Questions

1. What are the units of electric field strength?

2. Sketch a diagram to show the electric field between parallel plates. Include arrows to show the direction of the field.

3. What force would act on a charge of 1.6 x 10-19C at a point where the electric field strength is 3 x 109 N/C

4. Given €0 = 8.85 x 10-12 F/m show that 1 / ( 4 pi €0 ) = 9 x 109

5. Calculate the repulsive force between two protons ( q = 1.6 x 10-19C ) which are 2 x 10-15m apart

6. The dome of a Van Der Graaf generator carries a charge of 50 x 10-6C. What force would a dust particle experience 50cm from its center if it carried a charge equivalent to 50 electrons.

7. a) Calculate the electric field strength at the surface of a metal sphere, of radius 20 cm,  which carries a charge of 200 x 10-3C.

b) Sketch a graph to show how the field strength varies from the surface of the sphere to a distance of 80 cm from its surface.
c) What force would act on a small particle carrying a charge of 5 x 10-9C at a point 80 cm from the surface of the sphere?

8. A 500V d.c. supply is connected across two parallel plates 20 cm apart.

a) Calculate the electric field strength between the plates
b) Sketch a diagram showing field lines and equipotentials between the plates
c) What electrical force would act on a particle which carries a charge of 5 x 10-9C between the plates?
d) How much electrical energy would be transferred if this charge moved from one plate to the other?

9. The potential difference between a cloud, 50m high, and the surface of the Earth is 500,00V

a) Calculate the electric field strength in the space between.
b) What electrical force would act on a raindrop in this space which carried an excess charge of 12.8 x 10-19C?

10. Considering a hydrogen atom to consist of a proton and an electron at an average separation of 0.5 x 10-10m, find

a) the electrical potential at 0.5 x 10-10m from the proton,
b) the potential energy of the electron,
c) the energy required to remove the electron from the atom assuming it is at rest
d) name another factor which should be considered when calculating the energy in part c)

11. A metal sphere of radius 15 cm carries a charge of 200 x 10-4C

a) Sketch how the electrical field strength varies with distance, r,  from the centre of the sphere from r = 15cm up to r = 45 cm.
b) On the same axes sketch how the potential due to the sphere varies over the same distance.