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Physics 142 Exam 2
Multiple Choice from old exams
54
Physics
03/24/2013

Term
 Two wires are parallel to each other and carry the same current in the same direction i) there is no force between the wires ii) both wires are attracted to each other iii) both wires are repelled by each other iv) one wire is attracted and the other wire is repelled
Definition
 ii) both wires are attracted to each other
Term
 At a given instant, electromagnetic waves are traveling vertically up. The E-vector is oriented toward the south and horizontal. The direction of the B-vector at this instant is to the i) north ii) south iii) west iv) east
Definition
 iv) east
Term
 The distance of the image of an object in a plane mirror, to the mirror i) may be larger than the distance of the object to the mirror ii) may be smaller than the distance of the object to the mirror iii) is always equal to the distance of the object to the mirror iv) one cannot decide without knowing whether the image is real or virtual.
Definition
 iii) is always equal to the distance of the object to the mirror di=do
Term
 The plane of a rectangular loop is parallel to the magnetic field. The magnitude of the magnetic field is decreasing. i) there is no induced current on the loop ii) the induced current in the loop flows counter-clockwise iii) the induced current in the loop flows clockwise. iv) the direction of the induced current cannot be determined.
Definition
 i) there is no induced current in the loop   Φ=BA cos 90 Φ=O Tm2
Term
 The electric field vector of an electromagnetic wave is expressed as (in the metric system of units: Ē=2.0ÿcos(ωt+kz) i) the electric field vector is oscillating the in the ± z-direction ii) the magnetic field vector is oscillating in the ± y-direction iii) the electromagnetic waves are traveling the the + z-direction iv) the electromagnetic waves are traveling in the - z-direction
Definition
 iv) the electromagnetic waves are traveling in the - z-direction
Term
 Your cell phone uses a 3.6 volt battery. It can be recharged using a DC-power supply that can be plugged into the electric outlet at the wall (120 volts.) The transformer inside the recharger i) has more turns in its primary than its secondary ii) has less turns in its primary than its secondary iii) has the same number of turns in its primary as its secondary iv) no statement can be made concering the number of turns in the primary or the secondary
Definition
 i) has more turns in its primary than its secondary   Vs = Ns    3.6 Np=120 Ns Vp   Np                                 3.6    = Ns       120       Np
Term
 A beam made of a mixture of molecular hydrogen ions (H2+, molecular mass = 2amu) and doubly ionized Helium ions (He++, atomic mass = 4amu) enters a magnetic mass spectrometer as the same speed. The radius of the semi-circular trajectory for He++ ions is R. The radius of the semi-circular trajectory of the H2+ ions is r. (Of course, the radius is related to other quantities by applying Newton's second law to the magnetic force.) In this situation we can assert that i) R=r ii) R>r iii) R
Definition
 i) R=r   H2+       He++      F=ma=mv2= qvBsinθ    r             R                         r                   2amu        4amu            mV=qB                q=e        q=2e              r                       r=2v/eB     R=4V/23B          r=mv                   re=v        2eR=v              qb               2   B           4    B                                   re = 2eR         r=R   2       4
Term
 At a given instant, electromagnetic waves are traveling vertically down. The E-vector is oriented toward the east and horizontal. The direction of the B-vector at this instant is horizontal and points to the i) north ii) south iii) west iv) east
Definition
 ii) south
Term
 the image of an object in a plane mirror i) is always virtual ii) is always real iii) may be real or virtual depending on its position iv) may be real or virtual depending on its direction (up or down)
Definition
 i) is always virtual
Term
 At a power plant a transformer increases the line voltage from 200 Volts to 100,000 Volts. This transformer i) has more turns in its primary than its secondary ii) has less turns in its primary than its secondary iii) has the same number of turns in its primary as its secondary iv) No statement can be made concerning the number of turns in the primary or the secondary
Definition
 ii) has less turns in its primary than its secondary   200=primary     100,000=secondary Vs = Ns Vp  Np 100,000 = Ns     200       Np Ns=1,000 Np=2
Term
 For a right handed coordinate reference system xyz, the electric field vector of an electromagnetic wave is expressed as (in the metric system of units): Ē=2.0ȳ(ωt-kz) i) the electric field vector is oscillating in the ±x direction ii) the magnetic field vector is oscillating in the ±x direction iii) the magnetic field vector is oscillating in the ±y direction iv) the electromagnetic waves are traveling in the -z direction
Definition
 ii) the magnetic field vector is oscillating in the ±x direction   +2 prop +yE ±xB
Term
 A ray passes through the focal point of a concave mirror and hits the mirror. Which of the following statement is valid for the reflected ray? i) the reflected ray passes throguh the center of curvature ii) the reflected ray is parallel to the principle axis iii) the relected ray passes through the focal point iv) the reflected ray is normal to the surface of the mirror
Definition
 ii) the reflected ray is parallel to the principle axis
Term
 At a given instant, electromagnetic waves are traveling vertically down. The B-vector is oriented toward the north and horizontal. The direction of the E-vector at this instant is horizontal and points to the i) north ii) south iii) west iv) east
Definition
Term
 The image of an object from a concave mirror i) is always virtual ii) is always real iii) may be real or virtual depending on its position iv) is always upright
Definition
 iii) may be real or virtual depeding on its position   -convex is always virtual -concave is real or virtual
Term
 For a right handed coordinate reference system xyz, the magnetic field vector of an electromagnetic wave is expressed as (in the metric system of units): B=2.0ȳcos(ωt-kz). This equation implies that i) the electromagnetic waves are traveling in the +y direction ii) the electromagnetic waves are traveling in the +x direction iii) the magnetic field vector is oscillating in the ±x direction iv) the electric field vector is oscillating in the ±x direction
Definition
 iv) the electric field vector is oscillating in the ± x direction   B=±y prop= -z   E perp B
Term
 At a power plant a transformer increases the line voltage from 200 volts to 100,000 volts. This transformer i) the current in its primary is larger than the current in its secondary. ii) the current in its primary is smaller than the current in its secondary. iii) the current in its primary is the same as the current in its secondary. iv) no statement can be made concering the currents in the primary or the secondary.
Definition
 i) the current in its primary is larger than the current in its secondary.   P=200 S=100,000 P/S
Term
 Two wires are perpendicular to each other and carry the same current. Point P is closer to the horizontal wire. The direction of the total magnetic field at P is i) into the paper ii) out of the paper iii) parallel to the horizontal wire iv) parallel to the vertical wire
Definition
 ii) out of the paper
Term
 There is a current flowing in the single loop and the magnet is stationary. The ring as shown in the figure is repelled by the magnet but is clamped to its position. As you look into the North pole of the magnet, i) the current in the loop is flowing clockwise ii) the current in the loop is flowing counterclockwise iii) the direction of the current in the ring is determined by the direction of the induced current iv) the direction of the current cannot be determined if the magnet is not moving
Definition
 i) the current in the loop is flowing clockwise
Term
 A step-down transformer reduces the input voltage. In this case i) the number of turns in the primary is less than the number of turns in the secondary ii) the number of turns in the primary is larger in the number of turns in the secondary iii) the number of turns in the primary is the same as the number of turns in the secondary iv) no statement can be made about the relation between the number of the turns in the primary and the secondary
Definition
 ii) the number of turns in the primary is larger than the number of turns in the secondary Vp=Np  1° ↑V Vs  Ns           2° ↓V
Term
 An object is placed in front of a concave spherical mirror as shown. The three rays 1, 2, and 3, leave the top of the object and, after reflection, converge at a point on the top of the image. Ray 1 is parallel to the principal axis, ray 2 passes through F, and ray 3 passes through C. Which ray(s) will reflect back parallel to the principal axis? i) 1 only ii) 2 only iii) 3 only iv) 1, 2, and 3
Definition
 ii) 2 only
Term
 As a bean of monochromatic red light from a laser is transmitted from air into water i) both its speed and frequency changes ii) both its wavelength and speed changes iii) both its wavelength and frequency changes. iv) since the light is monochromatic, nothing changes
Definition
 ii) both its wavelength and speed changes
Term
 A converging lens of 25 cm of focal length is glued to a diverging lens of 10 cm of focal length without any air gap between the lenses i) the combined sytstem forms a diverging lens ii) the combined system forms a converging lens iii) one needs to know the indices of refractions to decide iv) one needs to know indices of refractions and the radii of curvatures of the lenses to decide
Definition
 i) the combined systems forms a diverging lens   1/f= 1/25-1/10 f=-16.67
Term
 Two wires are parallel to each other and carry the same current in the same direction i) there is no force between the wires ii) both wires are attracted to each other iii) both wires are repelled by each other iv) one wire is attracted and the other wire is repelled
Definition
 i) there is no force between the wires
Term
 a long, straight wire is in the same plane as a rectangular, conducting loop. The wire carries a constant current I as shown in the figure. Which one of the following statements is true if the wire is suddenly moved toward the loop? i) there will be no induced emf and no induced current ii) there will be an induced emf, but no induced current iii) there will be an induced current that is clockwise around the loop iv) there will be an induced current that is counterclockwise around the loop
Definition
 iv) there will be an induced current that is counterclockwise around the loop
Term
 Complete the following sentence: The various colors of visible light differ in i) frequency ii) frequency and wavelength iii) wavelength only iv) their speeds in a vacuum
Definition
 ii) frequency and wavelength
Term
 Which one of the following phrases most accurately describes paraxial rays? i) rays that pass throught the principal focus ii) rays that come to a focus on the principal axis iii) rays close to the principal axis and parallel to it iv) rays close to the principal axis, but not necessarily parallel to it
Definition
 iv) rays close to the principal axis, but not necessarily parralel to it
Term
 An object is placed in front of a concave spherical mirror as shown. The three rays 1, 2, and 3, leave the top of the object and, after reflection, converge at a point on the top of the image. Ray 1 is parallel to the principal axis, ray 2 passes through F, and ray 3 passes through C. Which ray(s) will reflect back on itself (themselves)? i) 1 only ii) 2 only iii) 3 only iv) 1,2, and 3
Definition
 iii) 3 only
Term
 A physics student desires to create a beam of light that consists of parallel rays. Which one of the following arrangements would allow her to accomplish this task? i) a point light source placed at the focal point of a convex mirror ii) a point light source placed at the focal point of a converging lens iii) a point light source placed at the focal length of a diverging lens iv) none of the above
Definition
 ii) a point light source placed at the focal point of a converging lens
Term
 A convergent lens of 5 cm of focal length is glued to a divergent lens of 10 cm of focal length without any air gap between the lenses. The focal length of the combined system is: i) 15 cm ii) 5 cm iii) 3.33 cm iv) 10 cm
Definition
 iv) 10 cm
Term
 For a right handed xyz coordinate system the instantaneous E-vector is in the -y direction, and direction of propagation of the electromagnetic waves is in the +z direction. In the case, the direction of the instantaneous B-vector is in i) +x direction ii) -x direction iii) +z direction iv) -z direction
Definition
 i) +x direction
Term
 The net magnetic field at some point of space is constant and points horizontally in the North direction. the current in a wire flows at this point in a horizontal direction from west towards the east. In that case, the direction of the magnetic force exerted on the wire is i) horizontal and pointing south ii) horizontal and pointing north iii) vertical and pointing down iv) vertical and pointing up
Definition
 iii) vertical and pointing down
Term
 A convergent lens with a very small focal length is place in contact (no gap) with a very large focal length convergent lens. The combined focal length is, i) much larger than either ii) approximately equal to the smaller iii) approximately equal to the larger iv) none of these
Definition
 ii) approximately equal to the smaller
Term
 An infinitely long wire and a single loop are on top of a table. The plane of the loop is parallel to the plane of the table. The loop is moving with constant speed v parallel to the wire. i) there will be no induced current in the loop ii) as seen from above, the induced current is running clockwise iii) as seen from above, the induced current is running counterclockwise iv) none of the above, we need to know the direction of the current in the wire
Definition
 i) there will be no induced current in the loop
Term
 An electron moving in the positive y direction, at right angles to a magnetic field, expereinces a magnetic force in the negative x direction. What is the direction of the magnetic field? i) it is in the negative x direction ii) it is in the positive y direction iii) it is in the negative z direction iv) it is in the positive z direction
Definition
 iv) it is in the positive z direction
Term
 For a right handed xyz coordinate system, if the E-vector is in the +z direction, and the B-vector is in the +x direction, what is the direction of propagation of the electromagnetic waves? i)+x ii)-x iii)+y iv)+z
Definition
 iii)+y
Term
 At a quiet pond with crystal clear water, you decide to fish with bow and arrow. When you aim at the fish you see, you must aim i) closer to the surface then you perceive the fish to be ii) directly at the fish iii) deeper than you perceive the fish to be iv) it depends on how deep the pond is
Definition
 iii) deeper than you perceive the fish to be
Term
 which of the following sets of characteristics descrives the image formed by a plane mirror? i) real and inverted ii) real and upright iii) virtual and upright iv) virtual and inverted
Definition
 iii) virtual and upright
Term
 The net magnetic field at some point of space is constant and points horizontally in the West direction. The current in a wire flows at this point in a horizontal direction from south toward the north. in that case, the direction of the magnetic force exerted on the wire is i) horizontal and pointing east ii) horizontal and pointing west iii) vertical and pointing down iv) vertical and pointing up
Definition
 iv) vertical and pointing up
Term
 As a vertical bar moves horizontally on two rails in a constant magnetic field, we observe that the voltage at point A is higher than the voltage at point B. We conclude that the direction of the constant magnetic field is i) in the plane of the paper, towards the right ii) in the plane of the paper, towards the left iii) perpendicular to the plane of the paper and into it iv) perpendicular to the plane of the paper and out of it
Definition
 iv) perpendicular to the plan of the paper and out of it
Term
 A point light-source emits light isotropically (the same in all directions) We measure the intensity of the light at a distance r from the source to be I. we move our measurement device to a distance of r/2. At this point we measure an intensity which is i) 4I ii) 2I iii) I/2 iv) I/4
Definition
 i) 4I   I∂ 1/r2 I= 1          (1/r)2 I= 1/4
Term
 In the figure above you are looking at the South pole of the permanent magnet. There is an attractive force between the permanent magnet and the stationary ring shown. When your eye is placed at this spot you observe that i) the current in the ring flows counterclockwise ii) the current in the ring flows clockwise iii) we cannot decide about in what direction is the current flowing in the ring iv) there cannot be a current in the ring
Definition
 ii) the current in the ring flows clockwise
Term
 At a given instant the electric field vector is in the vertical up direction and the magnetic field is pointing toward east direction. The electromagnetic wave is propagating toward i)the south ii)the north iii)the west iv)none of the above
Definition
 ii) the north
Term
 Charged negative ions after passing through a velocity selector enter a mass spectrometer and follow the trajectory 1 shown in the figure. There is no magnetic field in region A and there is a constant magnetic field in region B. Which one of the following statements is correct? i) the magnetic field in region B is perpendicular to the page and out the page ii) the magnetic field in region B is perpendicular to the page and into the page iii) the magnetic field in region B is in the plane of the paper and toward your right iv) the magnetic field in region B is in the plane of the paper and toward your left
Definition
 ii) the magnetic field in region B is perpendicular to the page and into the page
Term
 A wire is placed between the north and south poles of a magnet as shown. The magnetic force on the wire is perpendicular to the plane of the page and is out of the page. the direction of the current in the wire is i) from the top of the page to the bottom of the page ii) from the bottom of the page to the top of the page iii) parallel to the magnetic field iv) no statement can be made about the direction of the current
Definition
 ii) from the bottom of the page to the top of the page
Term
 A step-down transformer reduces the input voltage. In this case i) the current in the primary is the same as the current in the secondary since no charge can be created or destroyed ii) the current in the primary is more than the current in the secondary iii) the current in the primary is less than the current in the secondary iv) no statement can be made about the relation between the currents in the primary and the secondary
Definition
 iii) the current in the primary is less than the current in the secondary
Term
 At a given instant the electric field vector is in the veritcal up direction and the electromagnetic wave is propagating toward the east. At this instant, the magnetic field is pointing toward i) the south ii) the north iii) the west iv) none of the above
Definition
 i) south
Term
 A permanent magnet is made of a i) paramagnetic material ii) ferromagnetic material iii) diamagnetic material iv) all of the above
Definition
 ii) ferromagnetic material
Term
 At a given instant the electric field vector is pointing to the east and the electromagnetic wave is propagating toward the north. At this instant, the magnetic field is pointing i) up ii) down iii) toward the south iv) toward west
Definition
 ii) down
Term
 Protons of speed v enter the region between the poles of a magnet as shown in the figure and are deflected. Which one of the following statements is correct? i) the top magnet pole is a north pole ii) the top magnet pole is a south pole iii) both the top and the bottom poles are north poles iv) both the top and the bottom poles are south poles
Definition
 ii) the top magnet pole is a south pole
Term
 An external magnetic field is pointing out of the plane of a circular loop and decreasing. The induced current flows i) counterclockwise (CCW) in the circular loop ii) clockwise in the circular loop iii) no current is induced in the loop iv) first flows clockwise, then counterclockwise
Definition
 i) counterclockwise (CCW) in the circular loop
Term
 There is a current flowing in the single loop. Both the magnet and the loop are clamped in their positions and are stationary. The loop as shown in the figure is attracted the magnet but cannot move. As you look into the North pole of the magnet, i) the direction of the curent of the loop is determined by the direction of the induced current ii) the direction of the current cannot be determined if the magnet is not moving iii) as you look into the north pole of the magnet you see that the current in the loop is flowing counterclockwise iv) as you look into the north pole of the magnet you see that the current in the loop is flowing clockwise
Definition
 iii) as you look into the north pole of the magnet you see that the current in the loop is flowing counterclockwise
Term
 A step-up transformer increases the input voltage. In this case i) the output current is the same as the input current since no charge can be created or destroyed ii) the output current is larger than the input current iii) the output current is smaller than the input current iv) no statement can be made about the reltion between the currents in the primary and the secondary. We can only make statements about the input and output voltages.
Definition
 iii) the output current is smaller than the input current
Term
 Only one of the processes below does not induce an electric current in a conducting loop. i) expanding the area of the loop ii) increasing the magniture of a magnetic field perpendicular to the surface of the loop iii) decreasing the magniture of a magnetic field perpendicular to the surface of the loop iv) moving the loop parallel to a uniform magnetic field
Definition
 iv)moving the loop parallel to a uniform magnetic field
Term
 To start a fire by reflecting sun rays from a mirror one should use i) a convex mirror ii) a concave mirror iii) a plane mirror iv) one cannot start a fire using a mirror
Definition
 ii) a concave mirror
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