Chapter 22 - Electric Fields Flashcards
(10 cards)
Which direction do the field lines point around a positive charge?
Away from the charge.
Define electric field strength.
The force experienced per unit positive charge at a point in an electric field.
State Coulomb’s law.
The force that two point charges exert on each other is directly proportional to the product of their charges, and inversely proportional to the square of their separation.
Describe the main differences between electric & gravitational fields.
-Gravitational forces are always attractive, but electric fields can be attractive or repulsive.
-Objects can be shielded from electric fields but not gravitational fields.
-The size of an electric force depends on the medium between charges, but this makes no difference to gravitational fields.
What is the relative permittivity of a material?
A ratio of the size of an electric field generated in a vacuum, compared to if it was generated in that material.
How is the permittivity of a material calculated if you have the relative permittivity?
ε = εᵣ × ε₀
Outline an experiment to determine the permittivity of free space (ε₀).
-Connect a capacitor with a known separation to a power supply of a known P.D.
-Discharge the capacitor through a coulombmeter.
-Repeat with varying P.D.s.
-Plot a graph of V against Q.
- ε₀ = 1/(4πr(gradient))
How does a charged particle move in a uniform electric field?
It experiences a constant acceleration in one direction, its movement can be predicted using the uniform acceleration (suvat) equations.
Define electric potential.
The work done per unit positive charge required to bring a charge from infinity to a point in an electric field.
What is the area under a force-distance graph for two point charges?
The work done to increase/decrease the separation of the two point charges.
