The Physics
Hypertextbook
Opus in profectus

Electric Field

Summary

• Field
• A field is…
• a physical quantity that has a value for each point in space and time
• a mathematical function that returns a value for each point in space and time
• a way to deal with philosophical arguments against action at a distance
• Fields can be…
• scalar fields (temperature, pressure, density, electric charge, etc.)
• vector fields (wind velocity, fluid flow, etc.)
• force fields go with non-contact forces (gravitational field, electric field, magnetic field)
• Electric Field
• Magnitude  E = FE q
Where…  E = magnitude of electric field (electric field strength) Fg = electric force on test charge q = charge of test charge
• Units  ⎡⎣ N = V ⎤⎦ C m
• Direction
• Electricity is described by a vector field.
• The direction of the electric field at any point in space is the direction of the net electric force on a "small" positive test charge.
• The electric field around a spherically symmetric charge is radial and…
• diverges from positive charge
• converges on negative charge
• Use vector addition to find the net electric field when more than one charged object is present.
• Field lines never intersect.
• Strength
• Electric field strength is proportional to line density.