1 / 19

Announcements

Announcements. Homework for tomorrow… (Ch . 30, CQ 11, Probs. 18, 20, 38) 30.3: 2.1 x 10 24 30.6: a) 4.6 x 10 21 b) 4.4 x 10 -12 m 30.7: 1.0 x 10 19 s -1 Office hours… MW 12:30-1:30 pm TR 9-10 am F 10-11 am Tutorial Learning Center (TLC) hours:

Download Presentation

Announcements

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Announcements • Homework for tomorrow… (Ch. 30, CQ 11, Probs. 18, 20, 38) 30.3: 2.1 x 1024 30.6: a) 4.6 x 1021 b) 4.4 x 10-12 m 30.7: 1.0 x 1019 s-1 • 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

  2. Chapter 30 Current & Resistance (Conductivity and Resistivity & Resistance and Ohm’s Law)

  3. Review… • Current.. • Current Density.. • Kirchoff’s Junction Rule.. • Current Density related to the E-field..

  4. Quiz Question 1 The current density in this wire is • 4  106 A/m2. • 2  106 A/m2. • 4  103 A/m2. • 2  103 A/m2. • Some other value.

  5. 30.4:Conductivity and Resistivity How the current density, J, is related to the E-field driving the current: where SI Units?

  6. 30.4:Conductivity and Resistivity How the current density, J, is related to the E-field driving the current: Where SI Units?

  7. Quiz Question 2 Both segments of the wire are made of the same metal. Current I1 flows into segment 1 from the left. How does current I1 in segment 1 compare to current I2 in segment 2? • I1> I2. • I1 = I2. • I1 < I2. • There’s not enough information to compare them.

  8. Quiz Question 3 Both segments of the wire are made of the same metal. Current I1 flows into segment 1 from the left. How does current density J1 in segment 1 compare to current density J2 in segment 2? • J1J2. • J1J2. • J1J2. • There’s not enough information to compare them.

  9. Quiz Question 4 Both segments of the wire are made of the same metal. Current I1 flows into segment 1 from the left. How does the electric field E1 in segment 1 compare to the electric field E2 in segment 2? • E1 > E2. • E1 = E2 but not zero. • E1 < E2. • Both are zero because metal is a conductor. • There’s not enough information to compare them.

  10. 30.4:Conductivity and Resistivity Define the resistivity… SI Units?

  11. 30.4:Conductivity and Resistivity Define the resistivity… SI Units?

  12. 30.4:Conductivity and Resistivity Define the resistivity… SI Units?

  13. i.e. 30.6:The E-field in a wire A 2.0 mm diameter aluminum wire carries a current of 800 mA. What is the E-field strength inside the wire?

  14. 30.5:Resistance and Ohm’s Law How is the current, I, related to the potential difference, ΔV in a wire?

  15. 30.5:Resistance and Ohm’s Law How is the current, I, related to the potential difference, ΔV in a wire? SI Units of R? - Ohm’s Law

  16. 30.5:Resistance and Ohm’s Law How is the current, I, related to the potential difference, ΔV in a wire? SI Units of R? - Ohm’s Law

  17. 30.5:Resistance and Ohm’s Law Notice: • Resistivity, ρ, describes just the material. • Resistance, R, characterizes a specific piece of the conductor with a specific geometry. Resistance of a wire

  18. Quiz Question 5 Wire 2 has twice the length and twice the diameter of wire 1. What is the ratio R2/R1 of their resistances? • 1/4. • 1/2. • 1. • 2. • 4.

  19. Resistance and Ohm’s Law • A battery is a source of potential difference Vbat. • The battery creates a potential difference Vwire= Vbatbetween the ends of the wire. • The potential difference in the wire Vwire generates an E-field in the wire. • The E-field establishes a current I = JA = σAE in the wire. • The current in the wire is determined jointly by the battery and the wire’s resistance, R to be: • IVwire/R

More Related