charge of the particle. Electric field is a vector; so, electric fields are always drawn as arrows.
Every point in an electric field has a certain value called, surprisingly enough, the “electric field
value,” or E , and this value tells you how strongly the electric field at that point would affect a charge.
The units of E are newtons/coulomb, abbreviated N/C.
Force of an Electric Field
The force felt by a charged particle in an electric field is described by a simple equation:
F = qEIn other words, the force felt by a charged particle in an electric field is equal to the charge of the
particle, q , multiplied by the electric field value, E .
An electron, a proton, and a neutron are each placed in a uniform electric field of magnitude 60 N/C,
directed to the right. What is the magnitude and direction of the force exerted on each particle?The direction of the force on a positive charge is in the same direction as the electric field; the
direction of the force on a negative charge is opposite the electric field.Let’s try this equation on for size. Here’s a sample problem:The solution here is nothing more than plug-and-chug into F = qE . Notice that we’re dealing with a
uniform electric field—the field lines are evenly spaced throughout the whole region. This means that, no
matter where a particle is within the electric field, it always experiences an electric field of exactly 60
N/C.
Also note our problem-solving technique. To find the magnitude of the force, we plug in just the
magnitude of the charge and the electric field—no negative signs allowed! To find the direction of the
force, use the reasoning in the box above (positive charges are forced in the direction of the E field,
negative charges opposite the E field).
Let’s start with the electron, which has a charge of 1.6 × 10−19 C (no need to memorize, you can look