ENGINEERING TRIPOS PART IA - 2012/2013

PAPER 3 - ELECTRICAL and INFORMATION ENGINEERING

Physical Principles of Electronics and Electromagnetics

Leader: Dr T.D. Wilkinson

Timing: Weeks 1-3, Michaelmas term & weeks 4-6 Lent term

Structure: 12 lectures, 2 lectures/week in two separate parts.

Part 1 - 6 Lectures: Physical principles of electronics

Part 2 - 6 Lectures: Electromagnectics

Please note: The new course is fundamentally the same as the course from previous years but with a different structure. The overall combination of Part 1 and 2 will be equivalent to the previous electromagnetics course and will be covered by section C in the final paper 3 examination.

AIMS

The aims of the course are to:

Develop an understanding of electromagnetic fields and their application to the solution of a range of engineering problems, building directly on the knowledge students have gained at A-level.

The emphasis during the course will be on the physical understanding of the principles involved. Only elementary mathematical methods will be used, including basic vector concepts of superposition, dot product and cross product.

The overall course will cover three mainareas through the two parts:(i) electrostatics: (ii) magnetic fields: and (iii) magnectic materials. Each part will contain a theoretical description of the concepts followed by applications to a range of problems of engineering interest.Part 1 is designed to introduce the physical properties of electromagnetics leading to the resistor, the capacitor and the inductor. This is done through a purley scalar theoretical analysis of the electromagnetic concepts. Part 2 takes the concepts of Part 1 and expands them on a more general sense to gain a more fundamental understanding of electromagnetic problem and materials. Throughout the course there will be an emphasis on the way approximation must be introduced when analysing engineering problems.

OBJECTIVES

As specific objectives, students should be able to:

• Understand the physical properties that lead to resistance, capacitance and inductance.
• Analyse simple geometries used in these components
• Understand the basic laws of electromagnetism.
• Calculate the electric and magnetic fields produced by simple charge and current distributions, using, where appropriate, analytical tools such as Gauss' law, Ampere's law, the method of images, and the finite difference method.
• Develop an understanding of the relation between field and circuit concepts.
• Calculate the capacitance, inductance, and mutual inductance for simple circuits.
• Understand how energy methods can be used to estimate electromagnetic forces.
• Design simple electromagnets and permanent magnets.

SYLLABUS (Book Page References)

Part 1 Physical principle of electronics (6 Lectures) (6L)

• Physical principles - charge and charge accumulation
• Coulomb's Law - from force to an empirical derivation of electric field (and and
• Charge flow - ohms law and current
• Simple derivation of current density (J)
• Simple description of resistance and resistivity
• The electric flux density (D) - simple geometries, point, line and surface
• Concept of electrical field (E) (with ref to point, line and surface)
• scalar definition of Gauss' law surface
• Electrostatic potential and voltage - scalar calculation EdI
• capacitance, Q=CV, examples:(i) parallel plate capacitor (ii) coaxial cable
• AC properties of capacitance (CdV/dt), simple definition of reactance (1/jwC)
• Empirical definition of force between current carrying wires
• Ideas of magnetic flux density (B) from between wires
• Simple Biot Savart Law to give a circulating magnetic field
• Examples: (i) B field around a wire, (ii) B field from a loop of wire, (ii) field in a solenoid
• Scalar version of Ampere's law based on flux density circulating a wire
• Concept of Magnetic flux and flux linkage
• Faraday's Law of a electromagntic induction
• Inductance, examples of coil and coaxial line, definition of mutal inductance
• AC propertise of inductance (jwl)

Part 2- Electrmagnetics (3L)

Electrostatic systems (3 lectures)

• Dielectrics, idea of polarisation charges, dielectric breakdown
• Vector definition of E-feld and Gauss' Law
• Gauss' Law with dielectric boundaries and conservation at a boundary
• Energy in a capacitor and electric field. Energy storage + effect of dielectrics
• Using virtual work to estimate forces (const voltage version) + examples

Magnetic systems and materials (3 Lectures)

• Need for magnetic materials
• Ideas of magnetic field (H) and the relative permeability
• Ampere's Law with linear, MMF, Vector form of Ampere's Law.
• Non-linear materials, saturation, magnetistion curve and hysteresis, tranformers?.
• Permanent magnets.
• Energy and forces in magnetics circuits - virtual work example.
• Magnectis energy as integral of HdB
• Estimating forces between magnetics materials (EM and permanent)

REFERENCES:

Please see the Booklist for Part IA Courses for module references

Last updated:May 2012