1. How does a ____________ (or a collection of ____________) exert a force on another _____________ from a distance ? charged object A charged object B Answer: By means of their electric ________________. (Note: The letter E can also represent ______________.) III. ____________ Fields

2. An electric field E exists around ___________________. Its strength is found by placing a positive "__________________" (any charge) q in the field and measuring the electric force F e that ________________. E = E is a _______________ because it has ______________. Its direction is given by the direction of the _____________ ____________ that acts on the __________________________ that is placed in the field units of E: E = F e / q [ E ] = [ ]/[ ] = / where q is the _______ charge

3. Ex 1: A positive charge q = 5.0 mC experiences an electrical force of 10.0 x 10 3 N when placed at the position shown. Determine the strength and direction of the electric field at the point shown. strength : E = = q direction : (__________ direction as ____)

4. Ex 2: What electrical force will a proton experience when placed in the electric field at point P shown below? magnitude : = = Ex 3: What electrical force will an electron experience when placed in the same point as the previous example? P E = ____________ direction : ______________ direction as _____ magnitude: _________________ direction: __________________

5. Ex 4: The E field around a ______________ point charge q p + qpqp

6. Note: 1.The arrows represent “_________________” that act on a ______________ test charge q. 2.E is directed _____________________ away from “____” 3. The closeness of the lines show the field ___________. The arrows show ________________ because they point ______________________. 5. Field lines _________________, because if that were true, the field would have ______________________________ 6. E is _________________________. It is NOT constant.

7. For a point charge: Let q 1 = the __________ charge q p, and q 2 = the __________ charge q, Then, _________________ Law: F e = kq 1 q 2 /r 2 becomes F e = and E = F e /q becomes E = EE qpqp r For a point charge:

8. Ex 5: The E field around a ____________ point charge. Note: 1.The arrows represent “__________________________.” 2. E is directed radially __________ towards the ___. 3. E is __________________________. It is NOT constant. 4.The _________________ of the lines represents the field strength. 5.The arrows show ________________because they point __________________. 6.This E resembles Earth’s _____________________ field as it would be seen _____________________ -

9. Ex 6: The E field around 2 __________________ charges. Start by placing a ____ test charge q at one point. Find resultant of the forces from both charges on q. + - Then repeat for every other possible point. where F e+ = F e due to the ___charge and F e- = Fe due to the ___charge The result will be… q

10. Note: 1. Near each charge, E is like that of a ___________ charge. 2.The direction of the force at any point is ______________ to the field lines. 3.Lines are always: ____ ________ the “+ and ___________ the “-” 4.E lines ______________ cross b/c the net force at any point ____________________________________.

11. Ex. 8: The E look like around two ______________ charges will look _______________________ but with ______________________________________ Ex. 7: For two _________________ charges, E will look like:

12. Ex. 8: The electric field around two charged ___________________________ Notes: 1. Lines are ____________ “+" and _________________ “-” 2. Within the plates, E is _______________. _______________ spaced lines  ____________ field 3. Same idea as the constant ___________________ field near Earth’s ________________. 4. In reality, the lines near the edges ___________________ positive negative

13. Suppose ___________________ is placed between the plates and released from rest. The strength of the electric field is __________________. What direction will the electrostatic force on it be? After released, it will fall _____________. Its acceleration will ____________________ because the _________________ __________________________ in the ______________ E field. Compare the electrostatic force to the gravitational force. F g = w = mg = F e = qE =

14. In region A, it follows a ____________________ because the net force acting on it is _________________. Within the plates, it follows a ____________________ because the net force acting on it is _________________ In region B, it follows a ____________________ because the net force acting on it is _________________. Suppose an e - is fired ___________________ between the plates. Draw its trajectory. Ignore gravity. vivi A B initial direction

15. Ex. 9: Two interesting facts: 1.Any charge placed on a conductor ____________________ ___________________________. 2. The E field inside any conductor is ____________. This is called ______________________________.

16. You are a __________________. E field lines "end on" the surface of a conductor and___________________. Painting rooms with a _______________ paint prevents ( electro magnetic) radio signals from entering.