Electric Fields (Module 22) Flashcards
What is an electrical conductor?
A metal that contains lots of free electrons. (Electrons that are not attached to any one atom).
Finish this sentence: An electrically insulating material _____
does not contain free electrons.
What does the gold leaf electroscope detect?
Charge
Define a line of force (or a field line).
A path that a free positive test charge follows.
Define electric field strength.
At a point in a field is defined as the force per unit charge on a positive test charge placed at that point.
What is the unit for electric field strength?
NC^-1 (Newton per Coulomb), It can also be Vm^-1 (Volt per Metre).
Knowing the units from the previous question, what formulae can be derived from those units?
E = F/Q and E=V/D
Define electric potential.
It is a point in an electric field that the work done per unit charge on a small positively charged object is required to move it from infinity to that point within the field
What is the unit of electric potential?
The unit is volt (equal to 1 JC^-1)
What is an equipotential?
These are surfaces of constant potential. Therefore a test charge moving along an equipotential surface has constant potential energy.
Define potential gradient.
The potential gradient at any position in an electric field is the change of potential per unit change of distance in a given direction.
Finish this sentence: The electric field strength is equal to the negative of the _______
potential gradient.
What is Coulomb’s law of force?
For two points charges Q1 and Q2 are at distance apart r, the force F between the two charges is given by his equation (F=(Q1Q2)/(4PIE0R^2)) where E0 is the permittively of free space.
Name one of the three main differences between a gravitational field and a electrostatic field.
- There forces
- There action at a distance (Masses or charged objects)
- There constant of proportionality in the force law
