Mon 14 ELT2
Tue 11 BLT1
Fri 11 ELT2 NOT WEEK 1
The entire course comes in 3 chunks with 2 class tests and 6 assignments distributed uniformly:
Electrostatics
Electromagnetism
Optics
Prof Michael Smith will deliver the first 10 lectures and a class test.
Lecture notes for electrostatics will be posted on: http://astro.kent.ac.uk/mds/Modules/modules.htm
Previous yea rs’ notes and assignments are also available.
Completed assignments must be handed to me directly after a Lecture. This is the only method accepted. Deadlines are strict.
Experiments on electrostatics will not be undertaken. Therefore, you might wish t o watch Walter Lewin’s lectures on video (not a requirement). You can download and save from: http://ocw.mit.edu/courses/physics/8-02-electricity-and-magnetism-spring-
2002/video-lectures/ http://ocw.mit.edu/ans7870/8/8.02/videolectures/wl-802-lec1-220k.rm
Also online on youtube, and at http://ocw.mit.edu/OcwWeb/Physics/8-02Electricity-and-
MagnetismSpring2002/CourseHome/
Assignments:
MDS
1 Intro Math
1 Electrostatics
MDS Topics:
1

1.
Complex numbers, partial differentiation
2.
Vectors
3.
Review of PH301 section on EM
4.
Coulomb’s law, Gauss’ law
5.
Potential energy and electric potential
6.
Electric dipole
7.
Gauss law
8.
Capacitance
9.
Dielectrics; polarisation
10.
Boundary conditions for E, D
11.
Method of Images
PH301: topics covered
Electric current. Resistivity, resistance. Electromotive force and circuits.
Energy and power in electric circuits.
Theory of metallic conduction. Resistors in series and in parallel.
Kirchhoff.s rules. Electrical measuring instruments. RC, RL, LC and LRC circuits. Phasors and alternating currents. Reactance. LRC series circuits. Series and parallel resonance Potential dividers ,Thevenin.s theorem, Maximum power transfer, Potentiometer, Bridge circuits, The transformer.
1. Strength: Even though electrostatically induced forces seem to be rather weak, the electrostatic force between e.g. an electron and a proton , that together make up a hydrogen atom , is about 40 orders of magnitude stronger than the gravitational force acting between them.
2. Annoyance.
Static charge, bad hair days, wrinkled clothes, dog hair that I can’t get off of my pants.
3. Application
2

Ink Jet Printer – words written by deflection of ink droplets in electrostatic fields
Ion Mass Spectrometers . Why do they swab your bags at the airport?
The compounds acquired are desorbed and ionized. The ions are accelerated toward the detector by a constant electric field gradient in the drift region.
Since the ‘flight’ depends on ion mass and charge, explosives can be detected.
3

There are two types of charges: positive and negative.
Like charges repel and opposite charges attract.
Coulomb’s law:
F = Q
1
Q
2
/(4 
0 r 2 ) where 
0
is the permittivity of free space.
A conductor allows electric charge to travel through it easily.
An insulator does not.
Charges can flow through a metal with very little resistance.
Rubber, for instance, has its atoms arranged such that it is very difficult for electric charge to flow through it. Rubber is considered to be an insulator.
All materials have a certain conductivity. The conductivity of a material depends on the materials arrangement of free electrons.
Below is a chart of some common materials and their conductivities.
Electrical Conductivity
(1/(ohm*m)) Material
Silver
Copper
Lead
Wood
Glass
Hard Rubber
60 x 10
60 x 10
5 x 10
10
6
6
6
-8 - 10 -14
10 -10 - 10 -14
10 -13 - 10 -16
Values taken from Tipler, Paul A. Physics, Third Edition. 1991.
4

A person's body acts as a conductor.
The skin has a very large resistance (on the order of MegaOhms).
The salt water (electrolyte) solution that is in your body is designed specifically to conduct electricity, so that your nerve impulses can reach the muscles.
Triboelectric Series. When certain types of materials are rubbed against other certain types, charge may be transferred from one to the other. The amount and type of charge is determined by the
Triboelectric Series. The Triboelectric Series is a list of materials which determines which materials will become positively charged and which will become negatively charged when rubbed together.
A sample portion of the Series is shown below.
To read the chart, those materials nearer the top will become positively charged and those nearer the bottom will become negatively charged. For instance, when Teflon is rubbed against silk, the Teflon becomes negatively charged and the silk becomes positively charged.
Aircraft & Space launch Vehicles can become charged.
Polarisation. When an uncharged object is placed near a charged object its charges rearrange themselves. Those charges attracted to the charged object move towards the charged object and those charges repelled move away. This effect is known as polarization.
5

Charges on a conductor tend to gather at sharp points.
A metal cone, for instance, which has been charged will have a lot of charge at the point, and much less charge elsewhere.
WHY ??
6