1. Describe how a negatively charged balloon would interact with: -another negatively charged balloon -your positively charged hand -two positively charged hands on either side, equal distance apart Broadneck High School

2. Outcome: The student will be able to identify and calculate properties of electric fields through written practice and student led instruction. Broadneck High School

3. What will we actually be doing?  Drill  Outcome  Review  Quiz  Power point  Classwork Broadneck High School

4. Electric Fields Broadneck High School Chapter 21.1: Creating and Measuring Electric Fields

5. Remember the Balloon Lab?  How did the balloons react?  Did it work in three dimensions?  What else creates forces in 3 dimensions? Broadneck High School

6. Relationship to gravity  Much like gravity, electric force is inversely proportional to the distance squared  Fg = GM 1 M 2 /d 2  F = Kq 1 q 2 /d 2 Broadneck High School

7. How can a force be exerted across what seems to be empty space?  Michael Faraday suggested that because an electrically charged object, A, creates a force on another charged object, B, anywhere in space, object A must somehow change the properties of space. Object B somehow senses the change in space and experiences a force due to the properties of the space at its location. We call the changed property of space an electric field. Broadneck High School WHAT???

8. In simple terms:  An electric field means that the interaction is not between two distant objects, but between an object and the field at its location. Broadneck High School

9. Electric Fields  Can do work, transferring energy  This is shown when using appliances Broadneck High School

10. How do we calculate electric fields? Broadneck High School  Place a small charged object at some location.  If there is an electric force on it, then there is an electric field at that point.  q’ is the symbol for test charge

11. F is in Newtons q is in Coulombs What is E going to be in? Broadneck High School

12. Test Charge  Smaller test charge (q’) = what force?  Larger test charge magnitude = what force?  Does electric field magnitude change with different test charge size?  What happens if you use too large a test charge? Broadneck High School

13.  All are vector quantities  For charge use + or -  Mr. Schwenke and Mr. Witmer recommend using words for direction not + or - Broadneck High School

17. Drawing electric Fields  Positive charges push things away  Negative charges pull things towards  Field lines should be in proportion to charge Broadneck High School

18. Creating electric fields  http://www.cco.caltech.edu/~phys1/java/ phys1/EField/EField.html Broadneck High School

19. Exit ticket  Take out a piece of paper and draw an electric field between a +1 charge and a -2 charge Broadneck High School