Electrostatics

Question 1

State Coulomb’s law

Answer 1

Two point charges in free space or air exert forces on each other. The force is directly proportional to the product of the charges and inversely proportional to the square of the distance between the charges
F = K Q1Q2/r^2

Question 2

Define electric fields

Answer 2

It is a region of space in which an electric charge experiences a force.
The direction of the electric field at a point is the direction that a positive test charge would move if placed at that point

Question 3

Define the magnitude of the electric field at a point

Answer 3

It is the force per unit positive charge, E = F/q where E and F are vectors
The electric field at a point due to a point charge can be calculated using: E = kQ/r^2
Q must always be in coulombs and r must be in metres

Question 4

Electric field strength

Answer 4

This is the same as the magnitude of the electric field
It is a vector quantity and must be written with a direction
The unit is NC^-1