PH 2004 Spring Tests

PH 2004 Spring Tests - Physics Honors Physics Honors...

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Unformatted text preview: Physics Honors Physics Honors Distributed By: Tyrone G Carter Form 1 Test: Chapters 23 and 24 DO NOT WRITE ON THIS TEST. SHOW WORK ON ANSWER SHEET. REPORT ALL ANSWERS TO 3 SIGNIFICANT FIGURES VECTOR ANSWERS MUST HAVE MAGNITUDE AND DIRECTION USE SCIENTIFIC NOTATION WHEN APPROPRIATE {X >100 or X < 0.1} v f n n1 sin 1 n2 sin 2 hi d i ho do 1 1 1 f d o di c = 3.00 x 108 m/s d sin m c v t 2m 1 2m 1 c 4 t 4nf A light wave travels from air into water, striking the boundary between the media at an angle = 40 to the normal, as shown at right. The speed of light in the air is c = 3.00 x 108 m/s, and the speed of light in water is v = 2.26 x 108 m/s. m mc 2 2nf air 1) In what direction does the refracted part of the light wave travel? ANSWER: [D29ºR] 2) If the light were traveling from the water toward the air, for what range of water incident angles will no transmission occur? ANSWER: 90º ≥ ≥ 48.9º You place a ball of radius 3 cm at a point along the principal axis 15 cm from a converging mirror. The virtual reflection of the ball appears to have a radius of 7 cm. 3) What is the focal length of the mirror? ANSWER: 26.3 cm An object is placed a distance d in front of a diverging lens of focal length f. 4) Draw a ray diagram that will show the location, size, and orientation of the image produced by the lens. ANSWER: See Figure 23-33, p. 663 White light strikes a thin film of oil at the surface of a puddle of water. Part of the film appears to be green when viewed by an observer. The index of refraction of oil is 1.20, the index of refraction of water is 1.50, and green light has wavelength = 525 nm in air. 5) What are two possible values for the thickness of the green part of the film? ANSWER: 263 nm, 525 nm, 788 nm, etc. Red light of wavelength = 650 nm passes through a diffraction grating whose slits are 1000 nm apart, and then strikes a screen 4 cm away, as shown at right. grating screen 6) How wide is the central bright spot on the screen? ANSWER: 2.60 cm The visible color spectrum can be produced in various ways, from thin films to rainbows. 7) a) b) c) Explain how diffraction can create a spectrum. ANSWER: see p. 690 Explain how refraction can create a spectrum. ANSWER: see p. 686 Describe how the diffraction spectrum differs from the refraction spectrum. A converging lens, labeled #1, has a focal length 6 cm. A 2-cm tall candle is placed with its base a distance x from the center of lens, along the principal axis. An identical lens, labeled #2, is placed 23 cm behind the first lens, as shown. 8) 9) You hold a vertical piece of paper between the lenses so that a sharp image of the candle is formed. candle lens #1 lens #2 If distance x = 13 cm, how far is the paper from lens #1? ANSWER: 11.1 cm You now hold the paper 11 cm to the right of lens #2 and then move the candle so that a sharp image is formed. What is distance x when the image is in focus? ANSWER: 15.5 cm Distributed By: Tyrone G Carter x 23 cm TGC Physics Honors Physics Honors F Distributed By: Tyrone G Carter Test: Chapter 16 DO NOT WRITE ON THIS TEST. SHOW WORK ON ANSWER SHEET REPORT ALL ANSWERS TO 3 SIGNIFICANT FIGURES VECTOR ANSWERS MUST HAVE MAGNITUDE AND DIRECTION USE SCIENTIFIC NOTATION WHEN APPROPRIATE {X >100 or X < 0.1} kqQ r2 E F kQ q r2 Form 1 sin tan k 8.99 10 9 N m2 C 2 (sometimes) Four point charges of magnitude 1.0 C are located at the corners of a square that is 2.0 m on a side. The charge in the upper right corner is positive, and the other three are negative. 1) What is the net force acting on the positive point charge? ANSWER: 4.30 x 10-3 N [L45ºD] 2) What is the electric field at the center of the square? ANSWER: 8.98 x 103 N/C [L45ºD] A solid gold brick is resting on an insulating surface. The brick is given a net negative charge. 3) Explain why there is no electric field inside the brick. Pendulum bob C and rod B are in contact with each other and made from conducting material. Rod B is fixed in place, and C is suspended from a wire and free to swing. Rod A is a positively charged conductor that is initially very far away from B. ANSWER: See p. 470 A ++++++++++ C B 4) Briefly describe what happens as A slowly moves to the right until it touches B. ANSWER: Before A touches B, positive charge moves to the right in A; B becomes negatively charged; and C becomes positively charged. When A touches B, all three are positively charged, and C swings to the right. A point charge q = 1 C is located at the origin of a coordinate system. A second point charge Q = 3 C is located at x = 2.0 m. 5) 6) What is the x-coordinate of the point at which the net electric field is equal to zero? ANSWER: x = 0.73 m In the work space on your answer sheet, draw an xycoordinate system. Now sketch the graph of the electric field vs. position (E vs. x) on the interval –2 m ANSWER: < x < 4 m. The graph should be positive where the electric field points to the right. Two volleyballs, each of mass 0.3 kg, are identically positively charged by an electrostatic generator. Each is attached to an identical string and suspended from the same point. They repel each other and hang with separation 0.5 m. The length of the string from the point of support to the center of a ball is 3.0 m. 7) 8) 9) 3.0 m 3.0 m 0.5 m Draw the electric field lines for this arrangement in the work space on your answer sheet. ANSWER: see Fig. 16-25 (b) on p. 469 What is the charge on each ball? ANSWER: 2.61 x 10-6 C If the charge on one of the volleyballs was doubled, and the charge on the other was tripled, the balls would move farther apart. What then would be the separation distance between the balls at equilibrium? (Note: you do NOT need to use your answer to #8 to solve this problem) ANSWER: 0.909 m Distributed By: Tyrone G Carter TGC Physics Honors Physics Honors Distributed By: Tyrone G Carter Form 1 Test: Chapter 17 DO NOT WRITE ON THIS TEST. SHOW WORK ON ANSWER SHEET REPORT ALL ANSWERS TO 3 SIGNIFICANT FIGURES VECTOR ANSWERS MUST HAVE MAGNITUDE AND DIRECTION USE SCIENTIFIC NOTATION WHEN APPROPRIATE {X >100 or X < 0.1} kQ r o A C d V K 1 2 mv 2 U qV U= 1 qV 2 Vtotal Vi q CV V Ed 1 U = CV 2 2 o 8.85 1012 U= C2 N m2 q2 2C k 8.99×109 N m2 C2 Three point charges, each with charge q = +2.0 x 10-6 C, are located at the corners of an equilateral triangle with side length 2.0 m, as shown at right. 1) 2) 3) Using the work space on your answer sheet, draw the electric field lines and the equipotential lines surrounding this charge arrangement. ANSWER: see Fig. 17-3 on p. 484 Determine the electric potential at the center of the triangle. ANSWER: 4.67 x 104 V How much total work was done in moving these three charges from infinity to their present positions? ANSWER: 5.39 x 10-2 J At a certain point in space, the electric field E equals zero. 4) Must the absolute electric potential V also equal zero at that point? Give an example to explain your answer. ANSWER: If E = 0 then V = constant, but that constant does not need to be zero A certain capacitor has a capacitance of 2.0 x 10-9 F. Air is between its 0.68 m2 parallel plates, it is connected to a 9.0 V battery, and is fully charged. ANSWER: 3.09 x 10-3 m 5) How far apart are the plates of the capacitor? 6) With the battery still connected, the space between the plates is filled with ethanol ( = 25). How much additional charge leaves the battery because of the presence of the dielectric? ANSWER: 4.32 x 10-7 C 7) The ethanol is removed, and then later the battery is disconnected. The capacitor plates are then pulled apart so that the final plate separation is twice the initial plate separation. How much work did this require? ANSWER: 1.66 x 10 -7 J A negative charge moves in the direction of a uniform electric field. 8) a) b) Does the potential energy of the charge increase or decrease? Explain your answer. Does the electric potential increase or decrease? Explain your answer. An object of charge q1 = 2.0 mC and mass m1 = 2 kg is placed at the origin of a coordinate system, and another object of charge q2 = 3.0 mC and mass m2 = 3 kg is placed at x = 3.0 m. The two objects are simultaneously released from rest. 9) What is the speed of mass m2 at the instant mass m1 is located at x = -3.0 m? Distributed By: Tyrone G Carter ANSWER: Increase ANSWER: Decrease y m1, q1 m2, q2 x ANSWER: 54.7 m/s TGC Physics Honors Distributed By: Tyrone G Carter Physics Honors i q t irms imax 2 R Ri Test: Chapters 18 and 19 Form DO NOT WRITE ON THIS TEST. SHOW WORK ON ANSWER SHEET REPORT ALL ANSWERS TO 3 SIGNIFICANT FIGURES USE SCIENTIFIC NOTATION WHEN APPROPRIATE {X >100 or X < 0.1} L o 1 T R A V Vrms max P iV 2 1 1 C Ci R Ri q C 1 et RC q qo et RC i e 1 V iR P i2 R V2 R 1 1 C Ci i t RC R qo t RC e RC Household electricity uses a sinusoidal alternating current whose maximum voltage is 174 V. A light bulb that uses energy at an average rate of 100 W is plugged into an outlet in your home and turned on. 1) What is the resistance of the light bulb? ANSWER: 151 The circuit at right is made up of a 10-V battery, a 40- lightbulb, switch S, and four identical capacitors. A total charge of 1.5 C leaves the battery before the current stops. 2) What is the capacitance of each capacitor? ANSWER: 0.112 F 3) What is the current through the light bulb 3.0 seconds after the switch is closed? ANSWER: 0.152 A S A The circuit at right is made up of a 10-V battery and five identical light bulbs. A current of 0.50 A flows from the battery. 4) 5) What is the resistance of each light bulb? ANSWER: 11.4 What is the voltage between points A and B? ANSWER: 4.29 V B The circuit at right is made up of resistors R1 = 5 , R2 = 10 , R3 = 15 , R4 = 20 and R5 = 25 and ideal batteries 1 = 20 V and 2 = 25 V. 6) 7) What is the magnitude and direction of the current through resistor R3? ANSWER: 0.747 A [Down] Identify three possible specific physical differences between resistors R1 and R2. Explain why these physical differences affect the resistance. R1 R2 R3 1 R4 2 R5 ANSWER: R2 is longer, thinner, and/or made from a higher resistivity material. An electric nose hair trimmer operates until its battery “runs out”. 8) BRIEFLY explain how and why the following quantities change as the battery “dies”: a) internal resistance b) terminal voltage c) emf ANSWER: increases ANSWER: decreases ANSWER: remains constant An electric generating station produces 2.5 A of current at 500 V. The current travels through a 500-km long copper wire that has a resistivity of 1.68 x 10-8 ·m and a cross-sectional area of 0.001 m2. 9) What percentage of the energy produced by the generating station reaches the end of the wire? Distributed By: Tyrone G Carter ANSWER: 95.8% TGC Physics Honors Physics Honors i B o 2 r F Bi sin Distributed By: Tyrone G Carter Test: Chapter 20 and Chapter 22, Section 2 Ni A E BP oienclosed B o B o o 2 r t T m F qvB sin U qV o 4 107 A 1 Form F ma K mv r 2 1 2 mv 2 A 10-meter-long wire carries a current of 2.5 A toward the west in a region in which the magnetic field due to the earth points directly north. 1) What is the magnetic field due to the wire only at a point 5 cm directly above the wire? ANSWER: 1.00 x 10-5 T [North] -4 2) If the strength of the earth’s magnetic field is 5.0 x 10 T, what magnetic force acts on the wire? ANSWER: 1.25 x 10-2 N [Down] A 0.5 T magnetic field is produced by a large, ideal, air-core solenoid that is 25 m long, has a radius of 7.5 m, and is made up of 1.0 x 106 loops of wire. 3) What current flows through the solenoid? ANSWER: 9.95 A 4) Use Ampere’s Law to explain why the solenoid produces no magnetic field outside of its coils. ANSWER: If the Amperian Loop encircles the entire solenoid, no net current will be enclosed, so there will be no net magnetic field produced along the Loop. A proton of charge q = 1.60 x 10-19 C travels at 2.0 x 106 m/s [E45ºU] through a uniform 2.60 x 10-3 T magnetic field, experiencing a force of 6.0 x 10-16 N [S]. 5) What is the angle between the magnetic field and the proton’s direction of motion? ANSWER: 46.1º Charged particles passing through a bubble chamber leave tracks consisting of small hydrogen gas bubbles. These bubbles make visible the particles’ trajectories. In the following figure, the magnetic field is directed into the page, and the tracks are in the plane of the page, in the directions indicated by the arrows. Answer the following, and BRIEFLY explain your reasoning. 6) (a) (b) Which of the tracks correspond to negatively charged particles? ANSWER: C and D If all three particles have the same mass and have charges of equal magnitude, which is obviously changing its speed? ANSWER: C Two very long wires both carry current toward the west. One is directly above the other, and they are 2.0 m apart. The top wire carries a current of 1.5 A, and the bottom carries a current of 0.5 A. 7) What is the magnetic field halfway between the wires? ANSWER: 2.00 x 10-7 T [South] A single proton in an experiment is located at the origin of a coordinate system at time t = 0. At time t = 5 s, the proton begins to move to the right. At time t = 10 s, it stops at x = 5 m. It remains motionless until time t = 15 s, when the experiment ends. A magnetic field sensor is located at point P at coordinates (x,y) = (10 m, 5 m). 8) When and why is a magnetic field detected at point P? ANSWER: When the proton is in motion. An object of mass m and charge q is accelerated through a voltage V and into a magnetic field B. The magnetic field is perpendicular to the velocity of the object. 9) What is the radius of the object’s circular path in the magnetic field in terms of m, q, V, and B? ANSWER: r Distributed By: Tyrone G Carter 2mV qB 2 TGC Physics Honors Distributed By: Tyrone G Carter Physics Honors o 4 107 T m A 2 M i1 t i io etR L Test: Chapter 21 B N t B BA sin F Bi sin L ti Form 1 M it2 V iR P iV V constant N i 1 e R tR L XR R XC 1 C XR L x x x x x x A 1.0 kg cart carries a wire loop at an initial speed of 10 m/s to the right as it enters a 2.5 T magnetic field pointing into the plane of the page, as shown at right. The magnetic field is 1.0 m wide. The cart and loop are 30 cm wide. The loop is 20 cm tall and has a resistance of 1.5 . 1) What is the magnitude and direction of the current in the front wire just as it enters the magnetic field? ANSWER: 3.33 A [upwards] x x x x x x x x x x x x x x x x x x x x x x x x 2) What is the magnitude and direction of the force on the front wire just as it enters the magnetic field? ANSWER: 1.67 N [left] 3) What is the magnetic flux through the loop when it is completely inside the magnetic field? ANSWER: 0.150 T·m2 A The circuit at right consists of a 2.0 resistor, a switch, a 4.0 H inductor, and a 10 V ideal battery. The switch is connected to point A at time t = 0 B and stays closed for 2.5 s. At that time, the switch is instantaneously connected to point B. 4) 5) At what rate is the current through the resistor changing at t = 0, just after the switch is connected to point A? ANSWER: 2.50 A/s At what time t does the current decrease to 0.5 A? ANSWER: 6.43 s A bar magnet is initially located inside a coil of wire, as shown at right. The magnet is pulled to the left, out of the coil. 6) coil If you are looking to the right, into the coil, in what direction does current seem to flow as the magnet moves? Explain your answer. ANSWER: counterclockwise N S Consider two simple circuits. The first is made up of an AC voltage source and a capacitor. The second is made up of an identical AC voltage source and an inductor. 7) a) Explain why the impedance of the capacitor circuit is inversely proportional to frequency of the source. ANSWER: see p. 610 b) Explain why the impedance of the inductor circuit is directly proportional to frequency of the source. ANSWER: see p. 611 An input voltage Vrms = 120 V is applied to a transformer that has 500 primary turns and 2500 secondary turns. 8) What is the output rms-voltage of the transformer? ANSWER: 600 V Two solenoids are magnetically linked, as shown at right. The primary solenoid has self-inductance L1 = 5.0 H and is connected to a 3 resistor and a battery. The secondary solenoid has selfinductance L2 = 10.0 H and is connected to a 2 resistor. At one instant in time, the primary current has a value i1 = 3.0 A that is changing at 1.5 A/s. At that same instant, the secondary current has a value i2 = 1.0 A that is changing at 0.2 A/s. 9) What is the voltage of the battery? Distributed By: Tyrone G Carter L1 L2 R ANSWER: 17.4 V (M = 4.67 H) TGC R 1 Physics Honors Physics Honors R 8.315 Distributed By: Tyrone G 1 Test: Heat and Thermodynamics Form Carter Chapter 13-15 J mol K k 1.38 1023 J K N A 6.02 1023 molecules mole 3 K avg kT 2 V Vo T PV nRT PV NkT 3 NkT 2 ΔQ ΔT hA Δt Δx 3 U nRT 2 Q mcΔT ΔQ e A T14 T24 Δt T ec 1 L TH ΔU Q W 3kT m ΔQ ΔT kA Δt Δx Q ΔS Tavg Q ml W Pavg ΔV U QH W QL Properties of liquid water: coefficient of Density volume expansion 0.001 kg/cm3 2.10 x 10-4 K-1 vrms isobaric process CP QL W CPc W m2 K 4 5.67 108 TL TH TL e Molecular mass Specific Heat 4.186 kJ/kg·K Heat of vaporization 2260 kJ/kg Heat of fusion 18 g/mol W QH 333 kJ/kg A glass container is completely full and contains 300 cm3 of water initially at 370 K. The water is cooled by placing the container in an ice water bath at 273 K. The coefficient of volume expansion for water is 2.10 x 10 -4 K-1. The container is removed from the ice water bath when the hot water temperature has dropped to 290 K. Ignore any thermal effects on the glass container. 1. What additional volume of water can now be added to the container? ANSWER: 5.04 cm3 2. If there is initially 1.0 kg of ice in the water bath, how much ice remains at the end? ANSWER: 0.698 kg 3. What is the net entropy change for this process? ANSWER: 63.0 J/K A hollow spherical container holding a hot radioactive metal has 0.02 m thick walls and an outer surface area of 0.55 m2. The sphere is in an empty room whose walls are maintained at 273 K, as shown at right. At one instant in time, the temperature of the inner wall of the container is 320.1 K, the temperature of the outer wall of the container is 320.0 K, and heat is being radiated from the container to the walls of the room at a rate of 20 W. room wall temperature = 273 K outer wall temperature = 320.0 K inner wall temperature = 320.1 K wall thickness = 0.02 m 4. What is the emissivity of the metal sphere? ANSWER: e = 0.130 hot metal 5. What is the thermal conductivity of the metal? ANSWER: k = 7.27 W/m·K A 0.3 moles of steam undergoes the cycle shown in the PV diagram at right. The steam is at an initial pressure of 2.2 x 105 N/m2 when it expands in process #1 from 6.8 x 10-3 m3 to 9.9 x 10-3 m3, moving a piston upward. The steam is then depressurized in process #2 to 1.5 x 105 N/m2. The cycle is completed as the piston moves back and the steam returns to its initial pressure and volume in process #3. 6. What is the temperature at the end of process #1? ANSWER: 8.73 X 102 K 7. How much heat enters the gas, and during which process or processes does this occur? ANSWER: 1.70 kJ, during process #1 8. What is the efficiency of the cycle? ANSWER: 6.40% The ideal gas law is a useful approximation of the behavior of most gases. 9. a) b) P 1 2 3 V What assumptions are made about a gas being analyzed by the ideal gas law? What is an “ideal” gas? ANSWER: Elastic collisions, no vibrational or rotational kinetic energy, no intermolecular forces, etc. Describe and explain the error in a state variable calculated using the ideal gas law. How is the “real” answer different than the “ideal” answer? Why is there a difference? ANSWER: Translational kinetic energy (and thus impact speed with the wall, and thus pressure) are overestimated by the ideal gas law…pressure is lower. Distributed By: Tyrone G Carter TGC ...
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This note was uploaded on 08/29/2010 for the course PHYS 38234 taught by Professor Ramesh during the Spring '09 term at Berkeley.

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