Here are this weeks questions. I don't need them until Sunday, but just sumbit something by Friday before we lose the time for this week. It says it refreshes at 1:59 am on March 1. But then you can submit the rest by Sunday evening. And Spring Break starts the 7th, so you have a free week coming to you, and I will just give the time to you.
2. The magnetic field B in a certain region is 0.128 T, and its direction is that of the +z axis in Figure21.47 (below). a) What is the magnetic flux across the surface abcd in the figure? b) What is the magnetic flux across the surface befc? c) What is the magnetic flux across aefd? d) What is the net flux through all five surfaces that enclose the shaded volume?
6. In a physics laboratory experiment, a coil with 200 turns enclosing an area of 12 cm^2 is rotated from a position where its plane is perpendicular to the earth's magnetic field to one where its plane is parallel to the field. The rotation takes 0.040 s. The earth's magnetic field at the location of the laboratory is 6.0 x 10^-5 T. a) What is the total magnetic flux through the coil before it is rotated? After it is rotated? b) What is the average emf induced in the coil?
9. A 30 cm x 60 cm rectangular circuit containing a 15 ohm resistor is perpendicular to a uniform magnetic field that starts out at 2.65 T and steadily decreases at 0.25 T/s. See figure 21.48 below. While this field is changing what does the ammeter read?
14. Using Lenz's law, determine the direction of the current in resistor ab of figure 21.52 when a) switch S is opended after having been closed for several minutes; b)coil B is brought closer to coil Awith the switch closed c)the resistance of R is decreased whiel the switch remains closed.
22. When a thin 12.0 cm iron rod moves with a constanct velocity of 4.50 m/s perpendicular to the rod in the direction shown in Figure 21.59, the induced emf across its ends is measured to be 0.450 V. a) What is the magnitude of the magnetic field? b) Which point is at a higher potential, a or b? c)If the bar is rotated clockwise by 90 degrees in the plane of the paper, but keeps the same velocity, what is the potential difference induced across its ends?
27. A toroidal solenoid has a mean radius of 10.0 cm and a cross-sectional area of 4.00 cm^2and is wound uniformly with 100 turns. A second could with 500 turns is wound uniformly on top of the first. What is the mutual inductance of these coils?
29. Two coils are wound around the same cylindrical form. When the current in the first coil is decreasing at a rate of 0.242 A/s. the induced emf in the second coil has magnitude 1.65 mV. a) What is the mutual inductance of the pair of coils? b) If the second coil has 25 turns, what is the average magnetic flux through each turn when the current in the first coil equals 1.20 A? c) If the current in the second coil increases at a rate of 0.360 A/s, what is the magnitude of the induced emf in the first coil?
32. A 4.5 mH toroidal inductor has 125 identical equally spaced coils. a) if it carries an 11.5 A current, how much magnetic flux passes through each of its coils? b) If the potential diffence across it's ends is 1.16 V, at what reate is the current in it changing?
33. At the instant when the current in an inductor is increasing at a rate of 0.0640 A/s, the magnitude of the self-induced emf is 0.0160 V. What is the unductance of the inductor?
39. You plan to take your hair blower to Europe, where the electrical outlets put out 240V instead of 120V seen in the US. The blower puts out 1600 W at 120 V. a) What could you do to operate your blower via the 240V line in Europe? c) What resistance will your blower appear to have when operated at 240V?