Question

The electric field due to an infinitely long straight uniformly charged wire at a distance $r$ is directly proportional to

• A. r
• B. $r^{2}$
• C. $\frac{1}{r}$
• D. $\frac{1}{r^{2}}$

Answer 1

Answer: (C)

The electric field due to an infinitely long straight uniformly charged wire at a distance r is
$E=\frac{\lambda}{2\pi\varepsilon_{0} r}$
where $\lambda$ is the uniform linear charge density and $\varepsilon_{0}$ is the permittivity of free space.
$\therefore \, E \propto \frac{1}{r}$