# PHYS 206 002 Electricity and Magnetism

1. (20 points) In a thundercloud, there may be electric charges of +50.0 C near the top of the cloud and −100.0 C near the bottom of the cloud. These charges are separated by 2.00 km. What is the electric force on the top charge?

2. (20 points) Three point charges are arranged as shown below. Find (a) the magnitude and (b) direction of the electric force on the particle at the original.

3. (20 points) Three point charges lie along a straight line as shown below, where q1 = 10.00 µC, q2 = 2.00 µC, and q3 = −5.00 µC. The separation distance are d1 = 5.00 cm and d2 = 2.00 cm. Calculate the magnitude and direction of the net electric force on (a) q1 and (b) q2.

4. (20 points) Two small beads having positive charges q1 = 3q and q2 = q are ﬁxed at the opposite ends of a horizontal insulating rod of length d = 2 m. The bead with charge q1 is at the origin. As shown below, a third small, charged bead is free to slide on the rod. At what position x is the third bead in equilibrium?

5. (20 points) Two small metallic spheres, each of mass m = 0.100 g, are suspended as pendulums by light strings of length L as shown below. The spheres are given the same electric charge of 10.0 nC, and they come to equilibrium when each string is at an angle of θ = 5.00◦ with the vertical. How long is the strings?