p117b_07_prim_ans

p117b_07_prim_ans - Physics 117 B Sec 1 (Prof. Csorna)...

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Unformatted text preview: Physics 117 B Sec 1 (Prof. Csorna) 4/28/07 9:00 AM Primary Final Formulas and Constants: A pair of charges conducting plates produces a uniform field of 12,000 N/c, directed to the right, between the plates. The separation of the plates is 40 mm. 1) In the figure above, an electron is projected from plate A, directly towards plate B, with an initial velocity of v0 = 2.0 x 10 7 m/s. The velocity of the electron as it strikes plate B is closest to: A) 1.2 x 10 7 m/s B) 1.5 x 10 7 m/s C) 1.8 x 10 7 m/s D) 2.1 x 10 7 m/s E) 2.4 x 10 7 m/s ans B Figure 22.3 2) Two hollow conducting spheres have a common center O. The dimensions of the spheres are as shown. A charge of - h nC is placed on the inner conductor and a charge of + h nC is placed on the outer conductor. The inner and outer surfaces of the spheres are respectively denoted by A, B, C, and D, as shown. In the figure above, , the charges on surfaces A and B respectively, in nC, are closest to: A) 0 and - h B) 0 and - h C) 0 and - h D) - h and - h E) - h and - h ans A 3) In a given region the electric field is constant and has the value 100 V/m. It points in the positive xdirection. If the potential at the point x = 4 cm on the x-axis is 6 volts, what would be the potential at the point x = 16 cm? A) -22 V B) -18 V C) -10 V D) -6 V E) +6 V ans D 4) Each plate of a parallel-plate air capacitor has an area of øT v · ªw m 2, and the separation of the plates is 6 ø T v ·ª mm. An electric field of h x 10 V/m is present between the plates. The energy density between the plates is closest to: A) h J/ h 3 B) h J/h 3 C) h J/h 3 D) h J/h 3 E) h J/ h 3 ans A 5) In the figure above, the four identical capacitors in the circuit shown here are initially uncharged. The switch is thrown first to position A and then to position B. After this is done A) V1 = V2 = V3 = V4 B) V1 = V0 C) V1 +V2 + V3 + V4 =V0 D) Q1= 3 Q2 E) Q1=Q2 ans D A multiloop circuit is given above. Some circuit quantities are not labeled. It is not necessary to solve the entire circuit. 6) In the above figure, the current I1 is closest to: A) zero B) +0.2 A C) +0.4 A D) -0.2 A E) -0.4 A ans B hV h hF h Mh 7) Initially, for the circuit shown above, the switch S is open and the capacitor is uncharged.The switch S is closed at time t = 0. At a given instant, the potential difference across the capacitor is twice the potential difference across the resistor. At that instant, the charge on the capacitor, in hC, is closest to: A) h B) h C) h D) h E) h ans A h A he B= h T 8)A rigid rectangular loop, which measures 0.30 m by 0.40 m, carries a current of h A, as shown above. A uniform external magnetic field of magnitude h T in the negative x-direction is present. Segment CD is in the x-z plane and forms a h 0 angle with the z-axis, as shown. An external torque applied to the loop keeps it in static equilibrium. The magnitude of the external torque is closest to: A) h N m B) h N m C) h N m D) h N m E) h Nm ans A 9) As shown above, a rigid circular loop has a radius of 0.20 m and is in the x-y plane. A clockwise current I is carried by the loop, as shown. The magnitude of the magnetic moment of the loop is 0.75 A m2. A uniform external magnetic field, B = 0.20 T in the positive x-direction, is present. The current in the loop is closest to: A) 3.0 A B) 4.5 A C) 6.0 A D) 7.5 A E) 9.0 A ans C 10) In the figure above, a view of a solenoid, showing the clockwise sense of the current in the windings, is given. The magnitude of the field is 1.5 x 10-3 T. An electron is in circular motion near the center of the solenoid, with an orbital diameter of 3.0 cm. The speed of the electron and the sense of the orbital motion are closest to: A) 4 x 106 m/s, clockwise B) 6 x 106 m/s, clockwise C) 8 x 106 m/s, clockwise D) 4 x 106 m/s, counterclockwise E) 10 x 106 m/s, counterclockwise ans A 11) As shown above, a wire is bent into the shape of an Omega, with a circular loop of radius 4.0 cm and two long straight sections. The loop is in the x-y plane, with the center at the origin. The straight sections are parallel to the x-axis. The wire carries a 5 A current, as shown. The magnitude of the magnetic field at the center of the loop, in hT, is closest to: A) 25 B) 40 C) 55 D) 80 E) 105 ans C 12) In the figure above, a bar magnet moves away from the solenoid. The induced current through the resistor R is: A) zero B) from a to b C) from b to a ans B 13) In the figure above, one end of a bar is in contact with a circular rail and the other end is pivoted at P. A steady, uniform, magnetic field B is present. The bar rotates about P. The induced current through the resistor R is: A) zero B) from a to b C) from b to a ans C 14) hH hh R-L circuit has a 60 V battery, a h H inductor, a h ohm resistor, and a switch S, in series, as shown. Initially, the switch is open, and there is no magnetic flux in the inductor. At time t = 0 s, the switch is closed. The rate of change of the current when the current is 1.5 A is closest to: A) h A/s B) h A/s C) h A/s D) h A/s E) h A/s ans A 15) A planar electromagnetic wave is propagating in the positive x-direction. At a certain point P and at a given instant, the electric field of the wave is given by E = -j h mV/m. The Poynting vector at the point P at that instant is closest to (i,j,k are the usual unit vectors): h h Y v˜ · ª A) h Y v ˜ · ªw h h h Y ˜v · ªw B) h Y ˜v · ªw h C) h Y ˜v · ªw D) h Y v ˜ · ªw E) h Y ˜ v · ªw ans A 16) h Y ˜v · ªw h Y v ˜ · ªw h h Y ˜ v · ªw h h h h h h m h m A tank holds a layer of oil, h m thick, which floats on a layer of syrup that is h m thick. Both liquids are clear and do not intermix. A ray, which originates at the bottom of the tank on a vertical axis, crosses the oil-syrup interface at a point 0.90 m from the axis. The ray continues and arrives at the oil-air interface, 2.00 m from the axis and at the critical angle. In the above figure, the index of refraction of the syrup is closest to: A) h B) h C) h D) h E) h ans A 17) When an object is placed 30 cm from a converging lens, the image formed is positioned 60 cm from the lens. If the object is moved 5 cm closer to the lens, the position of the image changes by 40 cm. What is the focal length of the lens? A) 16 cm B) 32 cm C) 36 cm D) 20 cm E) 25 cm ans D 18)A 360 nm thick oil film floats on the surface of the water. The indices of refraction of the oil and the water are 1.50 and 1.33, respectively. The surface of the oil is illuminated from above at normal incidence with white light. The two wavelengths of light in the 400 nm to 800 nm wavelength band that are most strongly reflected, in nm, are closest to: A) 410 and 700 B) 430 and 720 C) 450 and 740 D) 470 and 760 E) 490 and 780 ans B 19) A single slit forms a diffraction pattern, with the first minimum at an angle of 400 from central maximum. Monochromatic light of h nm wavelength is used. The same slit, illuminated by a different monochromatic light source, produces a diffraction pattern with the second minimum at a 600 angle from the central maximum. The wavelength of this light, in nm, is closest to: A) h B) h C) h D) h E) h ans A 20) A photocathode has a work function of h eV. The photocathode is illuminated with monochromatic radiation whose photon energy is h eV. The maximum kinetic energy of the photoelectrons produced is closest to: hh A) W v x · ª w hh B ) W xv · ª w C ) W xv · ª w h h D) W v x · ª w h h E) W x v · ª w h h ans A ...
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