Electric Fields

Field lines begin on positive charges and end on negative charges.

The direction of the electric force on a negative charge is opposite to the direction of the positive one.

• Electric Fields are caused by charges of objects in proximity to one another. 
• The magnitude of the electric field depends on the magnitude of the charge of the objects.
• magnitude also depends on the distance from the charged source causing the field
• a charged object when placed into an electric field experiences an electrical force

Below is a drawing of an electric field with the formula for finding an electric field. The electric field is the force per unit of charge.

Here we solved for the total electric field from two different points using the formula for the electric field and Coulomb's Law.

Below is an integral showing how to find the formula for an electric field across a line.

Electric dipole moments are the product of the magnitude of the charge and the distance of separation between the charges.

• Given a pair of plates, one of which is positively charged and the other is negatively charged
• an electron is fired horizontally between the two plates
• similar to projectile motion
• can use kinematics for certain problems

The work done by a dipole moment is found using torque and the angle of rotation.

The potential energy is found through the dipole moment vector and the electric field.

An electric field displayed using V-Python is different from a real electric field. The program depicts horizontal lines and no lines at an angle.

Summary:

• The electric field vector at a point in space is defined as the electric force. 
• Direction of an electric field vector in space is the same direction that a small positive charge would move if placed at the location.
• Electric field at some point in space can be thought of as being detached from the charges from which the electric field originates. 
• The direction of the electric force on a negative charge is opposite to the direction of the electric field.
• There is an infinite number of field lines surrounding a charge.
• The electric field at a particular point in space is equal to the vector sum of the electric fields.