1. Mon. Jan. 26 – Physics Lecture #22 The Electric Field 1. Forces & Fields 2. Superposition 3. Electric Field due to Continuous Charge Distributions

2. Example: An electron placed in a gravity field experience a gravity force of 6.1 x 10 –10 N. a) What is the magnitude of the gravity field? b) A proton is placed in that same gravity field. What is the magnitude of the gravity force on that proton? Example: An electron placed in an electric field experience an electric force of 6.1 x 10 –10 N. a) What is the magnitude of the electric field? b) A proton is placed in that same electric field. What is the magnitude of the electric force on that proton?

3. ConceptCheck: An electron moving to the right enters a region with electric field as shown. Which way does the electron deflect as it passes through the electric field? 1. Up 2. Down 3. Right 4. Left 5. Into or out of page 6. No deflection ?

4. PhET Interactive Simulations – Charges and Fields http://phet.colorado.edu/en/simulation/charges-and-fields

5. Example: The sketch shows two point charges located in the x-y plane: q 1 at the origin and q 2 at (0 m, 4 m). Also consider a field point at (3 m, 0 m) a) Determine the unit vector from q 1 to the field point. b) Determine the unit vector from q 2 to the field point. c) Determine the electric field at the field point due to q 1 and q 2. d) How does your answer change if q 2 is negative? e) A charge q 3 is placed at (3 m, 0 m). What is the electric force acting on q 3 ?