Electric Fields Flashcards
Define a field
A field is a region in which a body can experience a non-contact force.
What are the rules for drawing electric field lines?
When drawing electric fields:
The lines should never cross
The spacing of the lines represents the strength of the field
An arrow should be drawn to show the direction of force that a positive charge would feel
What is a field line (electric)?
The path a free positive test charge follows.
Describe a field between two oppositely charged plates
Field lines run parallel
At right angles to the plates
At the edges of the field the lines are slightly curved
What kind of a field is it between two oppositely charged plates?
Uniform field
Define electric field strength at a point in the field
The force per unit charge on a positive test charge placed at that point.
Electric field strength between plates is proportional to what?
Q/A
Q - charge
A - surface area
Define electric potential at a point in an electric field
Work done per unit positive charge on a positive test charge when it is moved from infinity to that point.
Define potential gradient (electric) at a point in an electric field
The change of potential per unit change of distance in a given direction.
How is potential gradient effected if the field is non-uniform?
Varies according to position and direction.
Closer equipotentials means greater potential gradient at right angles to them.
How is potential gradient effected if the field is uniform?
Equipotentials between the plates are equally spaced parallel to the plates.
Potential gradient is constant.
Define electric field strength
The negative of the potential gradient.
Define Coulombs law
The force of attraction or repulsion between two charges is proportional to the product of the masses and inversely proportional to the separation squared.
What is a point charge?
An expression for a charged object in a situation where distances under consideration are much greater than the size of the object.
If two forces are in the same direction, what is the resultant electric field strength formula?
E(1) + E(2)
If two forces are in opposing direction, what is the resultant electric field strength formula?
E(1) - E(2)
If two forces are at right angles to each other, what is the resultant electric field strength formula?
Resolve using pythagorus.
sqrt(E(1)^2 + E(2) ^2)
What can be found from a graph of force against separation?
Area = work done = Electrical potential energy
What can be found from a graph of electric field strength against separation?
Area = Electrical potential
What can be found from a graph of electric potential against separation?
Gradient = Electric field strength
