`\[ F_{ \text{E} } ~=~ q \, E \]`

**Electric force \( F_{\text{E}} \)**SI unit: \( \text{N} ~=~ \frac{\text{kg} \, \text{m}}{\text{s}^2} \) (Newton)

It is the force that an electric charge experiences in an electric field. If you place a few charges (for example, electrons, protons) in an electric field, these charges are accelerated by the electric force! Depending on whether they are positive or negative charges, they are accelerated either in the direction of the electric field lines (positive charges) or in opposition to the electric field lines (negative charges).

**Electric charge \( q \)**SI unit: \( \text{C} ~=~ \text{As} ~=~ \frac{\text{kg} \, \text{m}^2}{\text{V} \, \text{s}^2} \) (Coulomb)

of a single particle, e.g. of an electron or proton.

The charge determines in which direction the electric force acts. Positive charges have the sign plus - the force acts in the direction of the electric field lines. That is true for example for protons, alpha particles or positively charged ions, such as \(\text {Na}^+ \). Negative charges have the sign minus - the force acts against the electric field lines. That is true for example for electrons.

An electron carries a *negative* charge \(q ~=~ -1.602 \cdot 10^{-19} \, \text{C} \). A proton carries a *positive * charge: \(q ~=~ +1.602 \cdot 10^{-19} \, \text{C} \). Negative charges have a minus before the value of the charge and positive charges have a plus.

**Electric field magnitude \( E \)**SI unit: \( \frac{\text V}{\text m} ~=~ \frac{\text{kg} \, \text{m}}{\text{A} \, \text{s}^3} \) (volt per meter)

tells you how much electric force acts on an electric charge. The fields magnitude is illustrated by field lines. The closer the field lines are to each other, the greater is the magnitude of the electric field, and the greater is the electric force acting on a charge there. The field lines show you in which direction the electric force is pointing. They can be straight, such as inside a plate capacitor. The force points always points in the same direction there. But they also can be bent; then the force would point in a different direction, depending on where you place the charge \(q \).

Rearrange the equation for the electric field: \( E ~=~ \frac{F_{ \text{E} }}{q} \), as you can see, it is "*Force per charge*".

During a thunderstorm, for example, a very high electric fields dominate between the earth and clouds; it reaches values above \(150 \, 000 \, \frac{\text V}{\text m} \).

The electric field magnitude which is generated by a charged particle (e.g., an electron) can be determined by Coulomb's law.