1. Lesson 3: Electric Fields
Electric field: the influence of a charge (or charges) on the surrounding space

2. Formal Definitions
Electric Field: The force that would be experienced by a +1 C point charge (Newton/Coulomb). E = F / Q
Electric Field Lines: Lines that show the direction and magnitude (density of lines) of the electric field.

3. Electric Field Example:
Draw the electric field lines surrounding a proton and find the magnitude of the electric field 1 cm away.
10 min

4. Try This: Draw the electric field lines…
5 min

5. Try This: Draw the electric field lines…
5 min

6. Brain Break!

7. Calculations of Electric Field Strength
“The force that would be “felt” by a +1 coulomb point charge.”
Example 1:
a) Find the electric field midway between two charges of 2.0 μC and 3.0 μC located 5.0 m apart.
b) Where is the electric field ZERO?
5 min

8. b) Where is the electric field ZERO?
a) Find the electric field midway between two charges of 2.0 μC and 3.0 μc located 5.0 m apart.
= 1440 N/C
b) Where is the electric field ZERO?
15 min
2.25 m left of the 2 μC charge

9. Homework Textbook pg. 149 #1-5 Problem Set – Part A #1, 2, and 7
10 min

10. Lesson 4: More Electric Fields

11. Example 2: What is the magnitude and direction of an electric field that just supports an electron`s weight?
10 min
Direction？
Downwards！

12. Practice Time! Find: a) The force on the -2 µC charge
The electric field at (3,0)
The electric field at (0,2)
Where the electric field is zero
The acceleration of an electron placed at (3,0)
30 min a)

13. b) c)
10 min
5400 N/C, 75O with the x axis

14. d) e)
From (b), the electric field is N/C.
10 min

15. Homework
Problem Set – Part A #3-6 (all of Part A has now been assigned)