Physics 9702 · AS & A Level · Electric force between point charges
Electric force between point charges — practice question
Two point charges A and B each carry a charge of $+6.4 \times 10^{-19}\,\text{C}$. They are in a vacuum and are separated by a distance of $12.0\,\mu\text{m}$, as illustrated in Fig. 4.1. Points P and Q lie on the line AB. Point P is $3.0\,\mu\text{m}$ from charge A, while point Q is $3.0\,\mu\text{m}$ from charge B.
(a)[3]
Calculate the repulsive force between charges A and B.
(b)[2]
Explain why, even without doing any calculation, moving a small test charge from point P to point Q results in zero net work done.
(c)[4]
Calculate the work done by an electron as it moves from the midpoint of line AB to point P.
Worked solution & mark scheme
This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Coulomb’s law is $F = \dfrac{q_1 q_2}{4\pi\varepsilon_0 x^2}$.” …