Download Electric Field - General Physics - Lecture Notes and more Study notes Physics in PDF only on Docsity!
Electric Field: Field produced by a single or group of charges that permeates all space.
Fields are responsible for creating forces at a distance on objects (Examples: gravitational and electric fields)
Electric Field Strength = positive test charge
Force onpostive test charge
q
E F SI unit: Newtons/Coulombs (N/C)
The electric field is a vector quantity whose magnitude is the force per unit charge and points in the direction of the force on the positive test charge.
The electric field direction is radially outward from a positive charge and radially inward toward a negative charge.
Force directions on point charges in space (E due to charge +q). E
E
E
+q
-q
F
F
Electric Field from charge Q:
^2
E kQ r where 9 2 2 k 9.0x10 N m C
(two significant figures)
SI units for Electric Field: Newtons/Coulombs [N/C]
Electric Field Lines (lines of force) - indicate direction of force on a positive test charge from a distribution of charges. The electric field points in the direction tangent to the field at any point.
Electric field lines point radially outward for a positive point charge and radially inward for a negative point charge.
The number of lines entering (leaving) a charge is proportional to the magnitude of the charge. (Example: a charge of +2q will have twice as many lines leaving as a charge of +q).
Lines closer together indicate stronger electric fields.
Total Electric Field at a point, P, in space is the vector sum of all fields resulting from charges ( Superposition of Fields )
1 2 3
E E E E
In good metallic conductors:
(i) static electric fields are not present (zero) (ii) charges reside on the surface (iii) electric field is perpendicular to the surface
In good metallic conductors:
(i) static electric fields are not present (zero inside a conductor) (ii) charges reside on the surface
(iii) electric field is perpendicular to the surface ( =
E )
Electric Flux: Electric field lines passing through an area.
E EA cos E A EA
