EM Fall2015

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You can see the previous offering of this course from Fall 2014 here.

Contents


Electricity and Magnetism

Image:em2015.jpg

Instructor: Dr. [Sabieh Anwar]. Office hours are Tuesday 10 am to 12 pm. Recitations will be led by Mr. [Nauman Ahmad Zaffar].

Teaching Instructors: See the schedule for tutoring sessions below.

Course outline: Click here for the course outline.

Schedule for Tutoring Sessions -- Fall 2015

Teaching AssistantTimeDayVenue
[Saba Asif Baig] 2:30 to 3:30 pmMondayPhysics conference room.
[Aman Fatima] 10-11 amFridayPhysics conference room
[Waleed Khalid] 2-3 pmTuesdayPhysics conference room
[Abdullah Bin Faisal] 3:30-4:30 pmWednesdayPhysics conference room
[Osama Naeem] 10-11 amThursdayPhysics conference room
[Lala Rukh] 4-5 pmThursdayPhysics conference room
[Marium Rasheed] 11 am-1 pmFridayPhysics conference room

Pre-mid term

To access the video recordings, click on the numbered links below.

Electric Fields (2 lectures)

Click here to see the Wimshurst machine. in action.
Click here to see the Wimshurst machine. in action.
  • Electric charge, Coulomb's law, vector fields, electric field, superposing electric fields [1]
  • Electric field due to distributed charges, electric dipoles, connection between electrostatic and mechanics problems, field due to a charged rod, charge disk [2]

Gauss's law (3 lectures)

  • Electric flux, flux through a closed sphere concentric with a point charge, flux through arbitrary shaped surfaces and charge distributions [3]
  • Formal statement of Gauss's law, using Gauss's law to determine electric fields (line, sheet of charge), role of symmetry, fields inside conductors; Demonstrations: Wimshurst machine and Gauss's law [4]
  • Spherical symmetry, fields around and inside conductors, a charged metal ring enclosing an insulating sphere [5]
  • Homework 1. This is a collaborative assignment. Work in groups of up to three. Due date is Wednesday,16 September 5 pm. Drop homework solutions inside the orange boxes in the Physics corridor. Solution.

Electric potential (3 lectures)

  • Electric potential energy defined using first law of thermodynamics (energy conservation), potential energy of a system of charges, potential energy o a charge inside the field of a point charge [6]; Demonstrations: Ionic wind and corona discharge.
  • Relation between electric field and electric potential, relation between electric potential and potential energy, potential due to a sphericaly symmetric distribution of charges, potential between parallel plates, a metal is an isopotential surface. [7]
  • Electric potential due to series of parallel plates, coaxial conductor, dependence of potential on size, path independence of potential, line integral of electric field around closed paths [8]

Currents, batteries, semiconductors (5 lectures)

  • Negative electric feedback explaining consistency of current through bent wires, dissimilar metals, graded conductors, motivating Kirchoff's current law [10].
  • Surface charges enabling the flow of current in surface conductors, introduction to batteries Part A and Part B. There was an error in my description towards the end. The slope of the potential inside the battery is E/s instead of E and the potential rise is E instead of Es. Demonstrations: The resistance of a semiconductor drops with temperature.
  • Classes of materials based upon conductivity, intrinsic and extrinsic semiconductors, band diagrams, PN junction and depletion layer [11].
  • A holistic view of how a PN junction works, recombination and thermally assisted charge carrier generation, biasing a diode, field and potential landscape [12]

Mid-term

Midterm and its solution.

Post-mid term

Producing magnetic fields and moving charges inside magnetic fields (4 lectures)

  • Moving charges produce magnetic fields, Oersted's discovery, Biot-Savart law, field due to an infinitely long wire, Ampere's law [13]. Demonstrations: Oersted's discovery.
  • Charges move in circular orbits inside magnetic fields, combined magnetic and electric fields, example of the cyclotron, forces and torques on magnetic dipoles, energy of a magnetic dipole inside a magnetic field [15] . Demonstrations: Steering electron paths using magnetic fields inside a cathode ray tube.
  • Forces between dipoles, fields due to sheets of current, reviewing in total electric and magnetic fields inside and around current carrying conductors [16].
  • Homework 4. Due date is Thursday, 12 November 5 pm. This homework must be solved individually. Solution.

Magnetism inside matter (2 lectures)

  • Atomic origins of magnetism, spin, Stern-Gerlach experiment, phenomenological classification of magnetic materials, relations between B, H and M, magnetic susceptibility [17]. Demonstrations: Forces on conductors inside magnetic fields.

Varying electric and magnetic fields and fluxes (5 lectures)

  • Magnetic braking, domain wall pinning and Barkhausen effect, what is meant by a non-conservative field, induced emf, example of a wire close to another wire carrying a time-varying current [20]. Demonstrations: Magnetic braking.
  • Moving magnets near a coil, solenoid carrying varying current placed near a pickup coil, uniform and non-uniform cross section pickup coils, superconducting coils and Meissner effect, skin effect, why diamagnetism, generator coil, shrinking ring in a uniform field [21].
  • Motional emf, falling conductor inside a magnetic field, where is the power coming from, uniform magnetic fields cannot do work, Hall effect, origin of forces acting on current carrying conductors [22].
  • Some nuances about the motional emf, fields and currents inside superconductors,homopolar generator, Maxwell-Ampere's law [23].

Some circuit elements (4.5 lectures)

  • Capacitors, capacitance, charging and discharging (field description), capacitance of select geometries, energy inside electric and magnetic fields [24].
  • Energy flow in a simple circuit, Poynting vector, "deriving" Ohm's law [26].
  • Using Poynting vectors to describe energy inflow into a capacitor, two alternative ways of finding out the energy inside a capacitor, fields harbor energy, energy inside an inductor, what happens when a metal is placed inside a capacitor, polarizability of molecules [27].
  • Homework 6. Due date is Monday, 14 December 5 pm. This is an individual homework and will be coarsely graded. Solution.

Electromagnetic waves (2 lectures)

Image:moving-charges.jpg

  • Dielectrics inside capacitors, relative permittivity, a possible field configuration for electromagnetic waves, speed of light [28].
  • How are electromagnetic waves produced, accelerating charges, concept of radiation, EM waves transfering energy and momentum, Poynting vector seen again [29].
  • Read Ch. 34 and attempt selected problems of Jewett and Serway's "Physics for Scientists and Engineers".
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