Electric Fields Flashcards
(32 cards)
Define Coulomb’s law
The magnitude of the force between two point charges in a vacuum is directly proportional to the product of their charges and inversely proportional to the square of the distance between the charges
Describe the force on two charges in terms of magnitude
Force on Q1 is equal and opposite to the force on Q2
Explain the difference between the magnitude of electrostatic forces between subatomic particles than the magnitude of gravitational forces
Electrostatic forces are much greater as they’re charges a much larger than they’re small masses
Define electric field strength
The force per unit positive charge
What is the general equation for gravitational field strength
E = F / Q
What is the equation for gravitational field strength in a uniform field
E = V / d
V is the potential difference across the plates
D is the distance between the plates
Describe a uniform field
Exerts the same electric force everywhere
Write the derivation to calculate formula for the wrok done by moving a charged particle between the parallel plates in a uniform field
- equate E = F / Q And E = V / d
- remember Fd is work done
Describe the forces acting on a charged particle that enters a uniform field at right angles
Experiences a constant force parallel to the field lines
Describe the effect of the force acting on a charge particle moving at right angles to a uniform electric field
Causes particle to accelerate at right angles to its original motion, so follows a parabolic shape
Describe the direction a force acts for a positive charge in a uniform field
Force acts in the same direction as the field, so positive charge follows the direction of the field
Describe the direction a force acts on a negative particle in a uniform electric field
Force acts in the opposite direction to the field line, so negative charge moves in the opposite direction to the direction of the field
Define absolute electric potential at a point
The potential energy per unit charge of a positive point charge at that point
Where is the absolute magnitude of electric potential greatest
At the surface of the charge
What is the value electric potential at infinity
Zero
What do all point in an electric field have
An absolute electric potential
What does the sign on the charge determine
Whether the value of potential in negative or positive
What does the value of potential ( negative or positive ) depend on
The sign of the charge
Describe the potential for an attractive force
Potential is initially negative, so tends so zero as r reaches infinity
Describe the potential for a repulsive force
Potential is initially positive and tends to zero as r reaches infinity
How do find the electric field strength at a point on a graph
Find the gradient of the tangent at that point on graph of V against r
What is the gradient of a tangent on graph of V against r
Electric field strength at that point
Define electric potential difference
The energy needed to move a unit charge between 2 points
Where does electric potential arise
Between 2 points in an electric field with different electric potentials
