1.1. Fig. 20.1 shows a positively charged metal sphere and a negatively charged metal plate.

Fig. 20.1

On Fig. 20.1, draw a minimum of five electric field lines to show the field pattern between the sphere and the plate.

[2]

1.2. Define electric potential at a point in space.

[1]

1.3. A metal sphere is given a positive charge by connecting its surface briefly to the positive terminal of a power supply. The electric potential at the surface of the sphere is + 5.0 kV. The sphere has radius 1.5 cm.

i) Show that the charge Q on the surface of the sphere is 8.3 × 10⁻⁹ C.

[2]

ii) Fig. 20.2 shows the charged sphere from (i) suspended from a nylon thread and placed between two oppositely charged vertical plates.

Fig. 20.2 (not to scale)

The weight of the sphere is 1.7 × 10⁻² N. The string makes an angle of 4.0° with the vertical.

1. Show that the electric force on the charged sphere is 1.2 × 10⁻³ N.

[1]

2. Calculate the uniform electric field strength E between the parallel plates.

E = ................................... N C⁻¹ [2]