2. W10D2

3. Important Dates November 11th, 2010 Veterans Day November 25th, 2010 Thanksgiving Holiday December 6th, 2010 Last day of classes December 7th, 2010 Final exams begin December 11, 2010 Probable date for 2054 Studio Final (7:30AM ?) December 16th, 2010 Grades due on myUCF

4.  We continue with magnetism with a study of induction.  Next will be inductors.  Following inductors will be the next examination.  Quiz on Friday  Problem Session next Monday

5. I I A What is the direction of the magnetic field due to these two currents at point A? ALeft BRight CIn DOut E Other direction Clique

6.  There are “natural” magnets (like a compass) that have a magnetic field associated with them.  Electric Currents produce magnetic fields.  Like the field around a wire.  Moving charges in a magnetic field experience forces.  Electric Currents in magnetic fields also experience forces (BiL).  NEXT: CHANGING MAGNETIC FIELDS produce currents in loops of wire. This is called induction and this will be started today.

7.  Chapter 21  Sections 1-7  Chapter 22  Sections 1-5  Sections 8-9 You should have been reading Chapter 21 and should begin 22 now

8. A beam of protons moves in a circle of radius 0.25 m. The protons move perpendicular to a 0.20-T magnetic field. (a) What is the speed of each proton? (b) Determine the magnitude of the centripetal force that acts on each proton. 4.79e+06m/s 1.53e-13N

9. A particle is going around in a circle in a magnetic field that is perpendicular to the plane of the circle with a radius r and a velocity v. If the magnetic field is increased, the radius will: A increase Bdecrease Cremain the same Dexplode

10. When beryllium-7 ions (m = 1.165 10 -26 kg) pass through a mass spectrometer, a uniform magnetic field of 0.2503 T curves their path directly to the center of the detector (see figure below). For the same accelerating potential difference, what magnetic field should be used to send beryllium-10 ions (m = 1.663 10 -26 kg) to the same location in the detector? Both types of ions are singly ionized (q = +e)

11. A proton with a speed of 3.63 10 6 m/s is shot into a region between two plates that are separated by a distance of 0.24 m. As the drawing shows, a magnetic field exists between the plates, and it is perpendicular to the velocity of the proton. What must be the magnitude of the magnetic field so the proton just misses colliding with the opposite plate? 0.158 T

12. Two coils have the same number of circular turns and carry the same current. Each rotates in a magnetic field as in the figure below. Coil 1 has a radius of 5.2 cm and rotates in a 0.13-T field. Coil 2 rotates in a 0.42-T field. Each coil experiences the same maximum torque. What is the radius (in cm) of coil 2?

13. Suppose in the figure that I 1 = I 2 = 21 A and that the separation between the wires is 0.016 m. By applying an external magnetic field (created by a source other than the wires) it is possible to cancel the mutual repulsion of the wires. This external field must point along the vertical direction. What is the magnitude of the external field? D