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# Announcements - PowerPoint PPT Presentation

Announcements. Homework for tomorrow… (Ch . 30, Probs. 29, 32, & 54) CQ6: I a = I d > I b = I c 30.14: 3.2 x 10 -3 A 30.17: a) 6.3 x 10 5 A/m 2 b) 6.6 x 10 -5 m/s Office hours… MW 12:30-1:30 pm TR 9-10 am F 10-11 am Tutorial Learning Center (TLC) hours:

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## PowerPoint Slideshow about 'Announcements' - roch

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Presentation Transcript

• Homework for tomorrow…

(Ch. 30, Probs. 29, 32, & 54)

CQ6: Ia= Id > Ib= Ic

30.14: 3.2 x 10-3 A

30.17: a) 6.3 x 105 A/m2 b) 6.6 x 10-5 m/s

• Office hours…

MW 12:30-1:30 pm

TR 9-10 am

F 10-11 am

• Tutorial Learning Center (TLC) hours:

M 8-1 pm, 3-6 pm, W 8-1 pm, 2-6 pm

TR 8-6 pm, F 8-2 pm

### Chapter 30

Current & Resistance

(Resistance and Ohm’s Law)

• Resistivity & conductivity…

• Ohm’s Law…

where

Notice: Ohm’s Law is NOT a Law!

The materials to which Ohm’s law applies are called Ohmic.

• i.e.’s: metals and conductors

Nonohmicmaterials:

• current, I, through the device is NOT directly proportional to the potential difference, ΔV.

• i.e.’s: diodes, batteries, and capacitors

The current through a wire is measured as the potential difference V is varied.

What is the wire’s resistance?

• 0.01 .

• 0.02 .

• 50 .

• 100 .

• Some other value.

Q: How does the voltage drop across the wires compare to the voltage drop across the resistor?

Q: How does the voltage drop across the wires compare to the voltage drop across the resistor?

A: ΔVwire << ΔVresist

i.e. 30.8:A battery and a resistor

What resistor would have a 15 mA current if connected across the terminals of a 9.0 V battery?