EM Fall2015

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

Contents 1 Schedule for Tutoring Sessions -- Fall 2015 2 Pre-mid term 3 Mid-term 4 Post-mid term

Electricity and Magnetism

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 Assistant	Time	Day	Venue
[Saba Asif Baig]	2:30 to 3:30 pm	Monday	Physics conference room.
[Aman Fatima]	10-11 am	Friday	Physics conference room
[Waleed Khalid]	2-3 pm	Tuesday	Physics conference room
[Abdullah Bin Faisal]	3:30-4:30 pm	Wednesday	Physics conference room
[Osama Naeem]	10-11 am	Thursday	Physics conference room
[Lala Rukh]	4-5 pm	Thursday	Physics conference room
[Marium Rasheed]	11 am-1 pm	Friday	Physics conference room

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Pre-mid term

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

Electric Fields (2 lectures)

• 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]

• Recitation on electric fields 4 September 2015. Solution.

• Tutorial on electric fields Week of 7 September 2015

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]

• Recitation on Gauss's law 11 September 2015. Solution.

• Tutorial on Gauss's law Week of 14 September 2015

• 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.

• Quiz 1 dealing with Gauss's law and its 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]

• Recitation on electric potential 2 October 2015. Solution.

• Tutorial on electric potential Week of 28 September 2015.

• Homework 2. Due date is Wednesday, 7 October 5 pm. Solution.

• Quiz 2 deals with electric fields, electrostatic energies and potential. Solution.

Currents, batteries, semiconductors (5 lectures)

• Electric current, here exists an electric field inside a conductor, current density and its relation to carrier density, Drude's model, "deriving" Ohm's law [9]; Demonstrations: Heating by cooling: lighting a bulb by dipping the circuit inside liquid nitrogen.

• 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]

• Tutorial on electric current. Week of 5 October 2015. Students will continue with this tutorial in the week of 12 October 2015.

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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.

• Applications of Ampere's law: field due to solenoid, toroid, current carrying loop, magnetic dipoles, Lorentz forces, forces between conductors [14]. Demonstrations: Forces between current carrying conductors.

• 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].

• Tutorial on sources of magnetic fields Week of 26 October 2015. Continue with this tutorial in the week of 2nd November.

• Homework 3. Due date is Thursday, 29 October 5 pm. Solution.

• Recitation on forces and torques inside magnetic fields. 5 November 2015. Solution.

• Tutorial on forces and torques inside magnetic fields Week of 9 November 2015.

• Homework 4. Due date is Thursday, 12 November 5 pm. This homework must be solved individually. Solution.

• Quiz 3 deals with magnetic field patterns, Ampere's and Gauss's law for magnetism.

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.

• Ferromagnets, hysteresis loop, magnetic domains, diamagnets, superconductors and the Meissner effect [18]. Demonstrations: Levitation due to the Meissner effect.

• Tutorial on magnetic materials. Week of 16 November 2015. Solution.

Varying electric and magnetic fields and fluxes (5 lectures)

• Faraday's law modified under varying magnetic fluxes, eddy currents, Lenz's law [19]. Demonstrations: Electromagnetic induction and eddy currents and Lenz's law.

• 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].

• Homework 5. Due date is Wednesday, 25 November 5 pm. Solution.

• Tutorial on changing magnetic and electric fluxes. Week of 23 November 2015.

• Recitation on electromagnetic induction. 26 November 2015. Solution.

• Tutorial on energy flow in electric circuits. Week of 30 November 2015.

• Quiz 4 largely deals with electromagnetic induction.

Some circuit elements (4.5 lectures)

• Capacitors, capacitance, charging and discharging (field description), capacitance of select geometries, energy inside electric and magnetic fields [24].

• Behavior of capacitors and inductors compared, inductance, self inductance and mutual inductance, path dependence of electric fields [25]. Demonstrations: and discharging of a capacitor and mutual induction and path dependent electric fields.

• 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].

• Recitation on capacitance. 4 December 2015. Solution.

• Homework 6. Due date is Monday, 14 December 5 pm. This is an individual homework and will be coarsely graded. Solution.

• Quiz 5 solution.

Electromagnetic waves (2 lectures)

• 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].

• Here is a clean derivation of the radiation formula stated inside the classroom. It is Appendix H of the Purcell and Morin's book on "Electricity and Magnetism".

• Click here to download diagrams of field configurations from moving charges again taken from Purcell and Morin's book on "Electricity and Magnetism".

• Read Ch. 34 and attempt selected problems of Jewett and Serway's "Physics for Scientists and Engineers".