1. Warm Up Grade the HW Grade the HW 105 Pts 105 Pts

2. AP Physics Lesson 48 Magnetic Fields

3. Electricity and Magnetism A match made in heaven????? A match made in heaven?????

4. Parts of a magnet North vs. South North vs. South Not the Civil War Not the Civil War North is attracted to South North is attracted to South The north end of a magnet aligns with the North Pole The north end of a magnet aligns with the North Pole

6. Magnets Magnetic Domains Magnetic Domains Aligned creates a magnet Aligned creates a magnet Electron spin Electron spin How to make a magnet How to make a magnet How to make a magnet go bad How to make a magnet go bad

7. Magnetic Fields Force fields around magnets Force fields around magnets Created by moving electric fields generated by a moving charge Created by moving electric fields generated by a moving charge Symbol for magnetic field is B Symbol for magnetic field is B Measured in units of Tesla (T) Measured in units of Tesla (T)

8. Drawing Magnetic Fields

11. Use multiple lines to show uniform magnetic fields Use multiple lines to show uniform magnetic fields 3D 3D Into the page (x) Into the page (x) Out of the page (.) Out of the page (.)

12. Magnetic Force Magnetic fields create forces on moving charges Magnetic fields create forces on moving charges Causes a change in direction Causes a change in direction Proportional to the size of charge Proportional to the size of charge Proportional to the speed of the charge Proportional to the speed of the charge Proportional to the size of the field Proportional to the size of the field F B F B

13. Magnetic Force F B = qvBsinθ F B = qvBsinθ A charge moving at an angle to the field experiences less of a force A charge moving at an angle to the field experiences less of a force Helical Motion Helical Motion

15. Right Hand Rule Helps us predict the direction of the force Helps us predict the direction of the force Predicts which way the charge will be deflected Predicts which way the charge will be deflected

16. RHR

17. Example I A proton moving from left to right with a velocity of 305m/s enters a magnetic field that is perpendicular to the plane of the paper (coming out of the page). The strength of the field is 44T. Find the magnitude and direction of the force on the proton as it enters the field. A proton moving from left to right with a velocity of 305m/s enters a magnetic field that is perpendicular to the plane of the paper (coming out of the page). The strength of the field is 44T. Find the magnitude and direction of the force on the proton as it enters the field.

18. Answer 2.1x10 -15 N down. 2.1x10 -15 N down.

19. Example II An electron travels at 2.0x10 7 m/s to the right at it enters a 0.010T magnetic field directed into the page. A) Determine the magnitude of the force acting on the charge. B) Determine the direction of the force. C) Sketch the magnetic field and path the charge takes. Describe the path as moving either clockwise or counterclockwise. An electron travels at 2.0x10 7 m/s to the right at it enters a 0.010T magnetic field directed into the page. A) Determine the magnitude of the force acting on the charge. B) Determine the direction of the force. C) Sketch the magnetic field and path the charge takes. Describe the path as moving either clockwise or counterclockwise.

20. Answer 3.2x10 -14 N down and clockwise. 3.2x10 -14 N down and clockwise.

21. Example III A charge of 8.1x10 -9 C enters a magnetic field with a speed of 2200m/s at an angle of -30°. The 4.0T magnetic field is moving from left to right. Determine the magnitude of the force the field exerts on the charge. A charge of 8.1x10 -9 C enters a magnetic field with a speed of 2200m/s at an angle of -30°. The 4.0T magnetic field is moving from left to right. Determine the magnitude of the force the field exerts on the charge.

22. Answer 3.6x10 -5 N. 3.6x10 -5 N.