1. Calculate the number of electrons that must be removed from an uncharged object to give it a positive charge of 3.8 x 10-14 C. 2. Calculate the magnitude of the electric field and the electric potential at a distance of 0.35 m from an object with an excess of 6.1 X 10* electrons. TH6. Sphere A has a mass of 4.2 x 10 2 kg and is tethered to a wall by a thin thread. Sphere A has an excess of 1.2 x 10" electrons. Sphere B has a deficit of 3.5 x 10" electrons and is 0.23 m from sphere A (Figure 4). T thread B 0.23 m Figure 4 (a) Determine the angle between the thread and the wall. (b) Determine the tension in the thread. 7. Earth has an electric field on its surface with an approximately constant magnitude of 1.0 X 10 N/C directed toward the centre. U Til A (a) Compare Earth's electric field and gravitational field in terms of the fields' direction and shape, and how they change as the altitude increases. (b) Calculate the mass of a particle that can be suspended by Earth's electric field if the particle has the elementary charge on it.5. A 5.2 X 10- kg oil drop hangs between two parallel plates (Figure 3). 0.21 cm 220 V + + + + + + + +++ Figure 3 (a) Calculate the oil drop's charge. (b) Calculate the electron excess or deficit on the drop