Electric Fields Flashcards
What is an electric field associated to?
Charge
Define electric field strength
The force that would act on a unit charge placed at a point in the field.
What is the relationship between electric field strength and the distance?
E ∝ 1/r^2
What is the pattern of electric field lines?
Radial
What is the direction of an electric field?
The direction of the force that would act on a positive charge placed in the field.
Give two factors that can affect the size of the electric field between two plates.
- The pd across the plates.
- The plate separation.
What is the relationship between electric field strength and the position between the plates?
They are independent
What is the relationship between electric field strength and the pd across the plates?
E ∝ V
What is the relationship between electric field strength and the separation of the plates?
E ∝ 1/d
When does the formula E=V/d apply?
When two plates are parallel
When does an electric field do work on a positive charge?
When the charge moves in the direction of the electric field.
What is the relationship between electric field lines and equipotential surfaces?
They are perpendicular to each other.
What is the relationship between field strength and potential?
Field strength = -Potential gradient (-dV/dx)
What is the relationship between potential and charge?
V ∝ Q
What is the relationship between potential and distance?
V ∝ 1/r
How is potential calculated?
V = (1/4πε0)(Q/r)
What is ε0?
The permittivity of free space
How is the potential at the surface of a sphere calculated?
V = (1/4πε0)(Q/a)
How is electrical potential energy calculated?
EPE = qV
What does a negative EPE show?
An attractive system
How is electric field strength in a radial field calculated?
E = (1/4πε0)(Q/r^2)
How is the force between two objects calculated?
F = (1/4πε0)(Qq/r^2)
Is field potential scalar of vector?
Scalar
Is field strength scalar or vector?
Vector
What is the unit of W?
Joules
When is work done by the field?
When W is negative
When is work done against the field?
When W is positive
How is work done calculated?
W = qΔV
How is the force on a charge in an electric field calculated?
F = qE
When is the force of an electric field positive?
When the force is repulsive
When is the force of an electric field negative?
When the force is attractive
What type of shape will an electron moving through an electric field produce?
A parabola going towards the positive plate.
What is Coulomb’s Law?
F = (1/4πε0)(Q1Q2/r^2)
How is electric field strength calculated?
E = F/Q
How is electric field strength in a uniform field calculated?
E = V/d
