HW29 - Thevalingam, Donald – Homework 28 – Due: May 31...

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

View Full Document Right Arrow Icon

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

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

Unformatted text preview: Thevalingam, Donald – Homework 28 – Due: May 31 2007, midnight – Inst: Eslami 1 This print-out should have 34 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. 001 (part 1 of 1) 10 points The current in a wire decreases with time according to the relationship I = (2 . 61 mA) × e- a t where a = 0 . 13328 s- 1 . Determine the total charge that passes through the wire from t = 0 to the time the current has diminished to zero. Answer in units of C. 002 (part 1 of 1) 10 points A copper wire carries 1 amp of electric cur- rent. What kind of charge does the electron flow create in the wire? 1. No charge. 2. Negative 3. Positive 003 (part 1 of 1) 10 points In a fluorescent tube of diameter 4 . 4 cm, 1 . 1 × 10 18 1 / s electrons and 1 × 10 17 1 / s positive ions (with a charge of + e ) flow through a cross-sectional each second. What is the current in the tube? Answer in units of A. 004 (part 1 of 5) 10 points A current of 25 A exists in a copper (Cu) wire which has a diameter of 1 mm. Each atom of copper has one conduction band, and the average thermal speed r k T m of an electron is 100000 m / s . The mass den- sity of Cu is 8 . 92 g / cm 3 , its molar mass is 63 . 5 g / mol, and Avogadro’s number is 6 . 02214 × 10 23 atoms / mole. The electron mass is 9 . 10939 × 10- 31 kg, and the resistivity of copper is 1 . 7 × 10- 8 Ω · m. What is the current density? Answer in units of A / m 2 . 005 (part 2 of 5) 10 points What is the density of conduction electrons band of copper? Answer in units of m- 3 . 006 (part 3 of 5) 10 points What is the drift velocity of the electrons? Answer in units of m / s. 007 (part 4 of 5) 10 points What is the average time between collisions of the “drifting” electrons with the lattice ions? Answer in units of s. 008 (part 5 of 5) 10 points What is their mean free path in this wire? Answer in units of m. 009 (part 1 of 2) 10 points The quantity of charge passing through a sur- face of area 1 . 02 cm 2 varies with time as q = q 1 t 3 + q 2 t + q 3 , where q 1 = 5 . 5 C / s 3 , q 2 = 4 . 4 C / s, q 3 = 8 C, and t is in seconds. What is the instantaneous current through the surface at t = 0 . 9 s? Answer in units of A. 010 (part 2 of 2) 10 points What is the value of the current density at t = 0 . 9 s? Answer in units of A / m 2 ....
View Full Document

This note was uploaded on 04/05/2010 for the course PHY 52033 taught by Professor Tleva during the Spring '10 term at University of Texas.

Page1 / 7

HW29 - Thevalingam, Donald – Homework 28 – Due: May 31...

This preview shows document pages 1 - 2. Sign up to view the full document.

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