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# I need some help/explanation to better understand these practice questions.. Thank You............................

1 Suppose that you have constructed an MRI machine with a 1.9 m-long solenoid that has 16, 000 coil turns and results in a 0.5 T magnetic field on its interior. If you were to plug this machine into a power supply that runs the machine at 300 V, what would be the ratio of the power consumption of this machine to the power consumption of a 40 W light bulb?............................... 2 Protons in space near the Earth orbit the Earth's magnetic field in a region where the magnetic field is nearly constant. The protons have circular orbits, and they execute about one thousand orbits every second. What is the strength (magnitude) of the magnetic field in this region? ......................................3. Suppose that a stream of protons is moving along a straight path perpendicular to this page, and the stream is moving into the page. We take the page to be in the xy-plane, and we suppose that the path along which the protons are moving intersects the page at the point (1 cm, 0 cm). An electron is at point (x,y) = (3 cm, 1 cm) and has velocity (vx, vy) = (−5 × 104 m/s, 0 m/s). Will the electron's path curve into the page, out of the page, or will it just keep moving straight with its current velocity? Write either "into," "out," or "straight" in the answer box, and explain your reasoning............................ 4. Suppose that there is a constant magnetic field in the xy-plane with magnitude 10−5 T, and an electron is moving with a speed of 2.8 × 104 m/s at a 30◦ angle relative to the field. What is the magnitude of the acceleration of the electron assuming it only experiences the force due to the magnetic field? .................................5. Consider figure P24.30. What magnetic field strength and direction will levitate the wire if it has a mass of 3 g, current of magnitude 5 A to the left, and if the B-field region overlaps with the length of the wire for 12 cm?.......................... 6. A long, straight wire carrying a 5 A current perpendicular to the xy-plane intersects the x-axis at x = 2 cm. Another straight wire carrying a 3 A current perpendicular to the xy-plane intersects the x-axis at x = 4 cm. At what point(s) along the x-axis is the magnetic field zero if the two currents are in the opposite direction? If there are no such points, write "None" and show your reasoning. ...................................... 7. A current loop in a motor has an area of 0.76 cm2 and carries a 240 mA current in a uniform field of 0.62 T. What is the magnitude of the maximum torque on the current loop? .......................................8. A square current loop 4.1 cm on each side carries a 710 mA current. The loop is in a 0.87 T uniform magnetic field. The axis of the loop, perpendicular to the plane of the loop, makes an angle 30◦ relative to the magnetic field direction. What is the magnitude of the torque on the current loop? ....................................... 9. A certain transmission line has a wire that is around 12 m o the ground. How much current would have to be running through the line so that the magnetic field on the ground right under the line has about the same magnitude as the magnetic field of a refrigerator magnet? Note: table 24.1 in the book lists the magnetic field strength in some real scenarios....................Thank you

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