Week 1 Introduction and Electrostatic Field

Question 1

Define the Triboelectric Effect

Answer 1

Rubbing or touching between two objects can transfer electrons from one to the other

Question 2

Give four facts about charge

Answer 2

There are two types of charge
Charge is quantised in units of electron/proton charge
Charge is conserved
Charge is Lorentz invariant

Question 3

State Coulombs Law

Answer 3

F = Qq/4πεr^2

Question 4

What should you always look for in EM questions

Answer 4

Symmetry

Question 5

What is the simple Electric Field equation

Answer 5

E = F/q

Question 6

what are the four rules for the electrostatic field lines

Answer 6

Number of lines is arbitrary but density represents strength
Field lines either terminate at charge or extend to infinity
Field lines never cross
Direction of the force experienced depends on the direction of field lines

Question 7

what does Earnshaw’s Theorem state

Answer 7

Impossible to construct an electrostatic field that will hold a charged particle in empty space

Question 8

how do we find the charge distribution

Answer 8

integrate the charge density divided by r^2 over all points