PHY1004 Electricity and Magnetism

1999-2000

Code: PHY1004
Title: Electricity and Magnetism
Instructors: Dr H. Laidler
HE credits: 10
ECTS credits: 5
Availability: unrestricted
Level: 1
Prerequisites: none
Corequisites: none
Background Assumed: AS level Physics or equivalent
Duration: Semester II
Directed Study: 22 lectures
Private Study: 78 hours
Supports Programme Aims: 1 and 5
Supports Programme Objectives: none

Assessment Methods

Problems-class assignments (10%), two 30-minute tests (40%) and one 90-minute examination (50%).

Rationale

Electromagnetism is the study of electric charges, at rest and in motion. It is the second strongest of the four basic interactions of Physics and accounts for a wide range of the phenomena of everyday life. The theoretical treatment of electromagnetism and the use of appropriate mathematical techniques is progressively developed in the second year (PHY2206) and third year (PHY3120, PHY3126) electromagnetism modules.

This module surveys the phenomena associated with electrostatics (charges at rest) and magnetostatics (the magnetic effects associated with steady currents). It introduces and develops the use of the electric and magnetic field vectors and relates them by considering electromagnetic induction at a classical level. The connection between these fields and conventional circuit parameters R, C and L is developed, together with the techniques to deal with elementary transient phenomena.

Intended Learning Outcomes

Students should be able to:

• describe the vector nature of the electric field and its relation to a scalar potential; be able to calculate the force on a stationary charge due to other charges at rest and be able to relate this to the electrostatic energy of the system,
• state Gauss' law and appreciate its consistency with Coulomb's law; apply it usefully for charge distributions with high symmetry'
• describe the vector nature of a static magnetic field; be able to calculate the magnetic field, using the Biot-Savart law or Ampère's law as appropriate, for simple (but useful) circuits supporting steady currents and to be able to calculate the forces on such circuits when situated in a steady magnetic field,
• relate the electric and magnetic field vectors in circumstances where Faraday's law is valid, and solve related problems; give examples of the wide range of practical applications,
• relate the circuit parameters to the fields and the energy of those fields; know the features of transient response for circuit parameters in simple circuits.

Teaching and Learning Methods

Lectures, tutorials and problems classes

Transferable Skills

Ability to apply principles of electromagnetism to basic practical applications

Assignments

Two mid-semester tests and preparation for problems classes.

Module Text

Young H.D. and Freedman R.A. (1997), University Physics (9^th edition), Addison-Wesley, ISBN 0-201-31132-1-(ppbk) (UL: 530 YOU)

Supplementary Reading

Not applicable

Syllabus Plan and Content

1. Charge and Current
   1. Phenomena and practical applications of electrostatics
   2. Conservation and quantization of charge. Charge of an electron
   3. Units of current and charge
2. Coulomb's Law, Electric Field, Electrostatic Potential
   1. Coulomb's Law and the permittivity of free space.
   2. Electric field; vector nature of field, principle of superposition, field calculations for simple static charge distributions including dipole-field.
   3. Electrostatic potential; electrostatic potential energy of an assembly of charges, concept of potential and relation between electrostatic potential and electric field; the volt.
   4. Equipotential surfaces and field lines
3. Gauss' Law for Electrostatics
   1. Gauss' law and application to field calculations for simple geometry
   2. Fields and potentials for charged conductors. Electrostatic shielding
   3. Consistency with Coulomb's Law
4. Capacitance
   1. Determination of capacitance for simple electrode geometry
   2. Series and parallel connection of capacitors
   3. Introduction of dielectric; relative permittivity
   4. Energy stored in a capacitor and in unit volume in a uniform electric field
5. Steady Currents
   1. Current and current density
   2. Conductivity and resistivity; elementary model for a typical conductor
   3. Sources of EMF. Kirchhoff's rules. Dissipation of power in a resistor
6. Magnetic Effects of Steady Currents
   1. Elementary magnetic phenomena. Origin of static magnetic fields
   2. The Lorentz force law. The magnetic (induction) field B, the tesla. Measurement of B; the Hall-effect meter
   3. The Biot-Savart law. The permeability of free space. Calculations of B for simpler circuit geometry including the magnetic-dipole/current-loop.
   4. Ampère's law, demonstrated for magnetic field of a long straight wire carrying a steady current. Application to calculation of B for simple circuit geometry.
7. Forces on a Current in a Magnetic Field
   1. Force on current element
   2. Couple on a coil with simple geometry
   3. Force between parallel wires; definition of the ampère
8. Forces on Charges in Electric and Magnetic Fields
   Simple examples, e.g. cathode-ray oscilloscopes, television tubes, cyclotron, etc.
9. Electromagnetic Induction
   1. Phenomena and practical applications
   2. Faraday's and Lenz's laws
   3. Motional and transformer EMF's
   4. Self- and mutual inductance; the henry
   5. Calculation of self inductance of a long solenoid
   6. Stored energy
10. Transients
    Time constants; growth and decay of current and voltage in CR and LR circuits.

Feedback to Students

This module is supported by problems classes and tutorials. Students are able to monitor their own progress by attempting problems sheets provided in the lectures. The graded mid-semester test scripts are discussed by tutors. Students with specific problems should first approach their tutor, and if the problem is not resolved, the lecturer.

Feedback from Students

Feedback from students on the module is gathered via the standard student representation mechanisms.