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Unformatted text preview: PHYSICS 12 FIRST EXAMINATION JANUARY 29. 1992 Dr. Ralhs " 11:00 AM ' page 1 of 7
Km Rec. Instructor Grade ’1. _ Two signiﬁcant ﬁgures sufﬁce. 2. Exam is closed book. Calculators allowed. 3. Write your name legibly and your recitation instructor’s name on each page. 4. This examination has two sections: a) SECTION I IS THE LAB QUESTION.
It consists of one question. This question has about the same effect on your'coursc grade as
a 5point question in Section II. The scores on Section I will not be curved. b) SECI'ION II is the Midterm Examination.
It consists of 9 multiple choice questions and 2 problems (Problems BI and 32).
The scores on Section II will be curved. .5. Check now that you have a complete exam.
5. You have a total of 48 minutes to complete both sections. Values of pliysical constants:
Coulomb constant = 9.0 x 10' Nuisz2 co = 8.35 x 10"“ d/(Nm1)
c = 1.60 x 10"" C Page 2 of 7 4 Name I ' Rec. Instructor
SECTION I. LAB QUESTION This question worth 5 points. Circle the letter preceding the best answer. 1. The ﬁgure shows the oscilloscope screen as in lab. uerﬁ‘ul The quantity measured on the vertical axis is , and the quantity measured on the horizontal ‘ axis is . a electric force; displacement b potential difference; displacement
c potential difference; time potential difference; frequency
e ume; electric force 6 Name Page 3 of 7 Rec. Instructor SECTION II. MIDTERM EXAMINATION
Part A. Multiple Choice (5 points each). Circle the letter preceding the best answer. I. . A glas rod which has a net positive charge will attract which of the following objects? (Assume
that none of the objects 15 grounded) a only c) and d) below b all of the below _  c an uncharged wooden and: _
a rubber rod which has a net negative chairge e a woolen cloth which has a net positive arge Equations 2, 3. and 4 we consider two parallel conducting plates with equal but opposite charge I 0.10 M! a
I; x
0.10 m ‘ At which of the three locations marked in the figure is the potential highest? a) Depends on whether the test charge is positive or negative.
1)) A
c) B
d) C If the potential difference = 48 V between points A and C, then the electric ﬁeld at point B has
magnitude and direction:  a) 9.6 N/C ; +2
in) 9.6 N/C : 2
c) 240 N/C ; +2
d) 240 N/C ; £
e) 480 N/C ; +£ lithe capacitor show in the above figure has a capacitance = 4 it? and the potential difference
between points A and C is 48 V. what is the size of the charge 0 on each plate? a 8.3 x 10: C
1.9 x 10 C
4.6 x ‘10"3 C
.12 x to1 C
c none of the above Page 4 of ‘7 Rec. Instructor . _ . 5. ‘Whieh one of the following ﬁgures correctly shows the electric ﬁeld'lines? Assume the positive 6) 0.3% a: ,6) e) 6.. After ehargin g a parallel plate ea acitor that has air between the plates. the battery is disconnected
from the ca acitor. The space etween the plates is then ﬁlled mth paper that has dielectric
constant = Which one of the following statements is FALSE? The potential difference across the giates decreases.
The charge on the plates does not c ange. The electnc ﬁeld behaveen the plates decreases
The energy stored n the eapaextor increases. The eapamtanee increases. 0 05"” 9. Page 5 of 7 Rec. Instructor Whena toaster oven is plugged into a 120 volt outlet, the current passing through the coiis is 14
A. If the toaster oven 15 turned on for 30 3, how much eiectncal energy 15 converted to thermal b 17x10’W
c 1.7::10’1 2.4:: 10‘ J
c 5.0x10‘J A co er wire has a resistance of 0209. If the length of the wire and the diameter of the wire
were oth doubled, the new copper wu'e would have a res:stance of a 0.025 9
b 0.10 Q
c 0.20 9 0.40 9
e 1.6 $2 {kn isolated conductor has a net charge. In the static situation, which of the following statements
15 (are) TRUE? a Both c) and d) below are true. 1) All of the below are true. c The net charge is distributed on the outer surface of the conductor. ‘ The electric utenttal IS the same throughout the conductor. e Electn'c fie! lines are parallei to the outer surface of the conductor. Page 6 of 7 6 Name __,_______________ Rec. Instructor PART B. Problems BI and 32 must be worked in detail.s§HOlVMBBK to receive any credit for
correct answers. The value of the problem as own to parent e515. Bl. Charges Q1  5 pC and Q2  5 nc are placed as shown in the ﬁgure. a) ﬁaslculaic the electric ﬁeld (magnitude and direction) at point A. Include a vector diagram.
pts. b) Take the electric poterttial = 0 at an inﬁnite distance away from these 2 charges. Calculate
the potential VA at pom: A. (6 pts) c) If a charfge QJ = —7.0 C were placed at point A. ﬁnd the magnitude and direction of the
electric orce on 03. ('rpts.) Page 7 of 7 . Name Rec. Instructor 32;. gonﬁder the circuit shown in the ﬁgure. where R1 = 20 Q. R1 c 40 Q. R3 =2 60 Q. and V = 12 a) Compute the equivalent resistance R of the circuit. (8 1315) 13) Find the current I‘.
(5 1115) c) How much work is done by the electric ﬁeld in waving 4.0 C of positive charge from A to B?
(3 1315) 15) Find the current I .,
(8 pm) III. RALLIS: Jan. 29, 1992
Section I. *l. C
Section II Part A l. A 2. B 3. C 4. B 5 E
6. D 7 E 8. B 9. A
Part B 5
Bl. a) 4.8 x 10 N/C +x direction (if x points to the right}
b) O c) 3.4 N € ~x direction
132. a) 44.9— b) 0.27 A c) 22J d) 0.17A ...
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 Physics

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