Problem — Electric field at 30 cm

Problem

Calculate the magnitude of the electric field at $30\ \text{cm}$ from a point charge $q = +5\ \mu\text{C}$ in vacuum.

Solution

Data. $q = 5\cdot 10^{-6}\ \text{C}$, $r = 0{,}30\ \text{m}$.

Field of a point charge.

$E = k\,\frac{q}{r^2} = 8{,}99\cdot 10^9 \cdot \frac{5\cdot 10^{-6}}{(0{,}30)^2} = \frac{44950}{0{,}09} = 4{,}99\cdot 10^5\ \text{V/m}$

The field points radially outward (positive charge).

$\ev{E \approx 5\cdot 10^5\ \text{V/m}}$

Links

Topics: Electric field and potential Concepts: Electric field