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University of the PhilippinesCollege of SciencePhysics 72Set AFirst Long ExamSecond Semester, AY 2014–2015Name:Instructor:Section/Class Schedule:Student Number:Course:College:
First Long ExamSecond Semester, AY 2014–2015Physics 72INSTRUCTIONS:Choose thebestanswer 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:AreaVolumeSphere (radius=r)4πr243πr3Cylinder (radius=r, height=h)2πr2+ 2πrhπr2hsin(π/3) = cos(π/6) =√3/2cos(π/3) = sin(π/6) = 1/2sin(π/4) = cos(π/4) =√2/2Useful constants:e-1.60×10-19Cme9.1×10-31kg08.854×10-12C2/Nm2k8.988×109Nm2/C21.Square.Consider the point charge distribution in the fig-ure. What is the magnitude of the net electric force on thecharge+q0that lies in the center of the square?A.4kqq0a2B.8kqq0a2C.2k(q+Q)q0a2D.4k(q+Q)q0a22.E and F .A source charge+|Q|and a test charge-|q0|are separated by a distancer.Which of the following is/areTRUEabout the electric fieldEand electric forceFEof+|Q|on-|q0|?I.FEandEhave the same direction.II.FEandEhave opposite directions.III.|FE|and|E|are inversely proportional to one another.A – 2
First Long ExamSecond Semester, AY 2014–2015Physics 723.Magnitude.Consider the diagram showing the equipo-tential lines around two identical positive charges. Whatis the relationship of the magnitude of electric field at thedifferent points?4.dipole.An electric dipole is oriented in the uniform elec-tric field with magnitude200N/Cas shown. What is themagnitude and directionof the net torque experiencedby the electric dipole?5.Plastic and Fur.A plastic rod (+) is rubbed on fur (-). Two balls X and Y are suspendedby insulating threads. The observations are as follows:I. Both X and Y are attracted to the plastic rod.II. X is attracted to Y.III. Y is repelled by the fur.Which of the following isTRUEregarding the system?A. X: neutralB. Y: neutralC. X: (-)D. Y: (+)A – 3
First Long ExamSecond Semester, AY 2014–2015Physics 72