All charged objects produce a thing we call their electric field. It is not observable in the conventional sense and might be thought of as a clever way to keep track of how charged objects interact. The field from one electron can influence another electron and the result is they feel a repelling force.
Large electric fields are in the atmosphere during storms.
Watch the pre-lecture videos and read through the OpenStax text before doing the pre-lecture homework or attending class.
Point Charge
The electric field for a point charges points away from positive charges and towards negative charges. It's magnitude has an inverse square dependency on the distance from the charge. If you double your distance from the charge the field decreases by a factor of 4. All of this information is contained in the expression below.
Electric Field for a Point Charge
$\overrightarrow{E}_q(\overrightarrow{r}_p) = \frac{kq}{|\Delta \overrightarrow{r}|^2}\Delta \hat{r}$
The above equation reads that the electric field from charge $q$, at point $p$, is equal to a constant ($k=8.99 x 10^9 N m^2/C^2$) times the charge, divided by the square of the absolute value of the change in position from $q$ to $p$, multipled by the delta $r$ hat direction. The $\Delta \hat{r}$ is a unit vector, meaning it has magnitude of 1 and only provides a direction.
$\Delta \overrightarrow{r} = <\Delta{x}, \Delta{y}, \Delta{z}>$
$\Delta \hat{r} = < \frac{\Delta x}{|\Delta \overrightarrow{r}|}, \frac{\Delta y}{|\Delta \overrightarrow{r}|}, \frac{\Delta z}{|\Delta \overrightarrow{r}|}>$
Electric Field for a Point Charge Equation
Net Electric Field
The Electric Field due to an Infinite Sheet
Now, take a look at the pre-lecture reading and videos below.
OpenStax Section 18.5 | Electric Field Lines: Multiple Charges
