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Physics 2212C Summer 2007 Test form Quiz 2211 Name ___________________________
Instructions: 1) Select a seat with a RED stenciled letter matching the seat assignment at right. seat:
2) Print your name, test form number (above) , and nine-digit student number in thesection of the answer card labeled "STUDENT IDENTIFICATION". A
- Bubble your test form number in columns 1-3, skip column columns 5-13. 4, then bubble in your student number in
- For each multiple-choice question, select the answer most test , and bubble it in on your answer card. Show all relevant work on your quiz. nearly correct, circle this answer Do not put on (^) your extra marks on the card.
- Turn when init (^) hasyour been test graded.and answer Quiz card grades and (^) leave. become Your final score when will the be next posted quiz (^) under is given. "Course Standing"
- You may use a calculator that cannot store letters, but no other aids. k = 8.99 x 10^9 N·m^2 /C^2
εo = 8.85 x 10 –12^ C^2 /N·m^2
e = 1.60 x 10–19^ C m e = 9.11 x 10 –31^ kg Blank work. space If you — have Feel any free hand-graded to use this (^) work space here, for scratch please label relevant page. it clearly, and make a note of this fact on the^ Standard^ Integrals:
The following problem will be hand-graded. Show all your work for this problem. Make no marks and^211 leave no space on your answer card for it. [I] Discussion within a conductor. & Analysis: Necessarily, Electric thiscurrent implies is a non-equilibriumthe existence of aprocess non-zero involving internal moving field within charges the material of the conductor. (a) (9 distribution of charge points) Explain qualitatively (if any) would what you causes expect the to internal find in/on field a current-carryingto come into existence. wire? Sketch What in this distribution of the wire segment below. Indicate clearly the particle current ( i ), and the charge current ( I ) within the wire. the directions of the internal field ( E ),
(b) (6 approximate acceleration would this give to an electron? points ) In a typical situation, the internal field strengthHow can is youof thereconcile order your 10 – 2 resultN/C. withWhat the known fact that typical drift speeds are very slow?
The following problem will be hand-graded. Show all your work for this problem. Make no marks and^211 leave no space on your answer card for it. [III] A silver wire of unspecified of radiusradius, R (^) asis splicedshown toat a (^) right.copper wireThe number density is given by: of mobile electrons in each material n (Ag) = 5.8 x 101 9^ e – /mm^3 n (Cu) = 8.5 x 10 1 9^ e – /mm^3
R Ag Cu I
(a) (9 junction (in the copper) at points) What radius should half the speed that they arrive at the copper wire be, in order the junctionfor electrons (in the to silver). drift away Express from your the answer in terms of the radius R of the silver wire.
(b) (6 silver wire? Express your answer as ratio: points ) How does the current density in the copper wire compare to the current density in the
The following problem will be hand-graded. Show all your work for this problem. Make no marks and^211 leave no space on your answer card for it. [IV] A sheath very (^) thatlong, extends conducting from radiuscylinder R (^) tohas radius a radius 2 R. R This. The sheath conductor carries is asurrounded uniform charge by an densityinsulating ρo throughout its volume. It is found that the field everywhere outside the sheath is identically zero. ηο^ ρο
(a) (9 points) and use that information (along with Compute an expression for the Gauss’s total Law) charge found on a length to infer the surface chargeΔ L of the density insulating ηo that sheath, must exist on the conductor. Express your answer in terms of ρo R , and any other necessary constants.
(b) (6 points Express your answer in terms of) Use Gauss’s Law to find an expression for the electric field ρo R , r , and εo. E(r) in the region R ≤ r ≤ 2 R.
(4)^ Question value 10 points A disk of diameter D = 9.0 cm is oriented in a uniform field as shown. If the field magnitude is the electric flux through the disk? is 1500 N/C, what (a) 9.5 N·m^2 /C (b) 4.8 N·m^2 /C (c) 8.3 N·m^2 /C (d) 6.1 N·m^2 /C (e) 11 N·m^2 /C
D^30 °^ E
(5)^ Question value 10 points The three represent current-carrying wires, each made of a different material. The diameter, current, and three wires. internal field for each wire is indicated. Rank, from greatest to least, the conductivities of the
E
I
D 1 / 2 E
2 / 3 I
D 1 /^2 E
1 / 2 I
1 / 2 D
Wire A Wire B Wire C (a) σ A > σ B > σ C (b) σ C > σ B > σ A (c) σ B > ( σ C = σ A ) (d) σ B > σ A > σ C (e) ( σ C = σ A ) > σ B
