{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

ASSIGN3

# ASSIGN3 - Section Name Section Instructor Assignment 3...

This preview shows pages 1–2. Sign up to view the full content.

Section: ______ Name: ______________________________ Section Instructor: ______________________________ Assignment 3: Charges in Motion & Electric Circuits Concepts: electric current current density charge carriers and drift speed resistance and resistivity Ohm’s law energy and power in electric circuits “pumping” charges and emf calculating and measuring voltage and current simple multiloop circuits (series, parallel) RC circuits Reading in text: Chapter 26: Sections 1-5, 7. Chapter 27: Sections 1-9. Assignment: Due in lecture on Friday February 13. Quiz may be given on Thursday February 12 or Friday February 13. 1. In the lower atmosphere of the Earth there are negative and positive ions, created by radioactive elements in the soil and cosmic rays from space. The density of singly charged negative ions is 550 , while the density of singly charged positive ions is 620 . In a certain region, the strength of the fair weather atmospheric electric field is 120 V/m, directed vertically downward, and the measured conductivity is 2 7 3 / cm 3 / cm 10 14 . / ( ) × Ω m . (a) What is the direction of drift of each kind of ion? (b) What is the direction of the total electric current? Do the motions of the two kinds of ions produce electric currents that add or subtract? Please explain. (c) What is the electric current density ? (d) What is the ion drift speed , assuming it to be the same for both kinds of ions? (e) If this current density were the same over the entire surface of the Earth, what would be the total electric current carried by these atmospheric ions? (f) Does the charge transfer due to this current tend to enhance or diminish the atmospheric electric field? Please explain. 2. A common flashlight bulb is rated at 0.30 amp and 3.0 volts (the values of the current and voltage under operating conditions). (a) What is the bulb’s resistance when lit? (b) What electric power is dissipated into light and thermal energy by the bulb?

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

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}