A 4 nC charge is fixed at x = 0 m.  A 12 nC charge is fixed at x = 2.9 m.  (Note that 1 nC = 10-9 C)  Calculate the electric field at x = 1.9 due to these charges, in N/C.  Use k = 9 x 109 N m2 / C2.  Your answer could be positive or negative. (Please answer to the fourth decimal place - i.e 14.3225)

A charge of +3.17mC is placed in a region where an electric field is present.  If the magnitude of the electric field is 284.9 N/C, what is the magnitude of the electric force on this charge in units of Newtons? Note:  It is understood that the unit of your answer is in Newtons, however do not explicitly include units in your answer.  Enter only a number.

Find the electric field at P in the figure shown below. (Take r = 1.9 m and ? = 37°. Measure the angle counterclockwise from the positive x-axis.) magnitude   direction  °

A test charge of +3 µC is at a point P where an external electric field is directed to the right and has a magnitude of 4.0x106 N/C. The test charge is replaced with another test charge of -3 µC. The external electric field at P from the source chare will ________. (increase, decrease, remain the same.) How do you know this?