Question

An electron is placed on $X$ -axis where the electric potential depends on $x$ as shown in figures (the potential does not depend on $y$ and $z$ ). What is the electric force on the electron ?

• A. $4.0\times 10^{-18}N$
• B. $8.0\times 10^{-18}N$
• C. $3.2\times 10^{-16}N$
• D. $4.0\times 10^{-16}N$

Answer 1

Answer: (D)

From the graph, given in the question
The slope of the electric potential versus distance graph
$\frac{dv}{dx}=\frac{-500}{20\times 10^{-2}}V/m$
$=-2.5\times 10^{3}V/m$
Since, we know that
Electric field, $E=-\frac{dv}{dx}$ (at a point)
$E=2.5\times 10^{3}V/m$
$\therefore$ The electric force on the electron at that point
$F=eE$
$=1.6\times 10^{-19}\times 25\times 10^3$
$=4\times 10^{-16}N$