7.3 Electric fields Flashcards
What do electrical conductors contain a lot of?
Free electrons.
What do electrically insulating materials not contain?
Free electrons.
What are free electrons?
Electrons which move about inside the metal and are not attached to any one atom.
What happens when a charged conductor is connected to the Earth?
Charge neutralised by electrons transfer between the conductor and the Earth.
What is the magnitude of electrical force between two point charges?
(aka Coulomb’s law)
What do the letters represent in this equation?
What is the permittivity of free space?
A measure of the ablility of a vacuum to allow an electric field to pass through it.
For subatomic particles, which force is stronger gravity or electrostatic?
Electrostatic
Electric field lines go from what type of charge to what type of charge?
From positive to negative.
Draw an uniform electrical field.
Draw two radial electric fields one around a negative charge and the on around a positive charge.
Define electrical field strength.
Force per unit charge exerted on a test charge within the field.
What is the magnitude of electrical field strength in a uniform field?
What do the letters represent in this equation?
What is the magnitude of electrical field strength in a radial field?
What do the letters represent in this equation?
What is the work done moving a charge between a pair of parallel plates?
What do the letters represent in this equation?
What is the trajectory of a particle entering a uniform field at right angles?
Parabolic.
(Like projectile motion)
Define electrical potential.
The work done per unit charge, moving a test charge from infinity to a specific point.
Define electrical potential difference.
The difference in the electrical potential at two points in an electric field.
What is the work done when moving a charge in an electric field?
Is work done when moving a charge along an equipotential surface?
No.
(Since the potential difference is zero)
Draw an uniform electric field with equipotentials.
Draw two radial electric fields with equipotentials one around a negative charge and the on around a positive charge.
What is the equation for electric potential in a radial field?
What do the letters represent in this equation?
Define electrical potential energy.
Component of a charge’s energy due to its position in an electric field.
What is the electric potential energy?
What do the letters represent in this equation?
Draw the graph of electrical potential vs distance of a positive charge.
(Potential hill - Repulsive force)
Draw the graph of electrical potential vs distance of a negative charge.
(Potential well - Attractive force)
What does the gradient of an electric potential vs distance graph represent?
Electric field strength at a specific point.
Draw the graph of the magnitude of the electric field strength vs distance of a charge.
What does the area of an electric field strength vs distance graph represent?
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.
How is the potenital gradient effected if the field is non-uniform?
- Varies according to position and direction
- Closer equipotentials are, the greater the potential gradient is at right angles to the equipotentials
