University Physics - Electric Fields

Question 1 a) Two small plastic spheres each have a mass of 2.0 g and a charge of -50.0 nC. They are placed 2.0 cm apart (center to center). What is the magnitude of the electric force on each sphere? b) Two 1.5 g ball bearings are 2.0 cm apart. How many electrons must be transferred from one to the other so that, when released, they each initially accelerate toward the other with a = g? + 3.0 nC 5.0 cm Question 2 What are the strength and direction of the electric field at the position 10 cm indicated by the dot in the figure on the left? Specify the direction as an angle cw from the horizontal. Hint: Just like the net electric force due to multiple point charges, the net electric field due to multiple point charges is found using superposition (i.e., the vector addition of each individual -6.0 nC charge's electric field). Question 3 The electric field strength 10.0 cm from a very long charged wire is 2000 N/C. What is the electric field strength 5.0 cm from the wire? Hint: Refer to Chapter 23.3 for the electric field of an infinite line. Question 4 Two circular disks spaced 0.50 mm apart form a parallel-plate capacitor. Transferring 3.0 x 10" electrons from one disk to the other causes the electric field strength to be 2.0 x 10 N/C. What are the diameters of the disks? Hint: Refer to Chapter 23.5 for the electric field inside a parallel- plate capacitor. (optional) Challenge Problem Two positive point charges q and 4q are at x = 0 and x = L, respectively, and free to move. A third charge is placed so that the entire three-charge system is in static equilibrium. What are the magnitude, sign, and x-coordinate of the third charge