The electric field is a vector quantity represented by an arrow whose length is proportional to the strength of the electric field and whose direction is parallel to that of the electric field, evaluated at the point where the tail of the arrow is located.
There are only three parameters to keep in mind when figuring out the strength and direction of the electric field at a point due to the influence of a nearby electric charge; the polarity of the charge (positive or negative), the magnitude |q| of the charge, and the distance r between the point charge and the location where the electric field is being evaluated.
The strength of the electric field (the length of the arrow representing the field) is directly proportional to |q| and inversely proportional to r2. The electric field points directly away from a positive point charge and directly towards a negative charge. In a situation involving more than one point charge, the calculation of the field involves simply the linear superposition of the individual contributions from each point charge considered separately. This is an extremely important point to understand in order to complete this lab.
Note: in this lab, we will assume the constant k in Coulomb's Law is equal to one.
In the first part of this lab you will analyze the electric field associated with individual point charges, and then you will analyze the electric field associated with specific arrangements of two or more point charges by using the superposition principle.
Electric field lines are useful for visually estimating the magnitude of an electric field in some region, as opposed to calculating it for a single location. As we have noticed in the previous lab and in general, electric field vectors are directed toward negative charges and away from positive charges (a positive "test" charge would repel from the positive charge and attract to the negative). To illustrate the linear proportionality of the charge magnitudes, we will draw a multiple of field lines around the charge, equally spaced. In reality, there are an infinite number of field lines around a charge (as we can certainly determine the field at any point around the charge), so what we're really doing is creating a 2D topographical map, with differences in the field magnitudes shown by differences in line density.
A reasonable proportionality factor is at least 4; that is, a charge of +1 would have 4 equally-spaced field lines drawn radially outward from its center. When drawing lines between multiple charges, be sure to converge (connect) lines between opposite charges and diverge (spread out) lines between like charges. When dealing with conductors whose surfaces (which contain freely moving charges- electrons!) are capable of conducting, or re/directing electronic flow, lines which terminate or originate at nearby charges will then originate or terminate respectively perpendicularly at the conductor's edge.
Note that the Data Sheets below are for use during the lab sessions, and the Lab Report are for the more reflective reporting of what you have learned from each experiment. You only need to submit the Lab Report for this lab.