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Unformatted text preview: PHYS 0175 (Spring 2008) — Worksheet Problem #4 (Part A)
Your Name: K 0 E H L E TA: Score: The smiling face shown in the figure below consists of four charge-carrying elements: (a) a thin non-
conducting rod bent into a full circle of radius r1=0.900 m with a net charge q1=+25.0 nC spread uniformly
over its length; (b) a thin non-conducting rod bent into a circular arc of radius r2=0.700 m that subtends an
arc of 90° about the center of the full circle with a net charge q2=-10.0 nC spread uniformly over its length;
and (0) two point charges of charge q3=+7.50 nC and q4=-7.50 nC, respectively, and located
symmetrically at a distance r3=0.500 m from the center of the full circle. (1) Write down the general expression forthe electric potential V V 2 K i
at a distance r from an isolated point charge q. ls V a vector r orascl ant't ? ’ ’ - h'
aarqu Iy K: gﬂgxmy ,v.M%Z V L5 5L ﬁat/Qaf (2) Use that expression to determine the electric potential that
the two point charges q3 and q4 produce at the center of the
full circle, individually and together. *7
\Jg : K ‘_ ((5)6 A709) M: +1’35” V ‘3) h (06%?)
V‘teK I —— (351/ v3 +V i5; (3) Determine the electric potential that the full circle of charge
produces at the center of the circle. amt/Q LVL»? XQM 3%? M+ @447 Hi (Ado/“C361 Cg: aid Maﬁa/“CL, 1—- } ’W 21r’ I ‘
0 ( R (4) Determine the electric potential that the quarter circle of
charge produces at the center ofthe full circle. . . , W2, .
SLLLLLJZMT'I} \ltt: / ALTLMQ_ K #2 M- (5) What is the total electric potential that all four charge-
carrying elements produce at the center of the circle? PHYS 0175 S rin 2008 —Worksheet Problem #4 PartB Your Name: KO 5 L E 12/) Score: Consider the following experiment with two hollow metal spheres: Sphere A has radius RA=10.0 cm and
holds a net charge qA=50.0 nC, and Sphere B has a radius RB=6.50 cm and is initially uncharged. The
two spheres are supported at rest on insulating stands and are separated by a distance that is large
compared to their radii. (1) Taking V=0 at inﬁnity, what is the electric potential V on the surface of each of these spheres? Vt 3“ g" : 4.5amcv‘3i/
V3 C7 \/ (2) Now the two separated spheres are briefly connected by means of a long copper wire that is thin
enough to retain only a negligible amount of charge. What can you say about the electric potential V
on the surface of each of these spheres after this contact by the wire? ( z: (Ll/“1431 fed- M4.th +030 waq (IA—6 (j +€L$2
gm, pa Larisa/Q . (3) Use your answer to (2) above to calculate the net charge on each of the two spheres afterthe contact
by the wire. (Hint: you will also need to apply a conservation law.) ( / ’ ( i
v’=<ié~:\/ «is, :> ELQBV /. at /
A W, B Q}, @A,'Eg~>?ﬁ“pg>$’e Bu} [Km/13L “Mgf Zea- (cmer-WX/ Coca/Lo; = 755,4 tﬂkeéi kg‘tc'i ,2,ch12, Ltcﬂx$ CM )ZKQ '_ My answers are: ...
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