4. When a glass rod is rubbed with a silk cloth, the rod acquires a charge of magnitude 3.45 nC.

a. Did the glass rod gain or lose electrons?

b. How many electrons were transferred during the process?

c. What is the change in the mass of the glass rod? (Hint: Identify the total mass of electrons removed during the charging process)

d. What is the change in the mass

5. In the process of rubbing the lenses of the eyeglasses, 6.28 x 1010 electrons were transferred.

a. What is the charge of the lenses and the nylon cloth?

b. What is the change in their masses?

Electric Charges, on the section conservation of charges.

6. Metal sphere A has a net charge of +6.0 C, It is brought in contact with a neutral metal sphere B and then separated. Find the final charges on spheres A and B if

a. the spheres have equal radius and

b. if the radius of sphere B is twice the radius of sphere A

7. Spheres A, B, and C have charges +8.0 C, +12.0 C, and -5.0 C, respectively. The three spheres are allowed to touch each other simultaneously and then separated

a. What is the total charge on the three spheres before and after touching each other?

b. What is the final charge on each sphere assuming they are identical?

c. What is the final charge on each sphere assuming that A= 2rc (HINT: Assume that the charge acquired is directly proportional to radius )

8 Sphere A has an initial charge qo. How many successive contacts with an uncharged identical sphere A to 1/32

of its initial charge?

9. Spheres A, B, and C have charges +8.0 C, +120 C, and -5.0 C, respectively. Spheres A and B touched each other and then separated. Sphere A then touched sphere C and then separated.

a. What is the total charge on the three spheres before and after touching each other?

b. What is the final charge on each sphere assuming they are identical?

c. What is the final charge on each sphere assuming that ra=rb=2rc? (r refers to radius)

Coulomb's Law

1. Two protons are separated by a distance of 3.8x10-10 m in air. (a) Find the magnitude of the electric force one proton exerts on the other. Is this force attractive or repulsive? (b) Find the magnitude of the gravitational force one proton exerts on the other. Is this force attractive or repulsive?

2. Two small conducting and identical spheres A and B have charges - 25 nC and +15 nC, respectively. They are separated by a distance of 0.02 m. (a) What is the magnitude of the electric force between the two spheres? Is this force attractive or repulsive? (b) The spheres are then allowed to touch each other and then separated. What is the magnitude of the force between the two spheres? Is this a repulsive force or an attractive force?

3. Two particles A and B are released from rest, having equal charges of-5 x 10-6 C and initially separated from each other by 0.025 m. The masses of particles A and B are 5.25 x 10-6kg and 3.75 x 10-6 kg, respectively. Find the magnitude of the initial accelerations of particles A and B.

(HINT: After finding the electric force, apply the Newton's Second Law of Motion)

4. Two identical metallic spheres are suspended as bobs of a simple pendulum as shown in the figure. The spheres come to equilibrium when given a charge of +7.5 x10-9C each, with each string making an angle 5 with the vertical. The string is 0.5 m long. Find the electric force between the spheres

50150 0.5 m 0.5 m X 5. Determine the ratio of the electric force to the gravitational force between an electron and a proton when separated by a distance r. 6. Spheres A and B have the same initial positive charge q0. The magnitude of the repulsive electric force between the two spheres is 14.4 N when separated by a distance of 0.03 m. (a) Find the initial charge q0. (b) The spheres are then allowed to touch each other and then separated. Find the electric force between them if the radius of sphere A is three times that of sphere B. 7. A proton and an electron are initially at rest at a distance of 9x10 m. What will be their initial acceleration due to the electric force that they exert on each other? 8. A small sphere of charge +6x10 C is suspended from a string of negligible mass. A charge of -9.0x10C is placed directly to the right of the sphere and 0.22 m away11. Four point charges (two with q=2.50X10 C and two with q=-2.50x10 C) are situated at the corners of a square of side 1.00 m as shown. Find the resultant force that the charge at A will experience due to the charges at the other comers of the square. +q A C D