ELECTRIC FIELDS

I. The electric field at a point is space is defined as: E = limq0->0 (F/q0) where q0 is a small positive test charge located at that point and F is the force on that charge.







II. Field lines are often used as a pictorial representation for an E-field.

    A. Originate on (+) charges and end on (-) charges

    B. Number of lines at each charge is proportional to the size of the charge.

    C. Electric field is tangent to the field line.





III. A dipole consists of a two point charges of the same magnitude but opposite signs and closely spaced to each other.









Examples

1. Two opposite charges (magnitude = 0.20 microcoulombs) are held 0.15 m apart. What is the magnitude and direction of E midway between them?









2. A thin nonconducting rod of length L has a charge q uniformly spread along it. Find the magnitude E of the electric field at a point P which is a distance y away from the rod on the perpendicular bisector.