Which statement best describes the Electric Field?

Which statement best describes the Electric Field?

• A. It is a vector field describing the force on a unit charge in space.
• B. It is a scalar field representing energy per unit charge.
• C. It is the rate at which energy is transmitted by radiation.
• D. It is the propagation speed of electromagnetic waves.

Answer: (A)

Electric field is a vector field that assigns to every point in space a vector describing the force a small positive test charge would experience there, per unit charge. In other words, the force on a test charge q is F = qE, so E = F/q in the limit of a tiny charge. Because it has both magnitude and direction, it’s a vector quantity, pointing in the direction a positive test charge would accelerate. The magnitude falls off with distance from sources and depends on the arrangement of charges. The other statements describe different concepts: energy per unit charge would be electric potential (a scalar), not the field; the rate at which energy is transmitted by radiation relates to energy flux (not the field itself); and the propagation speed of electromagnetic waves is the speed of light, not the defining feature of the electric field at a point.

Electric field is a vector field that assigns to every point in space a vector describing the force a small positive test charge would experience there, per unit charge. In other words, the force on a test charge q is F = qE, so E = F/q in the limit of a tiny charge. Because it has both magnitude and direction, it’s a vector quantity, pointing in the direction a positive test charge would accelerate. The magnitude falls off with distance from sources and depends on the arrangement of charges. The other statements describe different concepts: energy per unit charge would be electric potential (a scalar), not the field; the rate at which energy is transmitted by radiation relates to energy flux (not the field itself); and the propagation speed of electromagnetic waves is the speed of light, not the defining feature of the electric field at a point.