State the meaning of electric potential at a point.
The centres of two charged metal spheres A and B are $44.0\,\text{cm}$ apart, as shown in Fig. 7.1. A movable point $P$ lies on the line joining the centres of the two spheres. Point $P$ is at a distance $x$ from the centre of sphere A. The graph in Fig. 7.2 shows how the electric potential $V$ at point $P$ varies with distance $x$.
Using Fig. 7.2, state and explain whether the two spheres carry charges of the same sign or opposite sign.
A positively charged particle is initially at rest on the surface of sphere A. It then moves freely from the surface of sphere A to the surface of sphere B. Describe qualitatively how the speed of the particle, if at all, varies with distance $x$ as it travels from $x = 12\,\text{cm}$ to $x = 25\,\text{cm}$, passes through $x = 26\,\text{cm}$, travels from $x = 27\,\text{cm}$ to $x = 31\,\text{cm}$, and arrives at $x = 32\,\text{cm}$.
The particle has charge $3.2 \times 10^{-19}\,\text{C}$ and mass $6.6 \times 10^{-27}\,\text{kg}$. Calculate the maximum speed of the particle.