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Unformatted text preview: PHY204 UNIT EXAM 3 Nov. 23, 2007  Name Problem 1 An electron (mass m = 9.] 1x10‘31 kg, charge q = l.6x10'19 C) has a speed V =
2.0x107 m/s when it enters (at point A) a region of magnetic ﬁeld B directed
perpendicular to the plane of the sheet. The ﬁeld provides a centripetal force of magnitude F: 5.0x 10'15 N that bends the path of the electron into a semicircle of
radius r, as shown. (a) Find the magnitude 3 of the magnetic ﬁeld. (b) Find the radius r of the circle. (0) liind the speed VI of the electron as it exits the region
ofmagnetic ﬁeld at point (7. (d) Find the direction (out ofthe plane; or into the plane)
ot‘the field B. %ya, F:
ii (a) B t: 1,5; ruf’ﬂ 2x107 I?” :2! “diff/ﬂ‘wL‘E/ ll CT“. [9 : _, g
“i ( ) r F 5" lOJ/T
rﬁi/ V— ‘ ﬁ—é— , 1/
m w
(ill vzromd, _ V! :szsgo T,
(d/ f; (gm/2 ; 5 <9 mag/aw
l ()“r‘ 69 " I“) Problem 2 A very long, straight wire at x = 1m carries current 11 = 6A, and a second
long wire at x = 3m carries current 13 = 3A. The current directions are as
shown. Find magnitude and direction {up/down/right/left/into plane/out of
plane) of the magnetic ﬁeld (a) 30 at x = 0; I l= 6A I3= 3A
(1)) B; atx = 2m;
(c) Bi atx = 4m. (7 (kaoufé {1/9” W 94"!”{CA‘2L1 afﬂ/DOII‘B‘L/Q» 8' B :4": _£ 3:; r  __é 3 0 92,7 ,ZK/U // + 3
[30 wamw‘g'x‘r—AO/T/ 5’0
(o 8 251* I4 1 " .  ,
K j 2, ’27 +(lm)) 2m; /(+§/,/,8Ar/0
r52 7+/,3://¢A T/'_‘ [32 7 2] {41/ Beg" £133 : ’ “320.: Problem 3 A conducting square frame with sides of length L = 2m and electn'cal resistance R
= 100 is placed in the yzplane as shown. A unifonn magnetic ﬁeld B = Bxi is
applied perpendicular to the yzplane. The dependence of B,i on time t is shown
graphically. Find magnitude and direction (cw/cow) of the induced current I (a) at timer: Is; 2 BAT]
(b) at t1mer=3s. 3
3 21
4 2m 0
A
(broom A =/lg (600 Y 1 1 2 3
2 A=4>rw X Fiﬁ/(acea/ C6"? "TEL 7/ ﬁr, LE ~Z’
(a) M t S (7H , LS 0,5 5
£1 ~4M5’: ~30 V; CW
"’ g— ——’g':"' A 11:72] ’ l0 /
Midi ; {I
(lo/Au #225 27,02? A 3
5M t[s] ...
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This note was uploaded on 04/07/2008 for the course PHYS 204 taught by Professor Andrevantonder during the Fall '07 term at Rhode Island.
 Fall '07
 AndrevanTonder

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