p240_ct11_w12_feb_9 - Physics 240 Winter 2012 Lecture #11...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
Physics 240 Winter 2012 Lecture #11 Dr. Dave Winn 2405 Randall winn@umich.edu My Office Hours (1416 Randall Lab) Monday 1pm-3pm Tuesday 1pm-3pm Thursday 2pm-4pm (Prof. Gidley) Learning Assistant Office Hours Tuesday 4-8pm Thursday 4-6pm Also in chat room Tue/Thu evening!
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
In the circuit shown, the two bulbs A and B are identical. Compared to bulb A , A. bulb B glows more brightly. B. bulb B glows less brightly. C. bulb B glows just as brightly. D. answer depends on whether the mobile charges in the wires are positively or negatively charged Q25.6
Background image of page 2
Electrical resistance For many materials V = IR Units of resistance = Vs/C = Ohms (sym: ) Where the resistance R depends on resistivity and geometry, for example R = (L/A) Power dissipated in resistors P=I 2 R=V 2 /R Current Voltage I = (1/R)*V Symbol for resistors:
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Other materials… Ohm’s law is not a good approximation for the conductivity of some materials. For these the relation between I and V can be more complex Semiconductor diodes are an example An example: a “diode”, or one way current device. Demo: negative temperature coefficient
Background image of page 4
To maintain a current in a circuit, something must ‘pump’ positive charge from low to high potential This ‘electromotive force generator’, EMF device, must do work on charges to make this happen Some examples:
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 20

p240_ct11_w12_feb_9 - Physics 240 Winter 2012 Lecture #11...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online