State an equation for the electric field strength $E$ at distance $r$ from a point charge $Q$ in a vacuum. Also give the name of any other symbol used.
Two point charges A and B are separated by $10.0\,\text{cm}$ in a vacuum, as shown in Fig. 6.1. A point $P$ lies on the straight line joining A and B. Point $P$ is at distance $x$ from A. Figure 6.2 shows how the electric field strength $E$ at $P$ changes with $x$.
State and explain whether charges A and B have equal signs or opposite signs.
State and explain whether charges A and B have the same magnitude or different magnitudes.
An electron is placed at point $P$. Without doing any calculation, state and explain how the size of the electron’s acceleration changes as it moves from the position where $x = 3\,\text{cm}$ to the position where $x = 7\,\text{cm}$.