym- Munoz (gm7794) – HW02 – TSOI – (92515) 2 metric about the y axis. The field from the right and left slabs point away from each pos- itively charged slab. Therefore the x compo- nent of the field cancels at the origin. The net field from the right and left slabs points towards the negative y axis (away from the positively charged slab). Hence, the sum of the electric fields from all three slabs is aligned with the negative y-axis. 003 (part 1 of 2) 10.0 points A dipole (electrically neutral) is placed in an external field. + (a) + (b)- +- + + + + + + + + + + + + + +-------------------------- + + + + + + + + + + + + +- +- + (c) (d) For which situation(s) shown above would the net force on the dipole be equal to zero? 1. ( b ) only 2. ( a ) and ( b ) 3. ( c ) only 4. ( a ) only 5. ( a ) and ( d ) 6. ( b ) and ( d ) 7. ( c ) and ( d ) correct 8. ( d ) only 9. ( b ) and ( c ) 10. ( a ) and ( c ) Explanation: The force on a charge in the electric field is given by % F = q % E and the torque is defined as % T = %r × % F Δ % E = k Δ q r 2 ˆ r % E = Δ % E i ....
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This note was uploaded on 06/10/2011 for the course PHY 302l taught by Professor Morrison during the Summer '08 term at University of Texas at Austin.

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HW02-solutions - Munoz (gm7794) – HW02 – TSOI –...

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