# Question #89b77

Oct 4, 2017

The 'line' is an arrow, meaning the field is a vector.

#### Explanation:

A vector has both size (or magnitude) and direction. As a field can point in different directions this information is also important.

Oct 4, 2017

The equation says that the electric field $\vec{E}$ is the following quotient: (the force, ${\vec{F}}_{E}$, due to the electric field, on a test charge) divided by (the charge, q, of the test charge).

#### Explanation:

The definition of electric field from my copy of $H a l l i \mathrm{da} y \cdot R e s n i c k \text{ Physics Part II}$:

If a positive test charge ${q}_{o}$ is placed at point P and if an (electric) Force F acts on the stationary charge, an electric field E is present at P, where E is the vector satisfying the relation
F = ${q}_{o}$ E

The Equation of the pic you included, with your symbols, is
$\vec{E} = {\vec{F}}_{E} / q$.
That equation is equivalent to the equation above from my college textbook.

• The $\vec{E}$ is the electric field. The units of $\vec{E}$ are Newtons/Coulomb.
• The ${\vec{F}}_{E}$ is the force that acts on a test charge due to the electric field it finds itself in. The unit of ${\vec{F}}_{E}$ is Newtons.
• The $q$ is the charge on the test charge. The unit of q is Coulombs.

I hope this helps,
Steve