Question

A proton is placed at point $B$ between two electrons at points $A$ and $C$. The distance from point $B$ to point $C$ is twice the distance from point $B$ to point $A$. The force experienced by the proton is :

• A. Two times stronger from the electron at $A$
• B. Three times stronger from the electron at $A$
• C. Four times stronger from the electron at $A$
• D. The same from both electrons
• E. It is not possible to determine the force the proton experiences from the information provided

Answer 1

The correct option is C Four times stronger from the electron at $A$

Let the distance between A and B be $r$.

$\therefore$ Distance between between B and C be $2r$.

Coulomb force on proton by electron at A, $F_A=K\frac{q^2}{r^2}$ where $K=\frac{1}{4\pi {ϵ}_o}=constant$

Coulomb force on proton by electron at C, $F_C=K\frac{q^2}{(2r{)}^2}=\frac{K{q}^2}{4r^2}$

$⟹$ $F_A=4F_C$

Thus force experienced by proton is four times stronger from electron at A.