Electric Fields Flashcards
Coulomb's law, electric field strength, electric potential.
State Coulomb’s law.
The force between two point charges is proportional to the product of the charges and inversely proportional to the square of their separation.
(Must mention point charges)
Formula for Coulomb’s law
Check notes.
Define electric field strength.
Force per unit positive charge.
Formulae for electric field strength.
E = F/q
and
check notes for the other formula.
Define electric potential.
Work done per unit charge in moving a positive charge from infinity to the point.
Formula for electric potential.
Check notes.
What is the electric potential at infinity?
0
The potential near a positive charge is positive. Why?
When a unit positive charge is moved from infinity towards another positive charge, work is done by the external force on the unit charge because the electric force between the charges is repulsive.
The potential near a negative charge is negative. Why?
When a unit positive charge is moved from infinity towards a negative charge, work is done by the attractive electric force.
Define electric potential energy.
The work done in bringing a positive charge from infinity to the point.
Formula for electric potential energy.
Check notes.
State the relationship between electric field strength and potential.
The electric field strength is equal to the negative potential gradient.
Formula which shows the relationship between electric field strength and potential.
See notes.
The electric field strength is equal to the negative potential gradient.
What does the minus sign indicate?
The minus sign indicates that the direction of the electric field is the same as the direction of decreasing potential.
Similarities between gravitational fields and electric fields.
(a) Gravitational force is inversely proportional to the square of the separation of masses.
Electric force is inversely proportional to the square of the separation of charges.
(b) Gravitational field strength is force per unit mass.
Electric field strength is force per unit positive charge.
(c) Gravitational potential is the work done in moving a unit mass from infinity to the point.
Electric potential is the work done in moving a unit positive charge from infinity to the point.
(d) Gravitational potential and electric potential is zero at infinity.
