Physics Final
An electron moving in the +y-direction, at right angles to a magnetic field experiences a magnetic force in the -x-direction. The direction of the magnetic field is in the
+Z direction and out of the page
An electromagnetic wave travels in free space in the +y-direction, as shown. If the electric field at the origin is along the +z-direction, what is the direction of the magnetic field?
+x
For a certain electromagnetic wave in free space, at one instant the electric field vector in the +z-direction while the magnetic field vector points in the +x-direction, as shown. In what direction is this wave traveling?
+y
Three particles travel through a region of space where the magnetic field is out of the page as shown. What are the signs of these three particles?
1 is (-), 2 is (0), 3 is (+)
For an electromagnetic wave in free space having an electric field of amplitude E and a magnetic field of amplitude B, the ratio of B/E is equal to
1/c
During a period of high power demand, the voltage output of the power company is reduced by 5.0%. By what percentage is the power in a resistor decreased?
10%
What is the resonance frequency of an LC circuit consisting of 40microF capacitor and a 0.030H inductor?
145.36Hz
When a beam of light, originally travelling in air, enters a piece of glass having an index of refraction 3/2 its wavelength
2/3 speed in air
You are moving at a speed 2/3c toward Randy when he shines a light at you. At what speed do you see the light approaching you?
2/3c
A series RLC circuit has a peak voltage of 154V and a peak current of 5A. If the current lags the voltage by 45 degrees, what is the average power of the circuit?
272.2W
Two ideal parallel-plate capacitors are identical in every respect except that one has twice the plate area of the other. If the smaller capacitor has capacitance C, the larger one has capacitance
2C
A small charged plastic ball is vertically above another charged small ball in a frictionless test tube as shown in the figure. The balls are in equilibrium a distance d apart. If the charge on each ball is doubled, the equilibrium distance between the balls in the test tube would become
2d
A convex lens has a focal length f. If an object is located at "infinity" (very far away), the image formed is located at a distance from the lens
2f
A convex lens has focal length f. If an object is placed at a distance of 2f from the lens on the principal axis, the image is located at a distance from the lens
2f
If the index of refraction of a material is 2, this means that light travels
2x as fast in vacuum as it does in the material
When a dielectric material is introduced between the plates of a parallel-plate capacitor and completely fills the space, the capacitance increases by a factor of 4. What is the dielectric constant of the material that was introduced?
4
An ideal parallel-plate capacitor has a capacitance of C. If the area of the plates is doubled and the distance between the plates is halved, what is the new capacitance?
4C
A circuit has a resistance of 4.0ohms, a reactance due to the capacitance of 26 ohms, and a reactance due to the inductance of the 17ohms, find the impedance of the circuit.
9.85ohms
Four point charges of varying magnitude and sign are arranged on the corners of the square of side d as shown in the figure. Which one of the arrows shown represents the net force acting on the point charge with a charge +Q?
A
Three equal positive point charges +q are placed at the corners of a square of side d as shown in the figure. Which one of the arrows shown represents the direction of the net electric field at the center of the square?
A
Which one of the arrows shown in the figure best represents the direction of the electric field between the two uniformly charged metal plates?
A
Which statements about images are correct?
A virtual image cannot be formed on a screen
Three equal-magnitude point charges of varying signs are placed at three of the corners of a square of side d as shown in the figure. Which one of the arrows shown represents the direction of the net electric field at the vacant corner of the square?
B
Three equal negative point charges -q are placed at three of the corners of a square of side d as shown in the figure. Which one of the arrows shown represents the direction of the net electric field at the center of the square?
C
You are riding in a spaceship that has no windows, radios, or other means for you to observe or measure what is outside/ You wish to determine if the ship is stopped or moving at constant velocity. How can you do this?
Give up
A spaceship is moving away from the earth at a speed of 0.80c when it fires parallel to the direction of motion of ship. The missile moves at a speed of 0.60c relative to the ship. What would be the speed of the missile as measured by an observer on earth?
Greater than 0.80c but less than c
A wire is carrying current vertically downward. What is the direction of the force on the wire due to Earth's magnetic field?
Horizontally toward the East
Suppose you place an object in front of a concave mirror. Which of the following statements must be true?
If you position the object between the mirror and the focal point of the mirror, its image must be upright and virtual
Which of the following actions will increase the energy of a photon?
Increase its wavelength.
The plates of a parallel-plate capacitor are maintained with constant voltage by a battery as they are pulled apart. What happens to the strength of the electric field between the plates during this process?
It decreases
As the temperature of a blackbody increases, what happens to the peak wavelength of the light it radiates?
It gets shorter.
A beam of light travelling in air strikes a glass slab at an angle of incidence less than 90 degrees. After entering the glass slab, what does the beam of light do?
It slows down It will bend closer to the normal at the point of contact
A single-slit diffraction pattern is formed on a distant screen. Assuming the angles involved are small, by what factor will the width of the central bright spot on the screen change if the wavelength of the illuminating light is doubled?
It will double.
Light enters glass from air. The angle of refraction will be
Less than the angle of incidence
As shown in the figure, a metal bar is in contact with a pair of parallel rails and is in motion with an upward velocity of magnitude ν. A uniform magnetic field is present, directed downward as shown. The direction of the induced current through the resistor R is
No current is induced.
If a spherical convex/concave mirror has a radius of curvature R, the magnitude of its focal length is
R/2
The focal length of a convex mirror has a magntiude of 20cm. What is its radius of curvature?
R= 2(-F) R= 2(-20) R= -40cm
A vertical wire carries a current vertically downward. To the east of this wire, the magnetic filed points
South
A proton, moving in a uniform magnetic field, moves in a circle perpendicular to the field line, and takes time T for each circle. If the proton's speed tripled, what would now be it's time to go around each circle?
T
Observer A sees a pendulum oscillating back and forth in a relativistic rocket and measures its period to be TA. Observer B moves along with the rocket and measures the period to be TB. What is true about these two time measurements?
TA>TB
Which of the following statements is true for a series RLC as current in resonance?
The current in the circuit is a minimum. the inductance reactance is equal to the capacitance reactance.
Monochromatic coherent light shines through a pair of slits. If the wavelength of the light is decreased, which of the following statements are true of the resulting interference pattern?
The distance between the minima decreases.
Monochromatic coherent light shines through a pair of slits. If the wavelength of the light is decreased, which of the following statements are true of the resulting interference pattern? (There could be more than one correct choice.)
The distance between the minima decreases. The distance between the maxima decreases.
Monochromatic coherent light shines through a pair of slits. If the distance between these slits is decreased, which of the following statements are true of the resulting interference pattern? (There could be more than one correct choice.)
The distance between the minima increases. The distance between the maxima increases.
Which of the following statements about electromagnetic waves in free space are true?
The electric field vector is always at right angels to the magnetic field vector. The higher-frequency waves have shorter wavelengths than the lower-frequency wavelengths.
The figure shows electrons passing through a resistor. The arrow shows the direction in which the electrons are moving. Which of the following statements are correct? (There could be more than one correct choice.)
The electric potential is higher at point b than at point a.
A hydrogen nucleus, which has a charge +e, is situated to the left of a carbon nucleus, which has a charge +6e. Which statement is true?
The electrical force experienced by the hydrogen nucleus is to the left, and the magnitude is equal to the force exerted on the carbon nucleus.
Two very small plastic balls of equal mass are released from rest. One of them carries +10 µC of excess charge and the other one carries +1µC of charge. No other charges or fields are present. Which of the following statements are true about them as they move away from each other? (There may be more than one correct choice.)
The speed of the balls keeps increasing.
Radio waves are diffracted by large objects such as buildings, whereas light is not noticeably diffracted. Why is this?
The wavelength of light is much smaller than the wavelength of radio waves
Two protons are released from rest, with only the electrostatic force acting. Which of the following statements must be true about them as they move apart? (There could be more than one correct choice.)
Their electric potential energy keeps decreasing
A proton and an electron are released from rest, with only the electrostatic force acting. Which of the following statements must be true about them as they move toward each other? (There could be more than one correct choice.)
Their electric potential energy keeps decreasing. Their kinetic energy keeps increasing.
Given perfect lenses, what is the main reason that a telescope with a large-diameter objective lens can produce a sharper image than one with a small-diameter lens?
There is less diffraction with a larger lens than with a smaller lens.
Which of the following types of electromagnetic waves travels through space the fastest?
They all travel through a space at the same speed
An electron is initially moving to the right when it enters a uniform electric field directed upwards, as shown in the figure. Which trajectory (X, Y, Z, or W) will the electron follow in the field?
Trajectory Z
A ring with a clockwise current (as viewed from above the ring) is situated with its center directly above another ring, which has a counterclockwise current, as shown in the figure. In what directions is the net magnetic force exerted on the top of the ring due to the bottom ring?
Upward
The figure shows two unequal charges, +q and -Q. Charge -Q has greater magnitude than charge +q. Point X is midway between the charges. In what section of the line will there be a point where the resultant electric field is zero?
VW
Four charged particles (two having a charge +Q and two having a charge -Q) are arranged in the xy-plane, as shown in the figure. These particles are all equidistant from the origin. The electric potential (relative to infinity) at point P on the z-axis due to these particles, is
Zero
An electron moving along the +x-axis enters a magnetic field. If the electron experiences a magnetic deflection in the -y direction, then the magnetic field must have a component
along the -z-axis.
A really high-speed train moves in a direction parallel to its length with a speed that approaches c. The height of the train, as measured by a stationary observer on the ground
approaches 0
A current carrying a loop of wire lies flat on a horizontal tabletop. When viewed from above, the current moves around the loop in a counterclockwise sense. For points on the tabletop inside the loop, the magnetic field lines cause by this current
are straight up
The relativistic kinetic energy formula is valid
at all speeds
The image formed in a plane mirror is
at the same distance behind the mirror as the object in front of the mirror
The image formed in a plane mirror is
at the same distance behind the mirror as the object is in front of the mirror.
A negatively-charged plastic rod is brought close to (but does not touch) a neutral metal sphere that is connected to ground. After waiting a few seconds, the ground connection is removed (without touching the sphere), and after that the rod is also removed. The sphere is now a. neutral b. positively charged c. negatively charged
b. positively charged
If the voltage across a circuit of constant resistance is doubled, the power dissipated by that circuit will
be four times as large.
A convex lens has focal length f. If an object is placed at a distance between f and 2f from the lens on the principal axis, the image is located at a distance form the lens
between f and 2f
With what color light would you expect to be able to see the finest detail when using a microscope?
blue
A coil lies flat on a horizontal tabletop in a region where the magnetic field points straight down. The magnetic field disappears suddenly. When viewed from above, what is the direction of the induced current in this coil as the field disappears?
clockwise
A straight bar magnet is initially 4 cm long, with the north pole on the right and the south pole on the left. If you cut the magnet in half, the right half will
contain a north pole on the right and a south pole on the left.
A long, straight wire carrying a current is placed along the y-axis. If the direction of the current is in the +y direction, what is the direction of the magnetic field due to this wire as you view it in such a way that the current is coming directly toward you?
counterclockwise around the y-axis
Doubling the capacitance of a capacitor that is holding a constant charge causes the energy stored in that capacitor to
decrease to one-half
What principle is responsible for light spreading as it passes through a narrow slit?
diffraction
An capacitor consists of two large parallel plates of area A separated by a very small distance d. This capacitor is connected to a battery and charged until its plates carry charges +Q and -Q, and then disconnected from the battery. If the separation between the plates is now doubled, the potential difference between the plates will
double
According to the equation E=mc^2, an object turns into energy when it reaches the speed of light
false
As shown in the figure, one end of a metal bar is in contact with a circular rail and the other end is pivoted at P. A steady uniform, magnetic field B into the page is present. As the bar rotates about point P in a clockwise direction, the direction of the induced current through the resistor R is
from a to b.
The index of refraction of a type of glass is 1.50 and the index of refraction of water is 1.33. If light enters water from this glass, the angle of refraction will be
greater than the angle of incidence
In a double slit-interference experiment you are asked to use laser light of different wavelengths and determine the separation between adjacent maxima. You observe that his separation is greatest when you illuminate the double slit with
greater wavelength - red light
A wire is carrying current vertically downward. What is the direction of the force on this wire due to Earth's magnetic field?
horizontally towards the east
If a sheet containing a single thin slit heated (without damaging it) and therefore expands, what happens to the width of the central bright diffraction region on a distant screen ?
i gets narrower
Consider a capacitor connected across the ac source. As the capacitance is increased, the current through the capacitor will
increase
Which of the following changes would increase the separation between the bright fringes in the diffraction pattern formed by a diffraction grating?
increase the wavelength of the light used
A hydrogen atom consists of a proton and an electron. If the orbital radius of the electron increases, the electric potential energy of the electron due to the proton
increases
As you walk away from a plane mirror on a wall, the height of your image
is always the same size
An astronaut is resting on a bed inclined at an angle above the floor of a spaceship, as shown. From the POV of an observer who sees the spaceship moving near the speed of light parallel to the floor. The angle the bed makes with the floor
is greater than the angle observed by the astronaut
In a single-slit diffraction experiment, the width of the slit through which light passes is reduced. What happens to the width of the central bright fringe in the resulting diffraction pattern?
it becomes wider
A charged particle moving along the +x-axis enters a uniform magnetic field pointing along the +z-axis. Because of an electric field along the +y-axis, the charge particle does not change velocity. What is the sign of this particle?
it can be either positive or negative
In a double-slit experiment, it is observed that the distance between adjacent maxima on a remote screen is 1.0 cm. What happens to the distance between adjacent maxima when the slit separation is cut in half?
it increases to 2.0cm
A 30-year-old astronaut goes off on a long-term mission in a spacecraft that travels at speeds close to that of light. The mission lasts exactly 20 years at the end of the mission, the astronaut's age would be
less than 50 years
A double-slit interference experiment is performed in the air. Later, the same apparatus is immersed in benzene (which has an index of refraction 1.50) and the experiment is repeated. When the apparatus is in benzene, you observe that the interference fringes are
more closely spaced than when the apparatus is in air
A double-slit interference experiment is performed in the air. Later, the same apparatus is immersed in benzene (which has an index of refraction of 1.50), and the experiment is repeated. When the apparatus is in benzene, you observe that the interference fringes are
more closely spaced than when the apparatus is in air.
The plates of a parallel-plate capacitor are maintained with constant potential by a battery as they are pulled apart. During this process, the amount of charge on the plates
must decrease
A light beam has speed c in vacuum, and speed v in a certain plastic. The index of refraction of this plastic is
n= c/v
You are a passenger on a spaceship. As the speed of the spaceship increases, you will observe
no change in the length of your spaceship
The special theory is of relativity predicts that there is an upper limit to the speed of an object. It therefore follows that there is an upper limit in which of the following?
none of the above
If you were in a spaceship travelling close to the speed of light with respect to Earth, yo would notice that
none of the above occur
Two beams of coherent light start out at the same point in phase and travel different paths to arrive at point P. If the maximum destructive/constructive interference is to occur at point P, the two beams must travel paths that differ by
odd number of half-wavelengths whole number of wavelengths
Two light sources are said to be coherent if they are
of the same frequency and maintain a constant phase difference
Two light sources are said to be coherent if they are
of the same frequency, and maintain a constant phase difference.
When a light wave enters into a medium of different refractive index
only its speed and wavelength change
When an object moves close to the speed of light relative to earth, what happens to its dimensions compared to what they were before it began moving, as measured by an earth-based observer?
only lengths parallel to the direction of travel are decreased
A long straight wire carrying a 4-a current is placed along the x-axis as shown in the figure. What is the magnitude and direction of the magnetic field at a point P due to this wire? (p is on the y-axis and distance from origin is 1cm)
out of the plane of the page
A rectangular coil with corners labeled ABCD has length L and width W. It is placed between the poles of a magnet as shown. If there is a current I flowing through this coil in the direction shown, what is the direction of the force on section AB of this coil?
perpendicular and into the page
In an electromagnetic wave in free space, the electric and magnetic fields are
perpendicular to one another and perpendicular to the direction of wave propagation
Which of the following gives the correct order of the electro magnetic waves from longer wavelength to shorter wavelength?
radio waves, microwaves, infrared, visible, UV, x-rays, gamma ray
Which of the following lists gives the correct order of the the electromagnetic spectrum from low to high frequencies?
radio waves, microwaves, infrared, visible, UV, x-rays, gamma rays
In an RLC ac circuit, the values of the inductance and capacitance are both doubled. As a result of this change, the resonance frequency of the circuit is
reduced to one-half the original value.
Consider a solenoid of length L, N windings and radius b (L is much longer than b). A current I is flowing though the wire windings. If the radius of the solenoid is doubles to 2b, the magnetic filed inside the solenoid will
remain the same
Which of the following is not an electromagnetic wave?
sound waves
Which one of the following is not an electromagnetic wave?
sound waves
Monochromatic coherent light shines through a pair of slits. If the distance between these slits is decreased. Which of the following statements are true of the resulting interference pattern?
the distance between the minima increases the distance between the maxima increases
Which of the following statements about the image formed by a single diverging lens are true?
the image is always upright the image is always virtual
if the magnification of a mirror or lens is negative it means that
the image is inverted
An object is placed to the left of a spherical mirror in front of the mirror. If the image of the object is formed on the right side of the mirror, which of the following statements must be true?
the image is upright and virtual - concave/convex
Kirchhoff's junction rule is a statement of
the law of conservation of charge.
Increasing the intensity of a beam of light without changing its color will increase
the number of photons per second traveling in the beam.
A spaceship travelling at constant velocity passes by Earth and later Mars. In which frame of reference is the amount of time separating these two events the proper time?
the spaceship frame of reference
Which of the following are basic postulates of special relativity?
the speed of light is the same for all observers
An electron moving south, enters a magnetic field. Because of this field, the electron curves upward. We may conclude that the magnetic field must have a component
to the west
A proton, moving north, enters a magnetic field. Because of this field, the proton curves downward. We may conclude that the magnetic field must have a component
toward the east
A long straight, horizontal wire carries current toward the east. A proton moves toward the east along side and just south of the wire. What is the direction of the magnetic force on the proton?
toward the north
A vertical wire carries a current straight up in a region where the magnetic field vector points toward the north. What is the direction of the magnetic force on this wire?
toward the west
An electron, moving west, enters a magnetic field. Because of this field the electron curves upward. We may conclude that the magnetic field must have a component
towards the North
A proton, moving north, enters a magnetic field. Because of this field the electron curves downward. We may conclude that the magnetic field must have a component
towards the east
A vertical wire carries a current straight up in a region where the magnetic field vector points toward the north. What is the direction of the magnetic force on the wire?
towards the west
In a RLC circuit, the values of the inductance are both halved. As a result of the change, the resonance frequency of the circuit is
twice the original value
Four tiny charged particles (two having a charge +Q and two having a charge -Q) are distributed on the x- and y-axes as shown in the figure. Each charge is equidistant from the origin. In which direction is the net electric field at the point P on the y-axis?
upwards and towards the left
if an object is placed between a convex lens and its focal point, the image formed is
virtual and upright
Sometimes when you look into a curved mirror you see a magnified image (a great big you) and sometimes you see a diminished you (a little you). If you look at the bottom (convex) side of a shiny spoon, what will you see?
you will see a little you, right side up
