1. The Final Round Kleenex available in departmental office

2. PHYS 115 EXAM Friday, Dec 14 10:30-11:20pm Brace 211 Brace 201 Ferg 112 One more time: While the final exam meets: PHYS 115 FINAL Friday, Dec 21 10:00-noon Brace 211 Brace 201 Brace 113N

3. Question 1 Your home water heater is rated at 4800 Watts for 120 volt electrical service. How much current does the heater draw? A. B. C.

4. Question 2 Your home water heater is rated at 4800 Watts for 120 volt electrical service. It draws 40-A of current. A. B. C. What is its total resistance? D.

5. This bar magnet is centered at the origin of a set of axes (+x points to the right, +y into the screen, and +z up toward the top of the page). P, Q, and R are points along each axis. x y z P R Q The magnetic field points ___ at position P. 1. left (-x) 2. right (+x) 3. in (+y) 4. out (-y) 5. up (+z) 6. down (-z) Question 3

6. This bar magnet is centered at the origin of a set of axes (+x points to the right, +y into the screen, and +z up toward the top of the page). P, Q, and R are points along each axis. x y z P R Q The magnetic field points ___ at position R. 1. left (-x) 2. right (+x) 3. in (+y) 4. out (-y) 5. up (+z) 6. down (-z) Question 4

7. This bar magnet is centered at the origin of a set of axes (+x points to the right, +y into the screen, and +z up toward the top of the page). P, Q, and R are points along each axis. x y z P R Q The magnetic field points ___ at position Q. 1. left (-x) 2. right (+x) 3. in (+y) 4. out (-y) 5. up (+z) 6. down (-z) Question 5

8. This solenoid is centered at the origin of a set of axes (+x points to the right, +y into the screen, and +z up toward the top of the page). P, Q, and R are points along each axis. x y I I z P R Q Question 6 The magnetic field points ___ at position R. 1. left (-x) 2. right (+x) 3. in (+y) 4. out (-y) 5. up (+z) 6. down (-z)

9. This solenoid is centered at the origin of a set of axes (+x points to the right, +y into the screen, and +z up toward the top of the page). P, Q, and R are points along each axis. x y I I z P R Q Question 7 The magnetic field points ___ at position P. 1. left (-x) 2. right (+x) 3. in (+y) 4. out (-y) 5. up (+z) 6. down (-z)

10. This solenoid is centered at the origin of a set of axes (+x points to the right, +y into the screen, and +z up toward the top of the page). P, Q, and R are points along each axis. x y I I z P R Q Question 8 The magnetic field points ___ at position Q. 1. left (-x) 2. right (+x) 3. in (+y) 4. out (-y) 5. up (+z) 6. down (-z)

11. Each figure below is a source of a magnetic field. For which, at its center, does that magnetic field point along the negative x direction (left)? + x xx Question 9

12. The south pole of a bar magnet approaches this conducting loop from behind. This induces A. a clockwise current in the loop. B. a counterclockwise current in the loop. C. no current in the loop. Question 10

13. A magnet dropped from high above, falls through a wire loop, its North-pole first. As the N-pole approaches the loop from above, the current generated in it, viewed from above will An induced current in the loop sets up a field of its own that exerts a force on the bar magnet. A. flow clockwise. B. flow counterclockwise. C. flow toward the magnet. D. flow away from the magnet. E. be zero. Question 11

14. A magnet dropped from high above, falls through a wire loop, its North-pole first. As the N-pole approaches the loop from above, the force between the bar magnet and the loop will be An induced current in the loop sets up a field of its own that exerts a force on the bar magnet. A. attractive. B. repulsive. C. zero. Question 12

15. A magnet dropped from high above, falls through a wire loop, its North-pole first. The moment the bar reaches halfway through the loop, the current at that instant will be A. flow clockwise. B. flow counterclockwise. C. flow toward the magnet. D. flow away from the magnet. E. be zero. Question 13

17. A magnet dropped from high above, falls through a wire loop, its North-pole first. The moment the bar reaches halfway through the loop, the current at that instant will be A. flow clockwise. B. flow counterclockwise. C. flow toward the magnet. D. flow away from the magnet. E. be zero. Question 13

18. A magnet dropped from high above, falls through a wire loop, its North-pole first. As the S-pole drops away from loop, the current generated within it, viewed from above will A. flow clockwise. B. flow counterclockwise. C. flow toward the magnet. D. flow away from the magnet. E. be zero. Question 14

19. + - When the switch is closed, the sudden influx of magnetic field induces a current in the metal ring which A. attracts the ring to the loop. B. repels the ring from the loop. C. neither attracts nor repels the ring. A coil is connected through an open switch to a battery. A thin metallic ring lies below the coil. Initially no current is drawn from the battery. Question 15

20. + - Once the switch is closed and steady current is established through the loop, the ring is A. attracted to the loop. B. repelled from the loop. C. neither attracted nor repeled. A coil is connected through an open switch to a battery. A thin metallic ring lies below the coil. Initially no current is drawn from the battery. Question 16

21. I The “Lorentz Force”

22. A conducting rod is drawn down through the B-field as shown. Free electrons in the rod will 1) flow through the hand to ground. 2) tend to bunch up at the far end. 3) be pushed to upper surface of the rod. 4) be unaffected. Question 17

23. Which one of the following items emits radio waves? (A) A stationary, vertical and uniformly charged metal flagpole. (B) A uniformly charged plastic stick spinning end-over-end in the air. (C) A stationary, horizontal uniformly charged metal flagpole. (D) A stationary loop of wire with a steady electric current flowing through it. Question 18

24. Charge vibrates linearly along the direction illustrated. This oscillation emits transverse waves preferentially in what direction? Waves are transmitted equally in all directions Question 19

25. E field points down E field points up E field momentarily zero strong weak zero E-field pointing down

26. The magnetron of a microwave horn generates a horizontally varying B-field and oscillating vertical E-field. We found which of the aluminum gratings below allows the microwaves To pass? 1 2 Question 20

27. Lecture 40: 20 Final Questions! Question: 1. CP = IV  I = P/V = 4800/120 = 40 Amp 2.BV = IR  R=V/I = 120/40 = 3  or P=V 2 /R  R=V 2 /P 3.6down, field lines point into the South pole 4.5up – the field lines double back, along the sides 5.5up – this side no different from above 6.2 the right-hand-rule should place your thumb at this end 7.1 like a bar magnet, field lines run back parallel with the magnet 8.1same as 5 above. 9. C a and b involve negatively charged electrons 10.B the S-pole introduces flux pointing into the page. To compensate the loop produces a counterclockwise current generating its own flux out of the page. 11.B To produce flux directed upward against the magnet’s. 12.BRepulsive. An N-pole faces up at the falling N-pole. 13. E There is no increase in flux through the loop as the middle of the magnet (where field lines are sparse and parallel with the magnet) moves past. 14.ANow flux is vanishing and must be replaced. 15. BThe opposing magnetic field induced, points an N-pole up. 16.C Steady current  no changing magnetic field  no induced current. 17.2 Positive charge collects near the hand, free electrons are pushed to the far end. 18.BThe twirling rod is the only moving charge. 19.4 Like transmitting antenna, the traveling E-fields are to the oscillating current. 20. 2 Receiving antenna, parallel with the E-field that drives current, will absorb the transited energy. A grid perpendicular to that will let the energy pass.