3.7.3 - Electric Fields Flashcards
Where can charge be assumed to act?
at the centre of the sphere
What can we treat air the same as when using the electrostatic force equation?
a vacuum
What force is the magnitude of electrostatic force between subatomic particles greater than? Why?
the magnitude of gravitational forces
the masses are very small but the charges are much bigger
When is a uniform field formed?
Between two parallel charged plates
What does the electric field around a negative charge look like?
straight lines with arrows pointed towards the centre of the sphere
What does the electric field around a positive charge look like?
straight lines with the arrows pointed away from the centre of the sphere
What does the electric field between two parallel (+ve and -ve) plates look like?
Straight lines hitting the plates perpendicular, arrows going towards the -ve plate
What does the magnitude of electric force depend on in a radial field?
the distance between the two charges
How do we find out the charge of a particle?
Using two parallel plates (one +ve and one -ve), fire the particle at right angles to the field and observe the path. A charge particle will experience a constant electric force, causing it to accelerate to follow a parabolic shape towards the plate with an opposite charge.
When is the magnitude of electric potential is greatest?
at the surface of the charge
When is electrical potential at 0
at infinity
When is potential positive? Why?
When the charge is positive
work is done against the field since there is a repulsive force
When is potential negative? Why?
When the charge is negative
work is done by the field due to the attractive force
What is the gradient of a potential against distance graph equal to?
electric field strength, E
What happens when moving along an equipotential?
No work is done
What do equipotential surfaces look like between two parallel charged plates?
parallel to the plates
What do the equipotential surfaces around a point charge look like?
concentric circles
What is the area under the graph equal to on a graph of electric field strength against distance
the electric potential difference
What is unique about electric field strength?
it’s a property of the field at that point - not affected by the moving small test charge
What is an electrical conductor? What does this mean (field lines)?
an equipotential surface
field lines always meet conductors at right angles
Why is the time taken for an object to free fall independent of its mass?
F=mg and a=F/m sp the acceleration is always = g. Time to fall a given distance depends only on the distance and acceleration (due to gravity).
