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ANSWERS QUIZ 20

Problems 4, 6, 12, 14, 16, 28, 40, 42, 44, 46

4. 2.3x10 ^-4 (N)

6. 20 degrees

12. ( a) downward (b) into the paper (c) right

14. 1.6 m

16. While electric field is on: v = 2.5x10 ⁶ m/s . After the electric field is turned off: r = 4.1 x10 ^-3 m.

28. In all cases your right thumb points out in the direction of the current and your right fingers curve counter clockwise. See Table 20-1, point 1., the magnetic field due to a long wire.

40. I = 19.4 (A) into the page for the diagrams I drew on the board for this problem. In the those diagrams the magnetic field from the wire was vertically down, which is the correct direction from the right hand rule , Table 20-1 , point 1.

42. (a) 6700 (A) , right. (b) unstable (c) 6700 (A), left.

44. Assume the two parallel currents flow out of the page. You can have the wires horizontally displaced from one another. Let wire B be positioned to the right of wire A, i.e. wire A is on the left and wire B is on the right. When you hand in this problem, please show a diagram reflecting this set up. Assume the currents are out.

(a) 2.7x10^-6T, up (b) 5.3x10 ^-6 T, down. (c) not equal and opposite (d) 1.1x10 ^{- 5} N/m.

46. magnitude B_net = 1.75x10 ^-4T. The net field points 14 degrees below the positive x-axis, in the fourth quadrant.