From Physlab.lums.edu.pk

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

## Contents |

**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.

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 |

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.

**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.

**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.

**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.

**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.

**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.

**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".