Answer to Question #132956 in Electricity and Magnetism for Alfraid

Question

Write electric field due to point charge.

Answer 1

We know that according to Coulomb's law the electrostatic force between two charges q₁ and q₂ is

$F = k_e\dfrac{q_1q_2}{r^2}$ , where r is the distance between two charges. If we take the direction of force into account, we get $\vec{F} = k_e \dfrac{q_1q_2}{r^3}\vec{r}$ . Here k_e is the Coulomb's constant (~8.99×10⁹ N⋅m²⋅C⁻²).

The electric field of the charge q₁is

$E = \dfrac{F}{q_2} = k_e\dfrac{q_1}{r^2}$ . If q₁ is positive, the direction of the field is "from q₁", if it is negative, the direction is "towards q₁".