1. A plastic pipeis rubbed with silkuntil it develops a charge of -9.7 coulombs. How many extra electrons did the silktransfer to the pipe?
2. Evaluate the force between point charges 3.4 mC and 7.3 mC separated by 4.9 cm in air.
3. A line of three-point charges is established. A charge of 8 micro coulombs is to the left of a charge of 5.9 micro coulombs, which is to the left of a charge of -7.7 micro coulombs. Each consecutive charge pair is separated by 2.2 cm. Calculate the magnitude and direction of the force acting on the middle charge. After the units, including the direction (left or right).
4. An electricdipole is made up of two identical and opposite charges that are separated by a fixed distance. The magnitude of the charges in such a dipole is 7.3 uC, and the separation of the charges is 1.7 mm. Determine the electric field strength at a distance of 8.7mm along on the perpendicular line that straddles the charges.
5. The following microcoulomb charges are found at the corners of an 8.9 cm square: 6.4, -12.8, 6.4, and -32. Determine the magnitude of the force acting on the -12.8 charge.
6. A rectangle with dimensions of 2.8 cm in length and 2.5 cm in width has its left width on the positive y-axis and its lower length on the positive x-axis. The origin has a point charge of -2.3 uC, and the other three corners have point charges of 2.3 uC. Determine the magnitude of the x-component of the force at the origin.

7.A distance of 2.4 cm separates two point charges of 9.6 uC and -9.5 uC. Determine the magnitude of the electric field strength in the middle of the charges.