Post on 18-Jan-2016
The Electric FieldA region where a charged particle
experiences an electrical force.
Coulomb’s Law
+ +
F F
q q1
21
r
)(q)(qkF
Electric Field Equation Derivation
+ +F F
q
qo
2o
r
)(q)(qkF
2o r
qk
q
F
The Electric Field Equation
2r
qkE
+r
The electric field at a distance r from charge q.
q+
qo
E
F
oq
FE
The electric field at qo’s location due to the electricalforce exerted on qo.
The electric field strength is the same using both methods of calculation.
Consider the equation yielded by multiplying E by qo.
• The electric field is a vector quantity.
• The electric field is measured in Newton/Coulomb (N/C) and Volts/meter (V/m).
• The electric field represents the force per unit charge on a charge in the field.
• The electric field is defined by the direction a small positive, test charge would move if placed in the field.
• Positive charges always move in the direction of the electric field and negative charges in the opposite direction to the electric field.
The Analogous Relationship of Electric Field to a Mechanical System
2r
MGg
oq
FE
2r
qkE
m
Wg
The gravitational field at location r caused by mass M.
The weight (gravitational force)exerted on mass m, caused bygravity.
The electric field at location r caused by charge q.
The electrical force exerted on charge qo, caused by the electricfield.
The Force on a Charge in an Electric Field
• Fe=qE
• Fe – the electrical force on the charge
• q - the charge in the electric field
• E - the electric field
• W=mg
+ +
qoq
Electric Field Lines Derivation
+ qo
The Electric Field Lines Surrounding a Positive Charge
+
The Electric Field Lines Surrounding a Negative Charge
-
Electric Field Vectors
+
Some Various Electric Field Configurations
• A small positive test charge will follow the field lines.
The Electric Field Between Parallel Plates
+ + + + + + + + + + + + +
- - - - - - - - - - - - - - - -
•The electric field is uniform in this situation.
Parallel plates – two parallel sheets of equal quantity and opposite charges on each plate.
•This is analogous to the gravitational field being uniform near the surface of a planet.