(b) This graph shows the electrical potential near an antiproton.

(ii) Determine the potential energy a positron would have at this distance.

This diagram shows a conducting sphere of radius $0.80 \mathrm{cm}$ carrying a charge of $+6.0\times {10}^{-8}\mathrm{C}$ resting on a balance.

Calculate the electric field at the surface of the sphere.

This diagram shows a conducting sphere of radius $0.80 \mathrm{cm}$ carrying a charge of $+6.0\times {10}^{-8}\mathrm{C}$ resting on a balance.

(b) An identical sphere carrying a charge of $-4.5\times {10}^{-8}\mathrm{C}$ is held so that its centre is $5.0 \mathrm{cm}$ vertically above the centre of the first sphere.

(i) Calculate the electric force between the two spheres.

This diagram shows a conducting sphere of radius $0.80 \mathrm{cm}$ carrying a charge of $+6.0\times {10}^{-8}\mathrm{C}$ resting on a balance.

(b) An identical sphere carrying a charge of $-4.5\times {10}^{-8}\mathrm{C}$ is held so that its centre is $5.0 \mathrm{cm}$ vertically above the centre of the first sphere.

(ii) Calculate the new reading on the balance.

This diagram shows a conducting sphere of radius $0.80 \mathrm{cm}$ carrying a charge of $+6.0\times {10}^{-8}\mathrm{C}$ resting on a balance.

(c) The second sphere is moved vertically downwards through $1.5 \mathrm{cm}$. Calculate the work done against the electric field in moving the sphere.