1. Unit 10: Electric Fields An electric force is a field force. Recall the difference between a field force and a contact force. ◦ Field forces act through space, producing an effect even when there is no physical contact between the objects involved.

2. Unit 10: Electric Fields Strength of an electric field and its effect on q 0 : E

3. Unit 10: Electric Fields Strength of an electric field (caused by Q) and its effect on q 0 :

4. Unit 10: Electric Fields Electric field is a vector quantity It has units of N / C We consider point charges like q 0 in cases like this because if q 0 is too large then it will cause redistribution of charges in Q

5. Unit 10: Electric Fields Electric field strength depends on charge and distance

6. Unit 10: Electric Fields

8. Electric field is a vector If q is positive, the field due to this charge is directed outward radially from q. If q is negative, the field is directed toward q.

9. Unit 10: Electric Fields Example: A charge q 1 = +7.00 μC is at the origin and a charge q 2 = -5.00 μC is on the x- axis 0.300 m from the origin. Find the electric field strength at point P, which is on the y-axis 0.400 m from the origin. (2.71x10 5 N/C at an angle of 66.6˚)

10. Unit 10: Electric Fields Electric field is a vector If q is positive, the field due to this charge is directed outward radially from q. If q is negative, the field is directed toward q.

11. Unit 10: Electric Fields A nice way to visualize electric field patterns is to use lines in the direction of the field.

12. Unit 10: Electric Fields The number of field lines is proportional to the electric field strength. The strength is strongest when the lines are closest together.

13. Unit 10: Electric Fields Examples: Sketch electric field diagrams for two charges of equal magnitude but one is positive and one is negative. Sketch electric field diagrams for two charges of equal magnitude but both are positive. Sketch electric field diagrams for two charges of where one charge is 3 times the magnitude of the other and both are negative.