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THE IUG DATE:27-3-2007 PHYSB 1301 FIRST MID EXAM. ………………………:الرقم الجامعي DEPT. OF PHYSICS TIME:1-Hr .……… ………………………………………:اسم الطـالب Part I Part II Q1 Q2 Q3 Total Q4 PART I: choose the correct answer 1) An insulator is a material a) containing no electrons c) through which electrons do not flow easily b) cannot be charged d) all of them 2) If e 1.6 10 19 C which of the following is acceptable charge? a) 210-19 C b) 110-19 C c) 0.810-19 C d) 1 C 3) Two point charges Q and –Q are located along the same line as shown. Where we can place a third charge q so that the net force on it is zero. a) between Q and -Q b) to the left of Q c) to the right of -Q Q -Q d) non of these q 4) Charges Q, -Q , and q are placed at the vertices of an equilateral triangle as shown. The net electric force on q is d -Q a) up bdown c) right d d Q d) left 5) A uniform electric field of E 2 109 i . The electric force F acting on a charge of -6C exists in this field is a) 12 103 i N b) 12 103 i N c) 3 103 i N d) 3 103 i N 6) A proton traveling east enters a region of uniform electric field that points west. The proton will a) speed up b) speed down c) go south d) go north 7) Choose the incorrect statement concerning the electric field lines a) field lines may cross c) field lines are tense where E is large b) field lines point away from positive charges d) the direction of E is tangent to field lines 2 8) Two point charges of 2Q and –Q are located as shown. The electric field will be zero at a point a) between the two charges only c) right to –Q only 2Q -Q b) left to 2Q only d) left to 2Q or right to -Q P 9) A rod of length 2a has a uniform positive charge. The direction of the electric field at point P shown in the figure is a a) up bdown c) right a d) left 10) A uniform electric field of E 24 i 20 j 16k is penetrating a plane of area 2 m2 and lying in the y-z plane. The electric flux through the plane is a) 32 N.m2/C b) 40 N.m2/C c) 48 N.m2/C d) 35 N.m2/C 11) The electric flux throught the curved surface of the cone is b) ER 2 d) ER 2 H a) 0 c) ER E 2 H R 12) A thin wire of length L has a uniform Q. Concentric with the wire is a hollow cylinder of length h. The electric flux through the surface of the cylinder is h L a) zero b) Q o c) QL h o d) Qh L o 13) A solid sphere has a nonuniform charge density given by r with r is the distance from the center of the sphere. The unit of the constant is a) C/m4 b) C/m3 c) C/m2 d) C/m 14) A point charge is placed at the center of a spherical shell. The electric flux through the surface of the shell will be increasedd if a) the radius of the shell is increased b) the charge is moved closer to the surface c) another charge is placed near the outer d) non of them surface of the shell 3 15) Which of the following is incorrect concerning a conductor in electrostatic equilibrium a) E inside is zero c) E on the surface is to the surface b) Q inside is zero d) V inside is zero 16) An electron is accelerated from point A to point B in a uniform electric field E. If the distance between A and B is d, then V VB V A is a) Ed b) -Ed c) E/d d) –E/d 17) Two concentric spherical shells of radii a and b are charged to a total charge Q. The electric potential on the inner shell is a b a) zero b) K Q a c) K Q b d) K Q r 18) The electric potential at a point P is 8×103 V. The work required to bring a charge of -2C from to P is a) 16 mJ c) 4 mJ b) -16 mJ d) -4 mJ 4 PART II: Solve the following problems Q1) a small charged ball of mass 5 g is suspended by a 0,5 m long string in a uniform electric field of 100 N/C as shown. If the ball is in equilibrium when the string makes a 15o with the vertical, what is the charge on the ball? Q2) A thin rod having a uniformly distributed charge q is bent in a quarter circle of radius R as shown in the figure. Find the electric potential V at point P, the center of the circle. 15o E y q R p x 5 Q3) A solid conducting sphere of radius a has a charge Q. Concentric with this sphere is a thin spherical shell of radius b and a net charge Q. Find the electric field at (a r b). Q -Q a b Q4) Referring to the previous problem, Find the electric potential at a point inside the sphere (r a ).