Problem 1:

A thin glass rod of length 8.0cm that is uniformly charged to +8.0 nC and an equally long thin plastic rod uniformly charged to -8.0 nC are placed side by side, 4.0 cm apart (see figure). What are the electric field strengths E1 to E3 at distances 1.0 cm, 2.0 cm, and 3.0 cm from the glass rod along the line connecting the midpoints of the two rods?

Problem 2:

In an inkjet printer, letters and images are created by squirting drops of ink horizontally at a sheet of paper from a rapidly moving nozzle. The pattern on the paper is controlled by an electrostatic valve that determines at each nozzle position whether ink is squirted onto the paper or not.

Referring to the figure at right: The ink drops have a mass m each and leave the nozzle and travel horizontally toward the paper at velocity vx The drops pass through a charging unit that gives each drop a positive charge q by causing it to lose some electrons. The drops then pass between parallel deflecting plates of length D0, where there is a uniform vertical electric field with magnitude E.

If a drop is to be deflected a distance d by the time it reaches the end of the deflection plate, what magnitude of charge q must be given to the drop? Express q as simply as possible in terms of the symbols provided.