Midterm1Solution

Midterm1Solution - PHYSICS 9C MIDTERM 1 February 3 , 2011 I...

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PHYSICS 9C MIDTERM 1 February 3 , 2011 I certify by my signature below that I will abide by the UC Davis Code of Academic Conduct. This includes not copying from anyone else’s exam not letting any other student copy from my exam not discussing this exam with any student who has not yet taken it, nor providing any information, written or oral, that might get to a student who has not yet taken it. Anyone suspected of cheating will be automatically reported to Student Judicial Affairs. LAST NAME: FIRST NAME: STUDENT ID: (P R I N T) (P R I N T) (LAST 4 DIGITS) Signature: Problem 1 (two points) . Three very large parallel uniformly charged non-conducting sheets with the surface density =+8.85x10 -12 C/m 2 are placed at the distance L=5cm one from each other. What is the value of electric field between the sheets, outside the sheets? A) 0 N/C between all sheets, 1.5 N/C outside. B) 1.5 N/C between all sheets, 0 N/C outside. C) 1.5 N/C before first sheet, 1 N/C between first and second sheet, 0.5 N/C between second and third sheet, 0 N/C beyond third sheet. D) 1.5 N/C before first sheet, 0.5 N/C between first and second sheet, 0.5 N/C between second and third sheet, 1.5 N/C beyond third sheet. E) 0 N/C before first sheet, 0.5 N/C between first and second sheet, 1 N/C between second and third sheet, 1.5 N/C beyond third sheet. Solution: Each sheet produces electric field directed to the left from its left, and directed to the right from its right. The value of the electric field from each sheet is σ /2 ε 0 =0.5 N/C. From the very left and very right, all three sheets contribute to the field, therefore E=3*0.5=1.5 N/C. In the region between sheet 1 and 2 as well as between 2 and 3 contributions from 2 sheets cancel, therefore E= 0.5 N/C. Answer D Ε? Ε? Ε? Ε? 1 2 3
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A B C D E V(x) Problem 2. (two points) The figure shows the dependence of electric potential as a function of coordinate. In which region the value of the electric field is greatest? Solution. Since the electric field is given by the derivative of the potential with respect to coordinate, () dV Ex dx =− it is the region B where the derivative is largest.
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This note was uploaded on 11/11/2011 for the course PHY 9C taught by Professor Zieve during the Spring '08 term at UC Davis.

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Midterm1Solution - PHYSICS 9C MIDTERM 1 February 3 , 2011 I...

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