Explain the electric field lines and the magnitude of electric field.

Pictorial representation of electric field produced by charge or system of charges is electric field lines.

Draw vectors pointing along the direction of the electric field with their lengths proportional to the strength of the field at each point.

Since the magnitude of electric field at a point decreases inversely as the square of the distance of that point from the charge, the vector gets shorter as one goes away from the charge always pointing radially outward (if charge is positive then outwards and if it is negative then inwards) $\mathrm{E}=\frac{k \mathrm{Q}}{r^{2}}$

In this figure, each arrow indicates the electric field i.e. the force acting on a unit positive charge placed at the tail of that arrow. Connect the arrows pointing in one direction and the resulting figure represents a field line.

The magnitude of the field is represented by the density of field lines.

$\overrightarrow{\mathrm{E}}$ is strong near the charge, so the density of field lines is more near the charge and the lines are closer. Away from the charge, the field gets weaker and the density of field lines is less, resulting in well-separated lines.