physics 2

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Physics2205 Final Exam PRACTICE University of New Haven Fall,20l7

7-Dec-2017

This exam is open book and open notes and calculators are allowed, but you may not acce$s the internet. Please no talking during the exam. Total Points: 200

Each Multiple Choice nroblem is worth 6 noints.

,fi. t J 1. A pF.pV is equivalent to a\-1 u a. mT b. pC c. nC e.pN f. nJ Bulb I Bulb 2

2. The circuit in the figure above contains two identical lightbulbs in series with a battery. At first both bulbs glow with equal brightness. When switch S is closed, which of the following occurs to the bulbs?

Bulb 2 Gets brighter

/ Goes out Gets slightly dimmer Gets brighter

"/ Goes out

'/--L V r& ,> lt

ar^. rkz ,t a{ avttl )rnu -

B (into page)

xxxxx -r}xr) r\* ,^\yx

4. A wire ,"", ;;r) ,*t .U in a time-varying but spatially uniform magnetic field that is perpendicular to the plane of the loop, as shown above. The induced emf in the loop is given by e :

3. A bar magnet and a wire loop carrying current "1" are arranged as shown above. In which direction, if any, is the force on the current loop due to the magnet? Assume a perfectly circular loop.

a. Toward the magnet 57nra<.?t\t,tle-b. Away from the magnet lvD. Away rom Tne magnet f I eer{eo(l-t tyll^rrc. Toward the top of the page r^ L { r - ' '

d. Toward the bottom of the page \ -(on.. r s ovhual <4-.rnere is no force on the current loop

/ po,- ar^. rkz

b&tr/2, where b is a constanglhe time varying magnetic field could be given by

(x) !utr''' @:u,-''.' G)

!tt''' (o) ?u.qt'''

blil -''

"! r,l r-t' = A #

(n) ? u'''

?

E 4t

Bulb I -.- a. Goes out

,r"{a}>cets brighter .'' c. Get brighter d. Gets slightly dimmer e. Nothing

Se< {^btz Z<t.\ 5. The capacitance of a pure water-filled parallel-plate capacitor with plate area .024nf and separation

0.030-mm is

@ro,r b. 62tlF c. 27 1tF d. 26mF e. 7.0 F

==

k z"/T (g o.'t\ ( s.8s r to-'-\ ('o>v)

?*t o -J

= 5-t ,rf,? F

6. A +50 pC charge moves vertically upward at 100 m/s. Which magnetic field will produce a northward magnetic force of 10 mN?

a. 5.0 T, South b. 12.T,North c. 2.5 T, East

ius of curvature of an electron moving at2xl0s m/s in a 400 T uniform magnetic field is .8 nm (q.t4 o-rr)(z*ro t) _t

= 2.6tto[L= (i.e*t"-r{) /voo)

system. What effect does this have on the capacitance?

Gltcauses the capacitance to increase. It causes the capacitance to decrease. None; the capacitance does not change. Nothing can be said about the effect without knowing the dielectric constant of the plastic. Nothing can be said about the effect without knowing the thickness of the sheet.

f=4Y8r,".0 ^ I.ol l.Ie t u; *- /;ffi-) -

I , ?'6

_(L

40 nm 540 mm 8.3 cm 2l cm

n>Y.p

*

-Jil l-'d.u

(Q 8&9) A capacitor is constructed of two identical conducting plates parallel to each other and separated by a distance d. The capacitor is charged to a potential difference of Voby a battery, which is then disconnected.

8. If any edge effects are neqligihlp, what is the magnitude of the electric field between the plates? (A)V"d @w (C)d/vo (D)v"/d2 (E)v"2/d

9. A sheet of insulating plastic material is inserted between the plates without otherwise disturbing the

flll 'r'st^\'t'nl'wfit b. c.

d.

++ 6Y;\- XX

10. Two initially uncharged conductors, I and2, are mounted on insulating stands and are in contact, as shown above. A negativelyrharg"dffdis brought near but does not touch them. With the rod held in place, conductor 2 is moved to the .ight by pushing its stand, so that the conductors are separated. Which of the following is now true of conductor 2?

a. It is uncharged b- It is positively charged

@t is negativeiy charged d. It is charged but the sign cannot be predicted. e. It is at the same potential that it was before the charged rod was brought near.

Fc

tr'ree Response Section: For full credit, complete four of the five problems. The four problems are worth 35 points each. The fifth problem can be completed for up to L5 extra points. PLEASE CLEARLY MARK WHICH PROBLEM IS YOUR EXTRA-CREDIT PROBLEM. (Otherwise the assumption is that the extra-credit problem is problem 5).

1. Consider the following circuit of light-bulbs. The voltages and resistances are as given. The brightness

6: 12.0 Y R1:ft2:ft3-Rt:6.0 d)

Find the value for a single light-bulb power rating (12V). Find the equivalent resistance Rank the light bulbs in terms of their brightness.

L Kp

a.

b. c.

(")

l.p 6l

4= 4+6=

Fr,'1141,ra sS f v>Pur*rbxa

(,-"n<* S'bl/owt s l<ad

(t)

e)

t3l tz q*-

.J-

/ to CtalY*?tt

16frffarC( -

of a light-bulb depends the amount of current going through it.

Ep

65rs$

2. The system of capacitors is connected to a battery with potential difference Vuu:25.0V. a. What is the equivalent capacitance of the circuit? b. How much charge is stored by this system? c. How much charge does the 6.5-nF capacitor store? d. What is the potential difference across the 7.5-nF capacitor?

(4

(t;

(.)

(a>

v=* Q=cV =- (n.^? rto-{r)(=r v;

=

,j-- cv= (e s^rJl ,.-t\

=

I

(-5 -

3. A long straight wire lies along the y-axis and carries a current I:8.00 A. In addition to the field produced by the wire, there is an additional field, a uniform magnetic field with strength Bo:1.5pT in the x- direction.

a. What is the total field (magnitude and direction) at the point (0.0, 0.0, 1.0m) (point a). b. What is the total field (magnitude and direction) atthe point (1.0m, 0.0, 0.0) (point b).

,, c. What is the magnetic force on a proton at point c: (0.0, 0.0, -0.25m).

4F.

('Y- /'ttt"r''J u) -7fl=

(u> --7B ur.n >

-) Bt=

t.L*r G)

l . 56113? + -

| . r[br) z

Dv<dr-* '

tanO =

Q=

t.L

G 4 6-8" fro^ 7^o*'s

llir,ll -@

vr> - 2*k<e ,^ +'J';V-

6 .,1,f t,^ tX'-/'c

7s"" f,1"* a't-v<')

rzilu .n (e) fr"'rd ne<d; lo b< 'lufr^"dl-

l€ v--o {6e< =o ' Asrr rr* V'- /*'/s?L t'v1 +!'''t'a ' " ' 'r;ll

f= O '

4sr^w-z

8n,* =

Br= I 1*T "^ i-l-l..c.

-:I i =z-srr-'YN (+'f-lI

7.1rrt' ) '"-(oJ) (i\

4.

E:48.0 V Rt:Rz:6,0 {2 L:0.2 H

Consider the following circuit with values as given. a. Write (but do not solve) an equation for the Kirchoff Junction Rule relevant to this circuit.

Assume the switch is closed. b. Write (but do not solve) two separate equations using the Kirchoff Loop Rule for this circuit.

Assume the switch is closed. c. Just after the switch is closed, determine the currents in the circuit. d. After a very long time, what are the currents in the circuit?

(a\

e f' R' - T'P'= o

{, R, L=O

(") uuk, , tt-J\tcl'. i s i"l clos'd'

'

U\ I Ptn- /o^,1 tir>-a, frlo, tj = eg Lr) = €=

f+g- -= V/R,tR-- I l

,.$

rli)r

liqhl c'n's ?l^rs

gd'l

- -

r'i 1- - -,',,{ \ i ,i io tn,rfr.1ri,,o ,,,,,"* {-j' :i-,t " l t:,r ll ff t-i.,1 ;nr I : it'\, l\\,r\

tr\

Consider the two lenses above. h? I' E a a. Find the focal length of the left lens (Assume the radius of curvature of the right edge is infinity). b. Find the image distance and the magnification for an object a distance of 30 cm from the left lens

(and on the left side of the lens). Assume the right lens is not present. c. .Find the focal length of the right lens. d. Find the magnification of an object place 12.0 cm to the left side of the right lens. Assume the

] 3o

t- t-+= J- -,: = * Ctl

5.

(^)

(L)

+= (ast( ct.t e4 )f- \

d- (usf(;= -,+)

left lens is not present.

5,? ' n-

0J1} (' tu\5.2 r<

f /: f-J .3 c w''- -sl'"t ^1}8yn: fr a-

L,l_ I f ' ,t - f

J- 17.)-

_ -8.66e d"Yx,-S

L' 9-3

(c)

(a> !r l { ' tt

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