# Problems : Electric Charge and Electric Force

1. Two positive point charges, Q1 = 1 μC  and Q2 = 1 μC , are separated by a distance d. Which is larger in magnitude, the force that Q1 exerts on Q2 or the force that Q2 exerts on Q1  ?
2. What is the magnitude of the force a +25 μC charge exerts on a +2.5 mC charge 30 cm away?
3. How many electrons make up a charge of —38.0 μC ?
4. Particles of charge +75 μC, +40 μC, and —85 μC are placed in a line. The center one is 0.30 m from each of the others. Calculate the net force on each charge due to the other two.
5. Sophy scuffing her feet on a wool rug on a dry day accumulates a net charge of —46 μC.  How many excess electrons does she get, and by how much does her mass increase?
6.  A charge Q is transferred from an initially uncharged plastic ball to an identical ball 10 cm away. The force of attraction is then 18 mN. How many electrons were transferred from one ball to the other?
7.  Three charged particles are placed at the corners of an equilateral triangle of side 1.20 m. The charges are +7.0 μC —8.0 μC , —6.0 μC. Calculate the magnitude and direction of the net force on each charge due to other two.