B C 土井 Figure 1 Figure 2 N y H Figure 3 Z Figure 4 1. Figure 1 shows a representation of a long, straight wire carrying a current in the direction indicated. The wire and points A, B, and C are all in the same plane. At which point(s) in the figure will there be a magnetic field that is directed into the page? 2. If the field at point A in Figure 1 has a magnitude of 60 μT, the field at point C will be... a) 15 μT b) 30 μT c) 60 μT d) 120 μT e) 240 μT 3. If the field at point B in Figure 1 has a magnitude of 60 μT when the current in the wire is 4.5 A, what is r? 4. Figure 2 shows a path around two wires with currents in opposite directions. How would you calculate the value of f B. di for that path? α) μο 11 12 b) μο (11 - 12) c) Ho (I1 + I2) d) μο (12 - Ι1) 5. In Figure 3, the central dot represents a straight wire that is perpendicular to this page. The other parts of the diagram show compass needles. What direction is the current in the wire? b) Out of the page c) There is no current. a) Into the page 6. Figure 4 shows a representation of a conducting loop carrying a clockwise current in a region where there is a uniform magnetic field directed to the left. If the conducting loop is free to move, it will tend to rotate. Which axis is parallel to the axis of rotation of the loop? 7. If the length of one side of the square loop in Figure 4 is 20 cm, what is the magnetic flux through the loop due to an external field of strength B = 45 mT? 8. Recalculate your answer to Question 7 for the situation after the loop has reached its equilib- rium position (after rotating as predicted in Question 6). 9. The lights on the nose and tail of a plane are 20 m apart and are synchronized to flash at the same time (according to observers in the plane). As this plane flies over at a speed of 0.40c, observers on the ground make detailed measurements of the time and position that the lights flash. According to Special Relativity, if both sets of observers treat a flash of the light at the nose of the plane as the origin of space and time, the observers on the plane will record the simultaneous flash of the light at the tail of the plane as having coordinates (t = 0, x = -20 m). But the observers on the ground will measure that event as taking place at (t = -8.73 m, x = -21.8 m). What is the time delay, in seconds, between the flashes of the two lights (the nose and the tail) according to the observers on the ground, and which light do they see flash first? 10. In Figure 5, an electron is shot with velocity into the gap between two charged plates. It is possible to have the electron pass straight through the gap if a strong, external magnetic field is applied to the region between the plates. What direction should that magnetic field be? +++++++++ a) b) Figure 5 TIT E X X X X X X c) d) e) X X X f) 000 12. 11. In Figure 6, a charged particle is moving in the direction shown. If the magnetic force on the particle at that instant is directed out of the page, which of the following could be the direction of the magnetic field in the region around the charge? (a) (b) (c) (d) X X X X X X (e) X X X (f) O O O OOO O O O + Figure 6 At some point in time, an ionized carbon dioxide molecule has a velocity of = 25 km/s. The ionization stripped off an electron. Thus the charge of the molecule is the same as a proton, but the mass is 7.3 x 10-26 kg. For the following questions, assume that the molecule is always inside a region of uniform magnetic field B = -0.050 T 2. (a) What is the size of the magnetic force that acts on the particle? (b) Sketch a diagram of the motion of the particle. Indicate the direction of the magnetic field, the direction of the particle's motion, and the direction of the force on the particle in at least two different positions. (c) The motion of the particle should be periodic. Calculate how long it takes for it to return to a particular position in its path.