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Physics 6B Practice Final

# Physics 6B Practice Final - Physics 68 Practice Final 1 Two...

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Unformatted text preview: Physics 68 Practice Final 1. Two speakers placed 4m apart produce sound waves with frequency 4251iz. A iistener is standing 3m in front of the left speaker. Describe the sound that he hears. Assume the speed of sound is 340 m/s. a) he hears a loud sound (constructive interference) ‘ * ' ‘ ' ' ‘ ‘ ‘ Erh— “““““ ' 1)) he hears a quiet sound (destructive interference) y & c) neitherconstructive or destructive interference - d) he runs away screaming like a little girl. 2. Charge 0,, = ~5.4p.C is placed at the origin, and charge q; W -2.2 uC is on the x—axis at x=lm. Where should a charge q; be placed between q, and q; so that the net force acting on it is zero? a) x=0.20 in h) x=0.42 m c) x=0.61 m d) x=l.2 in 3. An object with a charge of we 3.6;:(1‘ and a mass of 12g experiences an upward electric force, due to a uniform electric ﬁeld, equal in magnitude to its weight. Find the direction and magnitude of the electric ﬁeld. a) 33,000 N/C upward b) 33,000 N/C downward c) 33,000 MC to the right d) 66,000 N/C downward 4. Two conducting spheres have net charges q1=+8 cc and q2-~~2 54C. The spheres touch and some charge is transferred. How many electrons are transferred, and to which sphere? a) 3.1x1013 electrons are transferred to sphere l h} 3. 1x1013 electrons are transferred to sphere 2 0) 5x106 electrons are transferred to sphere 1 d) 5x106 electrons are transferred to sphere 2 5. During a lightning strike, electrons are transferred ﬁ‘om the bottom of a thundercloud to the ground. During this process, the electrons: a) gain potential energy as they move toward a higher potential b) lose potential energy as they move toward a 10wer potential c) ga'm potential energy as they move toward a lower potential d) lose potential energy as they move toward a higher potential 6. During a lightning strike, electrons are transferred from the bottom of a thundercloud to the ground. This occurs due to dielectric breakdown of the air, when the electric field is greater than 3x106 Wm. The distance from the ground to the cloud is 1000111. Find the magnitude of the potential difference between the cloud and the ground. a) 3000 V a) 3x106 V 0) 9x106 V d) 3x109 V 7. An electric dipole consists of two equal charges, +q and —q, a distance d apart. Find the total electric potentiai at a point that is a distance of d/2 to the right of the positive charge, as shown. a) kq/d b) qu/d 'q d "”1 (1/2 c) (4/3)icq/d O<----———--——-—-——>O<—,——-—> a) (1/2)kq/d 8. How much charge is on each plate of the capacitors in the circuit shown? The battery has voltage 12V, and the capacitances are: Cf—"SgF, Cf—QpF, C3=4pF_ a) Q1: 24 MC; (22:8 MC ;Q3=16 11C i3) Q1“ 24 RC; Q2WE6 pC ;Q3=8 MC C 0) Q1” 12 “C; sz4 ac £2338 pC 12 2 d) Q1” 12 11C; QﬁS MC £23316 #C C1 Cs 9. A parallel—piate capacitor is initiaily charged by a battery with voltage V. The battery is disconnected, and a dielectric with constant k is inserted between the plates. What happens to the energy stored in the capacitor? a) The stored energy increases by a factor of k2 " b) The stored energy increases by a factor of k c) The stored energy decreases by a factor of k d) The stored energy decreased by a factor of 2k E0. How much power is dissipated in each of the resistors'in the circuit shown? The battery has voltage 12V, and the resistances are: RIMQ, R2W3Q, Rgreﬁﬂ. 1 2 R2 i , i 31 .w. Re. a) P1=i6 W; P2=5.3W; P3=2.7W b) Pg=16 W; P2=3W; P3=3W c) P1=i6 W; 132:1.5W; P3=4.5W d) 131:4 W; P2=6W; P3=2W 11. in the circuit below aii the buihs have the same resistance. When the switch is closed, what happens to buib A? cg: a) Buib A gets brighter A b) Bulb A gets dimmer J c) Bulb A remains the same (1) Ruth A gets burned out by physics 12. Resistor l is a soiid cyiinder with length L and diameter D. Resistor 2 is made of the same material, but it has length 2L and diameter 21). Compared to the resistance of resistor l, resistance 2 is: a) twice as large b) half as large c) the same (i) four times as large 13. A coii with 1000 turns of wire and a crossvsectional area of 0.51312 is rotating at 60min in a uniform magnetic field of magnitude 2 Teslas. Find the voltage induced. in the coil as it rotates through one quarter of a revolution?. a) 409W b) many 0) 120V d) 240V 14. Two singly ionized isotopes of uranium (one electron has been removed) are projected at v=l.5x105rn/s into a region with a uniform magnetic ﬁeld of strength 075T directed into the page, as shown. The particles Eand at distances d1=68.2crn and d2=69.2cm from the entry point. Find the difference between the masses of the particles. ‘8 ® ® ® a) 4x10‘25kg h) Ix10“25hg c) exiomkg - d) ixiomkg ® ‘8’ ® ‘8 s» «a ,,-——®\ :3: e @@ e " e 2 1 V 15. Consider the three eiectric charges shown heiow. Charge B is equidistant from charges A and C. List the charges in order of the magnitude of the force they experience, from smallest to largest. a) A, B, c .. + + b) A, C, E (q) {51 C31 0) C, A, B d) C, B, A A B C 16. A beam of electrons is passing through a region with a uniform magnetic ﬁeld directed into the page. If the electrons are initially moving in the in}: direction, which direction are they deflected when they enter the ﬁeld? a) the electrons are deﬂected into the page b) the electrons are deﬂected downward c) the electrons are deﬂected upward d) the electrons are not deﬂected E7. A circuit is arranged with a sliding wire that can move vertically, as shown. There is a uniform magnetic field directed out of the page. The siiding wire is released from rest in the position shown. As the wire falls: 3.) induced current fiows clockwise in the circuit and the bulb gets brighter and brighter. @ 1)) induced current flows clockwise in the circuit and the bulb glows with a constant brightness. 0) induced current ﬂows counter-clockwise in the circuit and the buib gets brighter and bright . d) induced current flows counter—clockwise in the circuit and the bulb glows with a constant brightness. @ @ £8. A metai ring is falling toward a wire with a steady current ﬂowing to the right. What direction is the induced current in the ring? a) clockWise b) countenclockwise © l V c) there is no current induced in the ioop d) the ring bursts into ﬂame and disappears in a puff of smoke ——--—-——————+ 1 E9. A metal ring is faiiing along a wire with steady current ﬂowing upward. What direction is the induced current in the ring, as viewed from above? a) clockwise b) counter-clockwise c) there is no current induced in the ioop d) the ring bursts into ﬂame and disappears in a puff of smoke I 20. In Europe, the standard voltage avaiiable from a wall socket is 240V nns. What is the maximum voltage in this case? a) 240V i3) 120V c) 170V d) 340V Answers: i)B 2)C 3)i3 4)A 5)D 6)!) 7)C 8)A 9)C 10)A EDA 12)B 13)A l4)C E5)C 16)B 17)C 18)A l9)C 20)D ...
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