Physics II exam 2, Chapters 30-35
You make a telephone call from New York to a friend in London. Estimate how long it will take the electrical signal generated by your voice to reach London, assuming the signal is (a) carried on a telephone cable under the Atlantic Ocean, and (b) sent via satellite 36,000 km above the ocean. Would this cause a noticeable delay in either case?
(a) 0.017 s (b) 0.24 s
A 30-pF air-gap capacitor has circular plates of area A = 100 cm2 . It is charged by a 70-V battery through a 2.0-Ω resistor. At the instant the battery is connected, the electric field between the plates is changing most rapidly. At this instant, calculate (a) the current into the plates, and (b) the rate of change of electric field between the plates. (c) Determine the magnetic field induced between the plates. Assume E is uniform between the plates at any instant and is zero at all points beyond the edges of the plates.
(a) 35 A (b) 4.0 x 10^14V/m.s (c) 1.2 x 10^-4T.
The antenna of a cell phone is often ¼ wavelength long. A particular cell phone has an 8.5- cm-long straight rod for its antenna. Estimate the operating frequency of this phone.
880 MHz.
Find the magnetic energy stored in the air gap between two very large magnetic pole pieces, one North, one South, each with an area of 100 cm2. Assume the 0.05 T magnetic field is uniform within the 2-cm gap.
0.2J
A 10-mH inductor is connected in series with a 10-ohm resistor, a switch and a 6-volt battery. What is the time constant of the circuit? How long after the switch is closed will the current reach 99 percent of its final value?
1.0 ms, 4.6 ms
An RLC circuit has L = 250 mH, C = 0.200 μF, and R = 2.00 kΩ. What is the angular frequency of its damped oscillations?
2000 rad/s
The magnetic field in a superconducting solenoid is 3.0 T. How much energy per unit volume is stored in the solenoid, in J/m3? μ0 = 4π × 10−7 T ⋅ A/m
3.6 × 106 J/m3
If we wished to construct a "tank circuit" where electric charge originally stored on a capacitor flows through an inductor, then back again, what value of inductance should we place in series with a fully-charged 100 μF capacitor to get the circuit to resonate at 60.0 Hz?
70.4 mH
A laser beam is incident from the air at an angle of 30.00° to the vertical onto a solution of Karo syrup in water. If the beam is refracted to 19.24° to the vertical, what is the index of refraction of the syrup solution?
ANSWER: 1.517
The index of refraction for red light in water is 1.331 and for blue light is 1.340. If a ray of white light enters the water at an angle of incidence of 83.00°, what are the underwater angles of refraction for the blue and red components of the light?
ANSWER: 47.79° (blue), 48.22° (red)
The magnetic field amplitude in an electromagnetic wave in vacuum is related to the electric field amplitude by B =
a) E/c
A rod (length = 10 cm) moves on two horizontal frictionless conducting rails, as shown. The magnetic field in the region is directed perpendicularly to the plane of the rails and is uniform and constant. If a constant force of 0.60 N moves the bar at a constant velocity of 2.0 m/s, what is the current through the 12-Ω load resistor? a. 0.32 A b. 0.34 A c. 0.37 A d. 0.39 A e. 0.43 A
a)0.32 A
A coil is wrapped with 300 turns of wire on the perimeter of a square frame (side length = 20 cm). Each turn has the same area as the frame, and the total resistance of the coil is 1.5 Ω. A uniform magnetic field perpendicular to the plane of the coil changes in magnitude at a constant rate from 0.50 T to 0.90 T in 2.0 s. What is the magnitude of the induced emf in the coil while the field is changing? a. 2.4 V b. 1.6 V c. 3.2 V d. 4.0 V e. 8.4 V
a)2.4 V
A 400-turn circular coil (radius = 1.0 cm) is oriented with its plane perpendicular to a uniform magnetic field which has a magnitude that varies sinusoidally with a frequency of 90 Hz. If the maximum value of the induced emf in the coil is observed to be 4.2 V, what is the maximum value of the magnitude of the varying magnetic field? a. 59 mT b. 62 mT c. 65 mT d. 68 mT e. 31 mT
a)59 mT
A circular loop (area = 0.20 m 2 ) turns in a uniform magnetic field with B = 0.13 T. At an instant when the angle between the magnetic field and the normal to the plane of the loop is (π) rads and is decreasing at the rate of 0.50 rad/s, what is the magnitude of the emf induced in the loop? a. zero b. 13 mV c. 26 mV d. 20 mV e. 18 mV
a)zero
Two mirrors are at right angles to one another. If an object is placed near the mirrors, what is the largest number of images that would be seen in the mirrors? a. 3 b. 2 c. 4 d. 5 e. 6
a. 3
. Find the frequency of X-rays of wavelength 1 Å = 10^(-!0)m a. 3 × 10^(18) Hz b. 3 × 1010 MHz c. 6 × 109 Hz d. 3 × 108 Hz e. 3 × 1020 Hz
a. 3 × 1018 Hz
What is the inductance of a series RL circuit in which R = 1.0 KΩ if the current increases to one-third of its final value in 30 μs? a. 74 mH b. 99 mH c. 49 mH d. 62 mH e. none of the above
a. 74 mH
A layer of ethyl alcohol (n = 1.361) is on top of water (n = 1.333). To the nearest degree, at what angle relative to the normal to the interface of the two liquids is light totally reflected? a. 78° b. 88° c. 68° d. 49° e. the critical angle is undefined
a. 78°
Which of the following are the units of a henry and a farad respectively? a. J ⋅ s2/C2 and C2/J b. V ⋅ s/A and V/C c. V/(A ⋅ s) and C/V d. N ⋅ m/A2 and 1/J e. None of the above
a. J ⋅ s2/C2 and C2/J
Light behaves like a. a wave at times, and a particle at other times. b. a wave. c. a particle. d. both a wave and a particle, because of its dual nature
a. a wave at times, and a particle at other times.
A magician can make a candle look as if it is burning under water by focusing light from a candle flame burning in air directly on top of an underwater candle. To do this you want to use a (Hint: eliminate those that cannot work.) a. concave mirror farther than one focal length from the burning candle. b. a convex mirror farther than one focal length from the burning candle. c. a biconcave lens farther than one focal length from the burning candle. d. a concave mirror closer than one focal length to the burning candle. e. a convex lens closer than one focal length to the burning candle.
a. concave mirror farther than one focal length from the burning candle.
An object is placed 15 cm in front of a diverging lens whose focal length is 12 cm. Where will the image be located (in cm)? a. −6.7 b. −7.2 c. −0.15 d. −60 e. −5.0
a. −6.7
A plane parallel plate capacitor has plates of 10 cm2 area that are 1.0 mm apart. At an instant when charge is being accumulated on the plates at a rate of 12 nC/s, the displacement current between the plates is a. 1.06 × 10− 16 A. b. 1.2 × 10− 8 A. c. 8.85 × 10− 9 A. d. 1.00 A. e. 1.36 A.
b. 1.2 × 10− 8 A.
An electric field of 4.0 μV/m is induced at a point 2.0 cm from the axis of a long solenoid (radius = 3.0 cm, 800 turns/m). At what rate is the current in the solenoid changing at this instant? a. 0.50 A/s b. 0.40 A/s c. 0.60 A/s d. 0.70 A/s e. 0.27 A/s
b)0.40 A/s
A 20-cm length of wire is held along an east-west direction and moved horizontally to the north with a speed of 3.0 m/s in a region where the magnetic field of the earth is 60 μT directed 30° below the horizontal. What is the magnitude of the potential difference between the ends of the wire? a. 36 μV b. 18 μV c. 31 μV d. 24 μV e. 21 μV
b)18 μV
A conducting rod (length = 2.0 m) spins at a constant rate of 2.0 revolutions per second about an axis that is perpendicular to the rod and through its center. A uniform magnetic field (magnitude = 8.0 mT) is directed perpendicularly to the plane of rotation. What is the magnitude of the potential difference between the center of the rod and either of its ends? a. 16 mV b. 50 mV c. 8.0 mV d. 0.10 mV e. 100 mV
b)50 mV
At what frequency should a 200-turn, flat coil of cross-sectional area of 300 cm2 be rotated in a uniform 30-mT magnetic field to have a maximum value of the induced emf equal to 8.0 V? a. 7.5 Hz b. 7.1 Hz c. 8.0 Hz d. 8.4 Hz e. 16 Hz
b)7.1 Hz
A coil is wrapped with 300 turns of wire on the perimeter of a circular frame (radius = 8.0 cm). Each turn has the same area, equal to that of the frame. A uniform magnetic field is turned on perpendicular to the plane of the coil. This field changes at a constant rate from 20 to 80 mT in a time of 20 ms. What is the magnitude of the induced emf in the coil at the instant the magnetic field has a magnitude of 50 mT? a. 24 V b. 18 V c. 15 V d. 10 V e. 30 V
b-18 V
A light ray strikes a hexagonal ice crystal floating in the air at a 30° angle to one face, as shown below. The hexagonal faces of the crystal are perpendicular to the plane of the page. All the rays shown are in the plane of the page, and nice = 1.30. Which outgoing ray is the correct one?
b.
The wave front shown at the left for light in air reaches the plane surface (shown by a slanted line) that bounds a medium with n = 1.50. Which diagram below correctly shows the wave front while entering the medium at the right?
b.
A series LC circuit contains a 100 mH inductor, a 36.0 mF capacitor and a 12 V battery. The period of the electromagnetic oscillations in the circuit is a. 0.0227 s. b. 0.377 s. c. 2.26 s. d. 105 s. e. 1750 s.
b. 0.377 s.
An object 50-cm high is placed 1.0 m in front of a converging lens whose focal length is 1.5 m. Determine the image height (in cm). a. 77 b. 150 c. 52 d. 17 e. 83
b. 150
Two flat rectangular mirrors are set edge to edge and placed perpendicular to a flat nonreflecting surface. The edges of the two mirrors meet at a 30° angle. A light ray that enters parallel to mirror 2 reflects from mirror 1 and then from mirror 2. The angle of reflection of that ray from mirror 2 is a. 0°. b. 30°. c. 60°. d. 90°. e. 120°
b. 30°.
Before the switch is closed in the figure, the potential across the capacitor is 200 V. At some instant after the switch is closed, the instantaneous current is 0.70 A. What is the energy in the capacitor at this instant? a. 49 mJ b. 31 mJ c. 80 mJ d. 0.13 J e. 62 mJ
b. 31 mJ
A diver shines an underwater searchlight at the surface of a pond (n = 1.33). At what angle (relative to the surface) will the light be totally reflected? a. 47.3° b. 41.2° c. 51.1° d. 58.7° e. 49.8°
b. 41.2°
An object 20-cm high is placed 50.0 cm in front of a lens whose focal length is 5.00 cm. Where will the image be located (in cm)? a. 5.13 b. 5.56 c. 5.72 d. 5.93 e. 4.55
b. 5.56
Two mirrors are at right angles to one another. A light ray is incident on the first at an angle of 30° with respect to the normal to the surface. What is the angle of reflection from the second surface? a. 30° b. 60° c. 45° d. 53° e. 75°
b. 60°
A 10-cm focal length converging lens is used to magnify small newspaper print 2.0 mm high. Calculate the height of the image (in mm) for the maximum magnification for a normal eye. a. 3.5 b. 7.0 c. 9.2 d. 12 e. 2.5
b. 7.0
The actual depth of a shallow pool 1.00 m deep is not the same as the apparent depth seen when you look straight down at the pool from above. How deep (in cm) will it appear to be? (nwater = 1.33.) a. 133 b. 75.2 c. 90.6 d. 117 e. 100
b. 75.2
The image of an object beneath the surface of a medium of refractive index n > 1 is seen in air by a person looking down on the surface. This image, formed by light rays leaving the flat refractive surface, is a. real and closer to the viewer than the object. b. virtual and closer to the viewer than the object. c. real and farther from the viewer than the object. d. virtual and farther from the viewer than the object. e. virtual and the same distance from the viewer as the object.
b. virtual and closer to the viewer than the object.
Since e = 8.85e-12 C^(2)/Nm^2, the units of eE^2 can be reduced to
c) J/m^3
A metal blade spins at a constant rate of 5.0 revolutions per second about a pivot through one end of the blade. This rotation occurs in a region where the component of the earth's magnetic field perpendicular to the blade is 30 μT. If the blade is 60 cm in length, what is the magnitude of the potential difference between its ends? a. 0.24 mV b. 0.20 mV c. 0.17 mV d. 0.27 mV e. 0.34 mV
c)0.17 mV
A loop of wire (resistance = 2.0 mΩ) is positioned as shown with respect to a long wire which carries a current. If d = 1.0 cm, D = 6.0 cm, and L = 1.5 m, what current is induced in the loop at an instant when the current in the wire is increasing at a rate of 100 A/s? a. 34 mA b. 30 mA c. 27 mA d. 38 mA e. 0.50 mA
c)27 mA
A small airplane with a wingspan of 12 m flies horizontally and due north at a speed of 60 m/s in a region where the magnetic field of the earth is 60 μT directed 60° below the horizontal. What is the magnitude of the induced emf between the ends of the wing? a. 50 mV b. 31 mV c. 37 mV d. 44 mV e. 22 mV
c)37 mV
A square loop (length along one side = 20 cm) rotates in a constant magnetic field which has a magnitude of 2.0 T. At an instant when the angle between the field and the normal to the plane of the loop is equal to 20° and increasing at the rate of 10°/s, what is the magnitude of the induced emf in the loop? a. 13 mV b. 0.27 V c. 4.8 mV d. 14 mV e. 2.2 mV
c)4.8 mV
A long straight wire is parallel to one edge and is in the plane of a single-turn rectangular loop as shown. If the loop is changing width so that the distance x changes at a constant rate of 4.0 cm/s, what is the magnitude of the emf induced in the loop at an instant when x = 6.0 cm? Let a = 2.0 cm, b = 1.2 m, and I = 30 A. a. 5.3 μV b. 2.4 μV c. 4.8 μV d. 2.6 μV e. 1.3 μV
c)4.8 μV
In the arrangement shown, a conducting bar of negligible resistance slides along horizontal, parallel, frictionless conducting rails connected as shown to a 2.0-Ω resistor. A uniform 1.5-T magnetic field is perpendicular to the plane of the paper. If L = 60 cm, at what rate is thermal energy being generated in the resistor at the instant the speed of the bar is equal to 4.2 m/s? a. 8.6 W b. 7.8 W c. 7.1 W d. 9.3 W e. 1.8 W
c)7.1 W
The speed of light is given by the value of
c)sqrt(sig,u)^-1
A flat coil of wire consisting of 20 turns, each with an area of 50 cm2 , is positioned perpendicularly to a uniform magnetic field that increases its magnitude at a constant rate from 2.0 T to 6.0 T in 2.0 s. If the coil has a total resistance of 0.40 Ω, what is the magnitude of the induced current? a. 0.70 A b. 0.60 A c. 0.50 A d. 0.80 A e. 0.20 A
c-0.50 A
A light ray strikes a hexagonal ice crystal floating in the air perpendicular to one face, as shown below. The hexagonal faces of the crystal are perpendicular to the plane of the page. All the rays shown are in the plane of the page, and nice = 1.30. Which outgoing ray is correct when the incoming ray strikes the crystal face on the left head on?
c.
The figure shows an LR circuit with a switch and a 240-volt battery. At the instant the switch is closed the current in the circuit and the potential difference between points a and b, Vab, are a. 0 A, 0 V b. 0 A, −240 V c. 0 A, +240 V d. 0.024 A, 0 V e. 0.024 A, +240 V
c. 0 A, +240 V
When a switch is closed, completing an LR series circuit, the time needed for the current to reach one half its maximum value is ____ time constants. a. 0.250 b. 0.500 c. 0.693 d. 1.00 e. 1.44
c. 0.693
The speed of light changes when it goes from ethyl alcohol (n = 1.36) to carbon tetrachloride (n = 1.46). The ratio of the speed in carbon tetrachloride to the speed in ethyl alcohol, v2/v1, is a. 1.99 b. 1.07 c. 0.932 d. 0.511 e. 0.760
c. 0.932
The magnetic field of a plane-polarized electromagnetic wave moving in the z-direction is given by in SI units. What is the frequency of the wave? a. 500 MHz b. 250 kHz c. 1.25 MHz d. 10 mHz e. 300 MHz
c. 1.25 MHz
For the circuit shown, what is the rate of change of the current in the inductor when the current in the battery is 0.50 A? a.600 A/s b.400 A/s c.200 A/s d.800 A/s e.500 A/s
c. 200 A/s
An FM radio station broadcasts at 98.6 MHz. What is the wavelength of the radiowaves? a. 60.8 m b. 6.08 m c. 3.04 m d. 0.314 m e. 0.33 cm
c. 3.04 m
A circuit contains two inductors of 6.0 mH inductance in series placed in parallel with an inductor of 8.0 mH inductance. After one of the 6.0 mH inductors burns out, the repair person wants to replace all three inductors with one inductor of equivalent inductance. Assuming inductors combine in series and parallel the same way resistors do, what inductance should she use? a. 3.0 mH b. 3.4 mH c. 4.8 mH d. 11 mH e. 20 mH
c. 4.8 mH
A plane convex lens is made of glass (n = 1.5) with one flat surface and the other having a radius of 20 cm. What is the focal length (in cm) of the lens? a. 20 b. 30 c. 40 d. 10 e. 50
c. 40
A diver shines light up to the surface of a flat glass-bottomed boat at an angle of 30° relative to the normal. If the index of refraction of water and glass are 1.33 and 1.5, respectively, at what angle (in degrees) does the light leave the glass (relative to its normal)? a. 26 b. 35 c. 42 d. 22 e. 48
c. 42
A layer of water (n = 1.333) floats on carbon tetrachloride (n = 1.461) contained in an aquarium. To the nearest degree, what is the critical angle at the interface between the two liquids? a. 88° b. 78° c. 66° d. 58° e. 43°
c. 66°
21. Coil 1, connected to a 100 Ω resistor, sits inside coil 2. Coil 1 is connected to a source of 60 cycle per second AC current. Which statement about coil 2 is correct? a. No current will be induced in coil 2. b. DC current (current flow in only one direction) will be induced in coil 2. c. AC current (current flow in alternating directions) will be induced in coil 2. d. DC current will be induced in coil 2, but its direction will depend on the initial direction of flow of current in coil 1. e. Both AC and DC current will be induced in coil 2.
c. AC current (current flow in alternating directions) will be induced in coil 2
A metal rod of length L in a region of space where a constant magnetic field points into the page rotates clockwise about an axis through its center at constant angular velocity ω. While it rotates, the point(s) at lowest potential is(are)
c. C.
The correct form of Ampere's law for circuits with gaps in them is
d)
An AC generator consists of 6 turns of wire. Each turn has an area of 0.040 m 2 . The loop rotates in a uniform field (B = 0.20 T) at a constant frequency of 50 Hz. What is the maximum induced emf? a. 13 V b. 2.4 V c. 3.0 V d. 15 V e. 4.8 V
d)15 V
An induced emf is produced in a. a closed loop of wire when it remains at rest in a nonuniform static magnetic field. b. a closed loop of wire when it remains at rest in a uniform static magnetic field. c. a closed loop of wire moving at constant velocity in a nonuniform static magnetic field. d. all of the above. e. only (b) and (c) above.
c. a closed loop of wire moving at constant velocity in a nonuniform static magnetic field.
When light is either reflected or refracted, the quantity that does not change in either process is its a. direction of travel. b. dispersion. c. frequency. d. speed. e. wavelength.
c. frequency.
The difference between a DC and an AC generator is that a. the DC generator has one unbroken slip ring. b. the AC generator has one unbroken slip ring. c. the DC generator has one slip ring split in two halves. d. the AC generator has one slip ring split in two halves. e. the DC generator has two unbroken slip rings
c. the DC generator has one slip ring split in two halves.
A monochromatic (single frequency, single wavelength) light ray in air (n = 1) enters a glass prism (n = 1.5). In the glass prism a. both the frequency and the wavelength are the same as in air b. the frequency is the same, but the wavelength is greater than in air. c. the frequency is the same, but the wavelength is smaller than in air. d. the wavelength is the same, but the frequency is greater than in air. e. the wavelength is the same, but the frequency is smaller than in air.
c. the frequency is the same, but the wavelength is smaller than in air.
After a switch is thrown to remove the battery from a DC LR circuit, but the circuit is still left complete, the time constant represents a.the time rate of change of the current in the circuit. b.the time rate of change of the induced emf in the circuit. c.the magnitude of the ratio of the current to the time rate of change of the current. d.all of the above. e.only (a) and (b) above.
c.the magnitude of the ratio of the current to the time rate of change of the current.
A planar loop consisting of four turns of wire, each of which encloses 200 cm2 , is oriented perpendicularly to a magnetic field that increases uniformly in magnitude from 10 mT to 25 mT in a time of 5.0 ms. What is the resulting induced current in the coil if the resistance of the coil is 5.0 Ω? a. 60 mA b. 12 mA c. 0.24 mA d. 48 mA e. 6.0 mA
d)48 mA
The magnetic flux through a loop perpendicular to a uniform magnetic field will change a. if the loop is replaced by two loops, each of which has half of the area of the original loop. b. if the loop moves at constant velocity while remaining perpendicular to and within the uniform magnetic field. c. if the loop moves at constant velocity in a direction parallel to the axis of the loop while remaining in the uniform magnetic field. d. if the loop is rotated through 180 degrees about an axis through its center and in the plane of the loop. e. in none of the above cases.
d)if the loop is rotated through 180 degrees about an axis through its center and in the plane of the loop.
A circuit contains two inductors of 6.0 mH inductance in parallel placed in series with an inductor of 8.0 mH inductance. After one of the 6.0 mH inductors burns out, the repairman wants to replace all three inductors with one inductor of equivalent inductance. Assuming inductors combine in series and parallel the same way resistors do, what inductance should he use? a. 3.0 mH b. 3.4 mH c. 4.8 mH d. 11 mH e. 20 mH
d. 11 mH
A series LC circuit contains a 100 mH inductor, a 36.0 mF capacitor and a 12 V battery. The angular frequency of the electromagnetic oscillations in the circuit is a. 36.0 × 10−4 rad/s. b. 6.00 × 10−2 rad/s. c. 2.78 rad/s. d. 16.7 rad/s. e. 277 rad/s.
d. 16.7 rad/s.
The switch in the figure is closed at t = 0 when the current I is zero. When I = 15 mA, what is the potential difference across the inductor? a. 240 V b. 60 V c. 0 d. 180 V e. 190 V
d. 180 V
A series LC circuit contains a 100 mH inductor, a 36.0 mF capacitor and a 12 V battery. The frequency of the electromagnetic oscillations in the circuit is a. 5.73 × 10−4 Hz. b. 9.55 × 10−3 Hz. c. 0.442 Hz. d. 2.65 Hz. e. 44.0 Hz.
d. 2.65 Hz.
An aquarium contains a 5-cm layer of water (n = 1.33) floating on top of carbon tetrachloride (n = 1.461). If the angle of incidence into the water from the air is 30°, what is the angle of refraction into the carbon tetrachloride? a. 58° b. 69° c. 37° d. 20° e. 75°
d. 20°
The magnetic field of a plane-polarized electromagnetic wave moving in the z-direction is given by in SI units. What is the maximum E-field? a. 1000 V/m b. 180 V/m c. 81 V/m d. 360 V/m e. 0.40 V/m
d. 360 V/m
A light ray whose frequency is 6.00 × 1014 Hz in vacuum is incident on water (n = 1.33). The wavelength of the light after it enters the water is (in nm) a. 798 b. 500 c. 665 d. 376 e. 266
d. 376
A light ray is incident on the surface of water (n = 1.33) at an angle of 60° relative to the normal to the surface. The angle of the reflected wave is a. 80° b. 40° c. 20° d. 60° e. 30°
d. 60°
What should be the height of a dipole antenna (of dimensions 1/4 wavelength) if it is to transmit 1200 kHz radiowaves? a. 11.4 m b. 60 cm c. 1.12 m d. 62.5 m e. 250 m
d. 62.5 m
High frequency alternating current is passed through a solenoid that contains a solid copper core insulated from the coils of the solenoid. Which statement is correct? a. A copper core remains cool no matter what the frequency of the current in the solenoid is. b. The copper core remains cool because the induced emf is parallel to the solenoid axis and fluctuates rapidly. c. The copper core heats up because an emf parallel to the solenoid axis is induced in the core. d. The copper core heats up because circular currents around its axis are induced in the core. e. The copper core heats up because the electric field induced in the copper is parallel to the magnetic field produced by the solenoid.
d. The copper core heats up because circular currents around its axis are induced in the core.
A bar magnet is dropped from above and falls through the loop of wire shown below. The north pole of the bar magnet points downward towards the page as it falls. Which statement is correct? a. The current in the loop always flows in a clockwise direction. b. The current in the loop always flows in a counterclockwise direction. c. The current in the loop flows first in a clockwise, then in a counterclockwise direction. d. The current in the loop flows first in a counterclockwise, then in a clockwise direction. e. No current flows in the loop because both ends of the magnet move through the loop.
d. The current in the loop flows first in a counterclockwise, then in a clockwise direction
There is no current in the circuit shown in the figure below until the switch is closed. The current through the 20-Ω resistor the instant after the switch is closed is either [1] 15 A or [2] 5.0 A, and the current through the 20-Ω resistor after the switch has been closed a long time is either [3] 5.0 A or [4] 15 A. Which combination of the above choices is correct? a. [1] and [3] b. [1] and [4] c. [2] and [3] d. [2] and [4] e. None of these
d. [2] and [4]
A current may be induced in a coil by a. moving one end of a bar magnet through the coil. b. moving the coil toward one end of the bar magnet. c. holding the coil near a second coil while the electric current in the second coil is increasing. d. all of the above. e. none of the above.
d. all of the above.
At every instant the ratio of the magnitude of the electric to the magnetic field in an electromagnetic wave in vacuum is equal to a. the speed of radio waves. b. the speed of light. c. the speed of gamma rays. d. all of the above. e. only (a) and (b) above.
d. all of the above.
Magnetic fields are produced by a. constant electric currents. b. electric currents that vary sinusoidally with time. c. time-varying electric fields. d. all of the above. e. only (a) and (b) above.
d. all of the above.
If you stand closer to a concave mirror than a distance of one focal length, the image you see is a. real and inverted. b. real and upright. c. virtual and inverted. d. virtual and upright. e. none of the above because you do not get an image
d. virtual and upright.
When you stand in front of a convex mirror, the image you see is a. real and inverted. b. real and upright. c. virtual and inverted. d. virtual and upright. e. real and inverted if your distance from the mirror is greater than two focal lengths.
d. virtual and upright.
When a switch is closed to complete a DC series RL circuit, a.the electric field in the wires increases to a maximum value. b.the magnetic field outside the wires increases to a maximum value. c.the rate of change of the electric and magnetic fields is greatest at the instant when the switch is closed. d.all of the above are true. e.only (a) and (c) above are true.
d.all of the above are true.
An inductor produces a back emf in a DC series RL circuit when a switch connecting the battery to the circuit is closed. We can explain this by a. Lenz's Law b. ncreasing magnetic flux within the coils of the inductor. c.increasing current in the coils of the inductor. d.all of the above. e.only (a) and (c) above.
d.all of the above.
When a switch is closed, completing an LR series circuit, the time needed for the current to reach three-quarters its maximum value is ____ time constants. a. 0.500 b. 0.693 c. 0.725 d. 1.33 e. 1.39
e. 1.39
An open circuit consists of a 12 μF parallel plate capacitor charged to 200 V and a 10 Ω resistor. At the instant when a switch closes the circuit (with no battery in it) the displacement current between the plates of the capacitor is a. 1.2 μA. b. 2.4 × 10− 4 A. c. 2.4 mA. d. 10 A. e. 20 A.
e. 20 A.
. A metal rod of length L in a region of space where a constant magnetic field points into the page rotates clockwise about an axis through its center at constant angular velocity ω. While it rotates, the point(s) at highest potential is(are)
e. A and E.
In the atmosphere, the shortest wavelength electromagnetic waves are called a. microwaves. b. infrared waves. c. ultraviolet waves. d. X-rays. e. gamma rays.
e. gamma rays.
Light can exhibit the characteristics of a. a particle with energy E = hf. b. a wave with wavelength . c. a particle or wave that travels at speed in all materials. d. all of the above. e. only (a) or (b) above.
e. only (a) or (b) above.
When a light ray travels between any two points, the path it takes is the one that (Hint: Eliminate answers you know are wrong.) a. covers the greatest distance. b. follows the greatest index of refraction. c. avoids travel in more than one medium. d. is the mean between the longest and the shortest paths. e. takes the least time.
e. takes the least time.
Assume a 60-Hz EM wave is a sinusoidal wave propagating in the z direction with E pointing in the x direction, and Emax = 2.0 V/m. Write vector expressions for E and B as functions of position and time. Hint: First calculate wavelength, wavenumber, angular frequency and Bmax . Substitute these values in time varying E and B expressions.
gottta solve
A light ray is partially reflected and partially refracted at a boundary between two media, the upper one having index of refraction n, the lower one having index of refraction n', as shown in the figure. The reflected ray is perpendicular to the refracted ray when
n'=ntan(theta)
