Physics 72 First Long Exam

University of the PhilippinesCollege of Science

Physics 72

Set BFirst Long Exam

Summer, AY 20132014

Name: Instructor:

Section/Class Schedule: Student Number:

Course: College:

First Long Exam Summer, AY 20132014 Physics 72

INSTRUCTIONS: Choose the best answer and shade the corresponding circle on your answersheet. To change your answer, cross-out and sign your original answer and then shade yournew answer. No computational devices allowed (e.g. calculators, mobile phones). Any formof cheating in examinations or any act of dishonesty in relation to studies, such as plagiarism,shall be subject to disciplinary action. Following instructions is part of the exam.

Useful formulas:

Area VolumeSphere (radius=r) 4pir2 43pir

3

Cylinder (radius=r, height=h) 2pir2 + 2pirh pir2hsin(pi/3) = cos(pi/6) =

3/2

cos(pi/3) = sin(pi/6) = 1/2sin(pi/4) = cos(pi/4) =

2/2

Useful constants:

e 1.60 1019 Cme 9.1 1031 kg0 8.854 1012 C2/Nm2k 8.988 109 Nm2/C2

1. Grounded Ka. An uncharged conducting cube is initially grounded as shown in the figure.A rod with charge +3q is brought near a cube, and then the cube is disconnected from theground as shown. What is the FINAL CHARGE of the cube?

A. +6qB. +3q

C. ZeroD. 3q

E. 6q

2. AttractX. A negatively charged plastic rod attracts object X . Similarly, a positivelycharged glass rod attracts the same object. Which of the following is/are ALWAYS TRUEabout object X?

I. It can be a conductor or an insulator.

II. It is an insulator.

III. It is uncharged.

A. I onlyB. II only

C. III onlyD. I and III only

E. II and III only

B 2


3. Madaming Planes. Three charged INFINITE PLANES that are parallel to each other areshown. Which of the following correctly relates the MAGNITUDE of the electric field atthe four regions?

A. E1 < E2 < E3 = E4B. E1 < E2 < E3 < E4C. E1 > E2 = E3 > E4

D. E1 = E2 = E3 = E4E. E1 = E2 < E3 < E4

4. Cruxify. Consider the system of point charges shown.What is the direction of the NET ELECTRIC FORCEexperienced by the negative point charge at the origin?Note: q > 0.

A. +x-direction

B. +y-direction

C. x-direction

D. y-direction

E. zero net electricforce

B 3


5. Parisukat. Consider 4 point charges positioned in thecorners of a square. In which locations is the net elec-tric field produced by the point charges points toward theNEGATIVE X-DIRECTION?

A. II only

B. I only

C. IV only

D. I and II only

E. III and IV only

6. SVA. A stationary charged particle is placed in a UNIFORM ELECTRIC FIELD. Whichof the following statements is/are TRUE about the particle?

I. It will move at a constant velocity.II. It will move at a constant acceleration.

III. It will experience an electric force.

A. II onlyB. I only

C. II and III onlyD. I and III only

E. III only

7. ETorque. An electric dipole is immersed in a uniformelectric field with magnitude E and directed downwardas shown. What is the MAGNITUDE of the torque ex-perienced by the dipole and in which DIRECTION willit rotate?

A. eaE2 , clockwise

B. eaE2 , counterclockwise

C.2eaE2 , clockwise

D.2eaE2 , counterclockwise

E.3eaE2 , clockwise

8. Guadrawn. A cylindrical NON-CONDUCTING shell has an inner radius a and an outerradius b. It carries a uniform charge density. Coaxial to the shell, a cylindrical Gaussiansurface with radius a < r < b and length L is drawn. What is the charge enclosed by theGaussian surface?

B 4


A. [pi (r2 a2)L]B. [pir2L]C. [pi (r2 b2)L]

D. +[pi(r2 a2)L]

E. +[pir2L

]

9. Kahon-Lata. A cylinder which contains a positive pointchargeQ is placed inside a box. Inside the box is anotherpoint charge 2Q. What are the electric fluxes throughthe cylinder and the box, c and b, respectively?

A. Q0 ,Q0

B. Q0 ,Q0

C. Q0 ,Q0

D. Q0 ,2Q0

E. Q0 ,2Q0

10. GuaGua. The charged particles are arranged inside and outside a cylinderas shown in the figure. What is the total electric flux through the cylinder?

A. 4q0B. 3q0

C. +3q0D. +4q0

E. +8q0

11. SaBilog. Consider a spherical conductor with net charge+q. A particle with charge +3q is placed inside the cav-ity as shown in the figure. What is the electric charge onthe outer surface of the sphere?

A. 4qB. q

C. 0

D. +q

E. +4q

B 5


12. Encircle. Consider two concentric spherical CON-DUCTING shells as shown. The inner and outer shellsboth have a net charge of 2Q. If a point charge Q isplaced at point P , in which regions is the electric fieldRADIALLY INWARD?

A. 2 and 4 only

B. 3 and 5 only

C. 1, 3 and 5 only

D. 5 only

E. 1 only

13. Locus. Positive electric charge Q is uniformly dis-tributed throughout the volume of an INSULATINGsphere with radius R. Which of the following is thecorrect relation of the magnitude of the electric field atpoints A, B and C?

A. EA = EB = EC

B. EA = EC < EB

C. EA = EC > EB

D. EA < EC < EB

E. EA < EB < EC

14. NegPathive. A negative point charge is moved alongeach of the paths shown. In which of the following pathsis the work done by the electric field equal to ZERO?

A. 3 only

B. 2 only

C. 1 only

D. 1 and 3 only

E. 1 and 2 only

15. Feel na Field. Which of the following statements is/are TRUE about the electric force?

I. It is a conservative.

II. The work done by the electric force can be associated with a negative of the change inpotential energy.

III. The work done by the electric force is path dependent.

B 6


A. I onlyB. II only

C. III onlyD. I and II only

E. II and III only

16. WorkingSphere. Consider a solid conducting spherewith radius R and total charge +Q. What is the workdone by an external force in moving a positive pointcharge +q from point A to point B?

A. +kqQRB. kqQR

C. +kqQ2RD. kqQ2R

E. Zero

17. QWork. The work done by the electric force in moving a negative point charge q0 (q0 R2, which ofthe following is/are TRUE?

I. I1 > I2

II. I3 = I4

III. Vcd > Vef

IV. Vab = Vcd

A. II, III and IV onlyB. I, II, III and IV

C. II and IV onlyD. I, III and IV only

E. I and III only

36. Resistensya. Consider three resistors that are connectedin circuit as shown in the figure. The total current thatflows from terminals A to B is 2.00 A. What is the po-tential difference between terminals A and B?

A. 8.00 V

B. 10.0 V

C. 20.0 V

D. 30.0 V

E. 50.0 V

37. Resten. Ten resistors each with resistance R = 1 k are connected in series. The combi-nation is then connected to a 10 V power supply. What are the current through and voltageacross one of the resistors?

A. 1 mA, 1 VB. 10 mA, 1/2 V

C. 10 mA, 5 VD. 100 mA, 1/5 V

E. 100 mA, 2 V

38. RCBilis. In which of the following values of resistance R and capacitance C is the capac-itor in an RC circuit charged the fastest?

A. R = 2 M, C = 1 nFB. R = 1 k, C = 1FC. R = 4 k, C = 1F

D. R = 4 k, C = 2F

E. R = 4 M, C = 1/4F

39. Rationale. Two power supplies and a resistor are connected in each of the two circuitsshown. What is the ratio of the power generated by the 12.0 V power supply in circuitsI and II (P12,I/P12,II)? Neglect the internal resistance of the power supplies.

B 12


A. 5B. 3

C. 1D. 1/3

E. 1/5

For the next two items, consider the circuit shown.

40. Paliguy-ligoy1. What is the current through resistor R?

A. 1/4 AB. 1/2 A

C. 1 AD. 2 A

E. 4 A

41. Paliguy-ligoy2. If the circuit is broken at point x, what is the current through R?

A. 1 AB. 10/9 A

C. 5/3 AD. 2 A

E. 4 A

B 13

Documents

Physics 72 First Long Exam