Page 383 - Physics Coursebook 2015 (A level)

Chapter 23: Coulomb’s law
9 Figure 23.22 shows a conducting sphere of radius 0.80 cm carrying a charge of +6.0 × 10−8 C resting on a balance.
conducting sphere
insulating stand balance
Figure 23.22 For End-of-chapter Question 9.
a Calculate the electric field at the surface of the sphere. [2]
b An identical sphere carrying a charge of −4.5 × 10−8 C is held so that its centre is 5.0 cm vertically above
the centre of the first sphere.
i Calculate the electric force between the two spheres. [2]
ii Calculate the new reading on the balance. [1]
c The second sphere is moved vertically downwards through 1.5 cm. Calculate the work done against
the electric field in moving the sphere. [3]
mN
371