This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: lew (dl9564) hw 6 Opyrchal (121006) 1 This printout should have 13 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 points A conductor with crosssectional area 4 cm 2 carries a current of 19 A. If the concentration of free electrons in the conductor is 5 10 28 electrons / m 3 , what is the drift velocity of the electrons? Correct answer: 0 . 00592943 mm / s. Explanation: Let : I = 19 A , n = 5 10 28 electrons / m 3 , q e = 1 . 60218 10 19 C , and A = 4 cm 2 = 0 . 0004 m 2 . The current in a conductor is given by I = n q v d A , where n is the number of charge carriers per unit volume, q is the charge per carrier, v d is the drift velocity of the carriers and A is the cross section of the conduction. Solving for v d , we have v d = I n q A = 19 A 5 10 28 electrons / m 3 1 1 . 60218 10 19 C 1 . 0004 m 2 1000 mm 1 m = . 00592943 mm / s . 002 10.0 points A wire with a resistance R is lengthened to 6 . 62 times its original length by pulling it through a small hole. Find the resistance of the wire after it is stretched. Correct answer: 43 . 8244 R . Explanation: Let : = 6 . 62 . The volume V of the wire is given by V = A, where is the length of the wire and A is the crosssectional area. When the wire is stretched to a length , the volume will re main the same. The new crosssectional area is then, A = A A = A = A 6 . 62...
View
Full
Document
This note was uploaded on 03/22/2009 for the course PHYS 121 taught by Professor Opyrchal during the Fall '08 term at NJIT.
 Fall '08
 Opyrchal

Click to edit the document details