Lecture 28  iq24

1. Magnetic force on a current segment. Ch21 h1 006

o Force on || wires (same direction lead to attraction, opposite leads to repulsion)

2. Current loop in presence of const B.

o Net force vanishes.

o Torque on a loop, when B is in the plane of the loop. Ch21. h1.010-012

o General case: Ch21: h1, 013-015

3. Circular motion in the plane perpendicular to a constant B field. Ch21-h2-03.

o Period independent of r and v.

o Cyclotron

o Bending electrons in the magnetic field

4. Hall effect: h2: 006-010

o Experiment which determines the sign of the carrier charge.

o Direction of Hall current

o Calculate the Hall voltage

o Relationship between number density and the mass density.

o One mole has

§ the molar mass M, and

§ has #-free electrons=(# valence electrons)N_A.

Announcement:

Learning module:

Feedback will be incorporated into the lecture.

The learning modules will count as part of the homework score: instead of homework accounting for 15%, we now have homework at 12% and leaning modules at 3%.

Feedback on homework: This feedback will be used as the baic content for discussion sessions. In order to encourage participation, we have made HW feedback part of the iq clicker credit:

o iq clicker now counts for 5%,

o while feedback counts for 2%.

The latter is an easy 2%, as all you need to do is tell us which problem you found most confusing on a particular assignment and why. The feedback will be due on the same evening the homework is due, but the due time will be 11:50 to give those last-minute types a chance to enter feedback after completing the homework.

Words from Josh: “Please note that I will be reading the feedback, so if you enter something like "no comment" or a random string of keystrokes, you will not receive credit. Please make a sincere effort to give quality feedback, as it will have a direct effect upon the quality of your instruction.”