1: When a high voltage power line falls on your car, you are safe as long as you stay in the car; but if you step out, you may be electrocuted. Why? Is the inside of a car a safe place to be during a thunderstorm? Why or why not?

2: A spherical volume centered at the origin of coordinates with radius A, has a volume charge density r (r)=+Q(B/r²), where B is a constant with units of m^-1. Calculate the electric field for r<a and for r>a.

3: When a thunderstorm is approaching , sailors at sea sometimes observe a phenomenon called "St. Elmo’s fire," A bluish flickering light at the tips of masts. What causes this?

4: Draw the electric field "lines of force" and the equipotential lines in a plane containing two + charges separated by a distance d. Now consider two infinite, positively charged power lines parallel to each other. Draw the electric field lines and the equipotential lines in a plane perpindicular to the power lines.

5: If the electric field is zero in a region of space, which of the following is always true:

1. the potential is zero
2. the potential is constant
3. the potential is negative
4. the potential depends on the size of the region of space

6: A charge of 37 nC is placed in a uniform electric field that is directed vertically upward and that has a magnitude of 5x10⁴ N/C. What work is done by the electric force when the charge moves (a) 0.450 m to the right; (b) 0.670 m downward; (c) 2.60 m at an angle of 45 degrees upward from the horizontal?

7: A small sphere with a mass of 3.20 g hangs by a thread between two parallel vertical plates 5.00 cm apart. The charge on the sphere is q= 5.8x10-6 C. What potential difference between the plates will cause the thread to assume an angle of 30.0 degrees with the vertical. This is problem 24-54 in the text. You can see a diagram on page 766.