1. 17.2 and 17.3 Electric Forces and Fields pp. 635 - 552 Mr. Richter

2. Agenda  Warm Up  Review HW  Discuss Upcoming Schedule  Notes:  Electric Force  Electric Fields  Electric Field Lines

3. Objectives: We Will Be Able To…  Calculate electric force using Coulomb’s law.  Calculate electric field strength.  Draw and interpret electric field lines.

4. Warm-Up:  What is a field force? Use your book if necessary (try the index!).

5. Electric Force

6.  Electric charges are attracted to and repelled by each other.  This pull or push is an electric force exerted on each charge.  The magnitude of the electric force depends on:  the size of the charges (how many extra electrons or protons)  the distance between the charges

7. Electric Force: Coulomb’s Law  The magnitude of the force between two charges can be calculated using Coulomb’s Law.  k C is the Coulomb constant:

8. Electric Force: Your Turn  The electron and proton of a hydrogen atom are separated, on average, by a distance of about 5.3 x 10 -11 m. What is the magnitude of the electric force each particle exerts on the other?  Find the magnitude of the charges on p. 630.  F electric = 8.2 x 10 -8 N

9. Electric Fields

10.  Electric forces are field forces. Meaning that:  No physical contact is necessary.  Acts in all direction at once.  All charged objects create electric fields that surround them.  An electric field is the region in space where any charged object feels an electric force.

11. Electric Fields  The electric field strength (E) is a ratio of force to charge.  How many Newtons of force does each Coulomb of charge experience? only for relatively large fields  Units of electric field strength are [N/C]

12. Electric Field Lines

13.  To visualize the electric field, electric field lines are drawn.  Rules:  Lines are drawn from positive charge to negative.  Number of lines drawn in proportional to strength of charge.  Lines do not cross.

14. Electric Field Lines  Electric field lines show the combinations of electric fields from more than one charge.  Opposite, equal charges.

15. Electric Field Lines  Electric field lines show the combinations of electric fields from more than one charge.  Like, equal charges.

16. Electric Field Lines  Electric field lines show the combinations of electric fields from more than one charge.  Opposite, unequal charges.

17. Wrap-Up: Did we meet our objectives?  Calculate electric force using Coulomb’s law.  Calculate electric field strength.  Draw and interpret electric field lines.

18. Homework  p. 636 #3, 4  p. 656 #41, 42  p. 657 #55