1. A hydrogen atom is composed of a nucleus containing a single proton, about which a single electron orbits. The electrical force between the two particles is 2.3  10 39 greater than the gravitational force! If we adjust the distance separating the two particles, can we find a separation at which the electrical and gravitational forces are equal? 1) Yes, by moving the particles farther apart. 2) Yes, by moving the particles closer together. 3) No, at any distance.

2. 3 meters +16  C+4  C Where is the net electric field between these two charges ZERO? d3 meters - d 0 Ans. d = 1 meter

3. 4 discrete charges of magnitude, q, and the indicated signs, occupy the corners of a rectangle as shown. The direction of the electric field, E, at the point shown is: 1) up 2) left 3) right 4) down 5) other +q qq qq 1 23 4

4. 4 discrete charges of magnitude, q, and the indicated signs, occupy the corners of a rectangle as shown. The direction of the electric field, E, at the point shown is: 1) up 2) left 3) right 4) down 5) other +q qq qq 1 23 4

5. 4 discrete charges of magnitude, q, and the indicated signs, occupy the corners of a rectangle as shown. The direction of the electric field, E, at the point shown is: 1) up 2) left 3) right 4) down 5) other +q qq qq 1 23 4

6. 3) No, at any distance. QUESTION 1 Gravity and the electrostatic force between proton and electron both vary as 1/R 2 ! This means they both increase in proportion as they are brought closer together. 5) other QUESTION 2 At the very center the electric field due to any single charge is exactly opposite to the field created by the charge at the opposite corner! 1) up QUESTION 3 + + - - Net electric field is up. 2) left QUESTION 4 + + - - Net electric field is left.

7.  +

8. +2 q -3q-3q