FINAL EXAM Flashcards
a charged conductor is brought near an uncharged insulator. which of the following statements is true?
a. both objects will repel
b. both objects will attract
c. neither object exerts an electrical force on the other
d. the objects will repel each other only if the conductor has a negative charge
e. the objects will attract each other only if the conductor has a positive charge
b
both positive and negative charges attract a neutral object
consider 3 identical metal spheres, A, B, and C. sphere A carries a charge of -2.0uC; sphere B carries a charge of -6.0uC; and sphere C carries a charge of +4.0uC. spheres A and B are touched together and then separated. spheres B and C are then touched and separated. does sphere C end up with an excess or deficiency of electrons, and how many is it?
a. deficiency, 6x10^13
b. excess, 3x10^13
c. excess, 2x10^13
d. deficiency, 3x10^12
e. there is no excess or deficiency of electrons
e
all have -4uC
a -4.0uC charge is located 0.45m to the left of a +6.0uC charge. what is the magnitude and direction of the electrostatic force on the positive charge?
a. 2.2N to the right
b. 2.2N to the left
c. 1.1N to the right
d. 1.1N to the left
e. 4.4N to the right
d
an electron is located between the plates of a parallel-plate capacitor. what is the magnitude and direction of the electric field such that the electric force exactly balances the weight of the electron so that it remains stationary?
at what point(s) in the vicinity of the fixed charges shown could a third charge of +2q be placed so that the net electrostatic force on it would be zero?
a. somewhere on the x-axis to the right of the +4q charge
b. somewhere on the x-axis between the 2 charges, but nearer to the -2q charge
c. somewhere on the x-axis to the left of the -2q charge
d. somewhere on the x-axis between the 2 charges, but closer to the +4q charge
e. at 2 points along the x-axis, one such point is to the left of the -2q charge and the other is to the right of the +4q charge
c
complete the following statement: the electron-volt is a unit of
a. electric field
b. charge
c. energy
d. electric potential
e. electric force
c
measured in J
as an electron moves against an electric field,
a. its electrical potential decreases and its potential energy increases
b. its electrical potential increases and its potential energy increases
c. its electrical potential increases and its potential energy decreases
d. its electrical potential decreases and its potential energy decreases
e. its electrical potential remains constant and its potential energy increases
c
two point charges are held at the corners of a rectangle as shown in the figure. the rectangle has a height of 0.050m and a width of 0.150m. determine the electric potential at corner A.
what direction is the electric field at B?
towards D
what is the change in electric potential energy when a charge of -1.0uC is moved from A to F to C to E?
a. -7.0x10^-5J
b. 7.0x10^-5J
c. 3.0x10^-5J
d. -3.0x10^-5J
e. -4.0x10^-5J
b
EPE=qV
= q (Vf - Vi)
= (-1x10^-6)(-40-(30))
= 7.0x10^-5J
the potential difference across the ends of a wire is doubled in magnitude. which of the following statements concerning the resistance of the wire is true?
a. the resistance increases by a factor of 4
b. the resistance increases by a factor of 2
c. the resistance is not changed
d. the resistance decreases by a factor of 2
e. the resistance decreases by a factor of 4
c
R=p(L/A)
resistors in series have the same (voltage / current) through them
current
resistors in parallel have the same (voltage / current) across them
voltage
for resistors in parallel, the total resistance is (greater than / equal to / less than) the value of any single resistor
less than
what is the equivalent resistance of the circuit?
7.5
what is the current through the 1.8 resistor?
a. 3.3A
b. 2.8A
c. 14A
d. 6.9A
e. 5.6A
2.8A
Vbat=IR = 3.33A
I1.8 < Ibat, so must be b
what is the potential drop across the 3.5 resistor?
a. 17V
b. 25V
c. 8.0V
d. 2.0V
e. 5.0V
V = IR
(0.55)(3.6) = 2.0V
the length of a certain wire is kept the same while its radius is doubled. what is the change in resistance of the wire?
a. the resistance increases by a factor of 4
b. the resistance increases by a factor of 2
c. the resistance is not changed
d. the resistance decreases by a factor of 2
e. the resistance decreases by a factor of 4
e
A=πr^2
geometry and composition
a 4A current is maintained in a simple circuit with a total resistance of 2. how much energy is delivered in 45 seconds?
P=IV
V=IR = (4A)(2) = 8V
P= (4A)(8V) = 32W
P = energy/time
energy = Pt = (32J/s)(45s) = 1440J
2 resistors are connected in parallel, and the combination connected to a DC power supply with voltage V as shown. if the current shown is 2A, what is the value of the battery voltage?
6V
R=3
V=IR = (2A)(3) = 6V
Kirchhoff’s loop rule is a statement of
a. the law of conservation of momentum
b. the law of conservation of charge
c. the law of conservation of energy
d. the law of conservation of mass
e. Newton’s second law
c
which of the following equations corrected represents a use of Kirchhoff’s loop rule for the circuit shown?
a. 2V = (6)I3 + 6V + (12)I1
b. 4V = (8)I2 + (12)I1
c. 4V + 6V + (12)I1 = (8)I2
d. 4V + 6V = (12)I1 + (8)I2
e. none of these
d
which of the following statements concerning permanent magnets is false?
a. the North Pole of a permanent magnet is attracted to the South Pole
b. all permanent magnets are surrounded by a magnetic field
c. the direction of the magnetic field is indicated by the North Pole of a compass
d. magnetic field lines outside a permanent magnet originate from the north pole and the end on the south pole
e
no magnetic monopoles
two particles move through a uniform magnetic field as shown. which of the following statements concerning these particles is true?
a. the particles may both me neutral
b. particle 1 is positively charged, 2 negatively
c. particle 1 is positively changed, 2 positively
d. particle 1 is negatively charged, 2 negatively
e. particle 1 is negatively charged, 2 positively
d
both CCW - same sign charges
a charged particle is moving in a uniform constant magnetic field. which of the following statements concerning the magnetic force exerted on the particle is false?
a. the magnetic force does no work on the particle
b. the magnetic force changes the velocity of the particle
c. the magnetic force can only act on a particle in motion
d. the magnetic force increases with the speed of the particle
e. the magnetic force does not change the kinetic energy of the particle
d
uniform circular motion
an electron moves with a speed of 8.0x10^6m/s. it enters a region where there is a magnetic field of 2.5T, directed at an angle of 60° to the velocity. calculate the magnitude of the magnetic force on the electron
F=qvBsinθ
F=(1.6x10^-19C)(8.0x10^6m/s)(2.5T)sin60
F=2.8x10^-12N
a proton is shot into a region containing both an electric field (shown) and a magnetic field (not shown). if the proton moves undeflected through the region with the fields, in what direction is the magnetic field?
into the page
a long straight wire carries a 40.0A current in the +x direction. at a particular instant, an electron is moving at 1.0x10^7m/s in the +y direction from the wire.
1) what is the direction of the force on the electron at this instant?
2) what is the magnitude of the force on the electron at this instant if r=.10m?
1) +x direction
2) B = uoI/2πr
(1.6x10^-19)(10^7)[((4πx10^-7)(40))/2π(0.1))] = 1.28x10^-16N
two long, straight, parallel wires separated by 0.10m carry currents in opposite directions as shown in the figure. determine the total magnetic field at point C, midway between the wires
the three loops of wire shown are all subject to the same uniform magnetic field. loop 1 swings back and forth, loop 2 rotates about a vertical axis, and loop 3 oscillates up and down at the end of a spring. which loop, or loops, will have an induced emf?
loop 2
no change in B, A, or θ for 1,3
θ changes in loop 2
a long straight wire carries current I that is to the right and increasing with time. the induced emf in each of the loops is such that
a. no emf is induced in any loop
b. all loops experience a counter clowise emf
c. loop A has a counterclockwise emf, loop B has no induced emf, and loop C has a clockwise emf
d. loop A has a clockwise emf, loop B has no induced emf, and loop C has a counterclockwise wise emf
e. loop A has a counterclockwise emf, loop B has a clockwise emf, and loop C has a clockwise emf
d
when more x’s are added, you must add more ______ and the rotation is _____
dots
CCW
when more dots are added, you must add more _____ and the rotation is _____
x’s
CW
which of the following statements concerning transformers is FALSE?
a. a transformer that steps up voltage, steps down current
b. they are an application of Faraday’s and Lenz’s laws
c. a transformer can function with either an ac current or a dc current
d. a transformer can function with either an ac current or a dc current
e. their operation makes use of induced emfs
d
transformers can only be used for _____ circuits
AC
a variable capacitor is connected to an ac sources. what effect does decreasing the frequency of the circuit have on the capacitive reactance and current?
capacitor increases
current decreases
in the circuit shown in the drawing, the generator supplies the same amount of current at either very small or very large frequencies. what can be deduced about the resistances R, R2, and R3 from this information?
a. R1=R2=R3
b. R1 = 2R2
c. R1 = R2
d. R1 = R3
e. R2 = R3
d
at low frequencies, no _____
capacitor
at high frequencies, no _____
inductor
an electromagnetic wave propagates along the +y direction as shown. if the E-field at the origin is along the +z direction, what is the direction of the B-field?
a. +x
b. -x
c. +y
d. -7
e. +z
f. -z
a
right hand rule
right hand rule for waves
thumb = velocity
fingers = electric field
palm = magnetic field
list the electromagnetic waves from longest to shortest
radio waves, microwaves, infrared, visible, ultraviolet, x-ray, gamma
a student looks at their reflection in a convex mirror. which of the following statements concerning their image is true?
a) their image must be real
b) the image is farther from the ornament than the student
c) the image is larger than the student
d) the image must be inverted
e) the image must be smaller than the student
e
a convex mirror has an image that is _____, size is _____, and is a _____ image
upright
smaller
virtual
an object is 1.0m in front of a mirror. a virtual image is formed 10.0m behind the mirror. what is the radius of curvature of the mirror?
1/f = 1/do + 1/di
1/f = 1/1 + 1/-10 = 1.11m
R=2f =2.2m
the inverted image of a light bulb is formed on a screen located 9.00m from a spherical mirror. the image is 4.00x larger than the light bulb. determine the object distance and the type of mirror used.
m = -4 = -di/do
do = di/4 = 9/4 = 2.25
concave
the figure shows the path of a portion of a ray of light as it passes through three different materials. what can be concluded concerning the refractive indices of these 3 materials?
a) n1 < n2 < n3
b) n1 < n2 < n3
c) n3 < n1 < n2
d) n2 < n1 < n3
e) n1 < n3 < n2
c
a ray of light passes from air into a block of glass with a refractive index of 1.59 as shown in the figure. what is the value of the distance D?
n1sinθ1 = n2 sinθ2
1sin50 = 1.59sinθ2
θ2 = 28.8
tan θ2 = D/4
D = 4tan28.8 = 2.19m
an object is placed 21cm from a diverging lens with a radius of curvature of 50cm. what is the magnification of the resulting image?
f=-R/2 = -25cm
1/f = 1/do + 1/di
1/-25 = 1/21 + 1/di
di = -11.4cm
m = -di/do
m = -(-11.4)/21 = .54
the near point of a farsighted person is 65cm. what power contact lens must they use to correct this visual problem and be able to read a book at a normal near point of 25cm?
P = 1/f
1/f = 1/do + 1/di
I/f = 1/.25 + 1/-0.65 = 2.5 diopters
in a Young’s double slit experiment, green light is incident on the 2 slits. the interference pattern is observed on a screen. which of the following changes would cause the fringes to be more closely spaced?
a) reduce the slit separation of distance
b) use red light instead of green light
c) use blue light instead of green light
d) move the screen farther from the slits
e) move the light source farther away from the slits
c
what is the minimum (non-zero) thickness of a benzene (n=1.501) thin film that will result in constructive interference when viewed at a normal incidence and illuminated with orange light (λ=615nm)? A glass slide (ng=1.620) supports the thin film
0 = mλ
λ = λ/h = 615/1.501 = 409nm
2+ = m(λ/2) = (1)409/2 = 204nm
as an electron moves opposite to an electric field the electric potential _____ and its electrical potential energy _____
increases
decreases
a proton is suspended (against the force of gravity) in uniform E field produced by a parallel plate capacitor. what do we know about this situation?
a) the top plate is positively charged
b) the top plate is negatively charged
c) the force exerted by the E field is less than the force of gravity
d) the force exerted by the E field is more than the force of gravity
e) we need more information
b
three capacitors are in parallel with each other in a circuit. their values are 4uF, 6.2uF, and 1.3uF respectively. their total capacitance is:
11.5uF
which of the following statements concerning resistors in series is true?
a) the voltage across each resistor is the same
b) the current through each resistor is the same
c) the power dissipated by each resistor is the same
d) the rate at which charge flows through each resistor depends on its resistance
e) the total current through the resistors is the sum of the current through each resistor
b
complete the following statement: A kw-hr is a unit of
a) electric force
b) electrical potential difference
c) energy
d) electric field strength
e) electric power
c
the constant epsilon knot is officially called _____ and what does this mean in simple terms
permeability of free space
resistance of a vacuum to an electric field
chose all the correct answers: which of the following variables, if changed, would change the capacitance of a given capacitor
a) A
b) Q
c) V
d) k
e) d
a, d, e
geometry: A, d
composition: k
a proton is shot with an initial speed of 2.50x10^5m/s towards P away from A. what will its speed just before hitting the plate at P?
two charges are placed on the x-axis. one charge is (q1=-13uC) is at x1=0cm and the other (q2=-39uC) is at x2=4.0cm.
at what point on the x axis is the electric field zero for the 2 charges?
somewhere between the 2 charges but closer to the -13uC
two charges are placed on the x-axis. one charge is (q1=-13uC) is at x1=0cm and the other (q2=-39uC) is at x2=4.0cm.
at which point (or points) on the x-axis near the charges is the electric potential zero?
V=V1+V2
k(q1/r1)+k(q2/r2)
both negative does not equal 0
never zero
two charges are placed on the x-axis. one charge is (q1=-13uC) is at x1=0cm and the other (q2=-39uC) is at x2=4.0cm.
what is the electric potential midway between the two charges
two charges are placed on the x-axis. one charge is (q1=-13uC) is at x1=0cm and the other (q2=-39uC) is at x2=4.0cm.
what would be the net electric field at 3.0cm to the right of the -13uC charge?
LONG ANSWER
a) what is the equivalent resistance of the circuit?
b) how much current flows through the 6.00 resistor?
c) what is the voltage across the 9.00 resistor?
d) how much energy does the 6.00 resistor use in 4 minutes?
an electron traveling due east in a region that contains only a magnetic field experiences a vertically downward force, toward the surface of the earth. what is the direction of the magnetic field?
due north
which of the following statements best explains why a constant magnetic field can do no work on a moving charged particle?
a) the magnetic force is conservative
b) the magnetic force is a velocity dependent force
c) the magnetic field is a vector and work is a scalar quantity
d) the magnetic force is always perpendicular to the velocity of the particle
e) the electric field of the particle cancels the effect of the magnetic field on the particle
d
in order to minimize power loss in electric transmission lines, you should transmit _____ current and _____ voltage using (DC/AC) power
low
high
AC
note the following circuit elements: (1) resistors, (2) capacitors, and (3) inductors. which of these elements uses no power, on average, in an AC circuit?
2 and 3
do resistors use power in an AC circuit?
yes
do capacitors use power in an Ac circuit?
no
do inductors use power in an AC circuit?
no
a transformer that steps up voltage steps down _____
current
true or false: the operation of a transformer makes use of mutual induction
true
true or false: a transformer can be used in an AC and DC circuit
false
only AC
a transformer that steps up current steps down _____
voltage
the impedance of an RCL circuit is dominated by the capacitance at _____ frequencies
low
true or false: the impedance of an RCL circuit is independent of frequency?
false
what frequency limit will the current going through the resistor be the greatest?
a) very low frequencies
b) at the resonant frequency of the circuit
c) at very high frequencies
d) depends on the specific values of L and C
explain
c
at high frequencies the current doesn’t go through the inductor. at low frequency it doesn’t gp through C so would not reach the resistor on both sides
true or false: electromagnetic waves carry energy
true
do x-rays or radio waves have longer wavelengths?
radio
true or false: in a vacuum, all electromagnetic waves travel at the same speed
true
true or false: lower frequency electromagnetic waves cannot be produced by oscillating circuits
false
true or false: energy is only carried by the electric field in an electromagnetic wave?
false
true or false: more energy is carried by the electric field than by the magnetic field
false
true or false: energy is carried equally by the electric and magnetic fields
true
the various colors of visible light differ in
a) frequency
b) wavelength
c) speed in vacuum
d) both frequency and wavelength
e) both frequency and speed in vacuum
d
c=λf = constant in vacuum
a plane mirror has an image that is _____
virtual
a plane mirror has a magnification of _____
+1
a plane mirror has a _____ image orientation
upright
white light enters a glass prism, but the color components of the light are observed to emerge from the prism. which of the following statements best explains this observation?
a) the separation of white light into its color components is due to the increase in the speed of the light within the glass
b) some of the color components of the white light are absorbed by the glass and only the remaining components are observed
c) the index of refraction of the glass depends on the wavelength, so the color components are refracted at different angles
d) only some of the color components are refracted by the glass, and these are the ones that are observed
e) white light is separated into its color components by total internal reflection within the prism
c
list steps for drawing ray diagrams
1) in through f, out parallel
2) in parallel, out through f
3) from C through top of object, reflect back
order the various kinds of EM radiation from least energetic to most energetic:
x-rays
infrared
microwaves
orange
radio
green
gamma-rays
ultraviolet
radio
microwaves
infrared
orange
green
ultraviolet
x-rays
gamma-rays
a concave mirror (converging lens) with the object outside the focal point has an image that is ______ and _____
inverted (m=-)
real
di = __ for a concave mirror (converging lens) that has an object outside the focal point
+
a concave mirror (converging lens) that has an object inside the focal point do ___ f
<
a concave mirror (converging lens) that has an object inside the focal point has an image that is _____ and _____
upright
virtual
a concave mirror (converging lens) that has an object inside the focal point has an image that is _____ than the object
larger
di = -
a convex mirror (diverging lens) has an image that is _____, _____ and _____ than the object
upright
virtual
smaller
di = -
locate the image produced by a concave mirror with the object outside the focal point using the 3 rays discussed
inverted
real
locate the image produced by a concave mirror with the object located inside the focal point
upright
larger
virtual
locate the image produced by a convex mirror
upright
virtual
smaller
two long, straight wires separated by 0.10m carry currents of 18A and 6A.
a) determine the magnetic field, including its direction, at the point P midway between the wires
b) a proton is now placed at mid point P and directed towards the top of the page with a speed 2.3x10^5m/s. find the magnetic force on the proton at this instant
an electromagnetic wave has an electric field with an average (rms) value of 250N/C. what is the energy delivered to a surface with an area of 0.75m^2 by this wave in one hour?
a conducting bar moves to the left on two conducting rails as shown. as a result of the bar moving through a constant external magnetic field, a current I is induced in the indicated orientation. what is the direction of the external magnetic field? explain
out of page
with bar moving left, area of loop is DECREASING so you are either losting dots or losing x’s
you know that whichever change you have the induced current goes CCW to oppose so the B induced is adding dots, this pairs with the change of losing dots so the external field is OUT OF THE PAGE
a woman stands 2.0m in front of a mirror and notices that her upright image height is 1/4 her actual height
a) what type of mirror is being used and how do you know
b) determine the focal length of the mirror
a ray of light in air strikes a block of quartz at an angle of incidence of 30 degrees. the angle of refraction is 20 degrees. what is the speed of light in quartz?
a diamond ring (n=2.42) submerged in benzene (n=1.51)
a) what is the critical angle when light moves from the diamond to benzene?
b) what is the critical angle when light moves from benzene to the diamond?
is a virtual image always larger than the object?
no
is a virtual image always smaller than the object?
no
is the virtual image always upright?
yes
is the virtual image inverted?
no
can a virtual image be photographed or projected onto a screen?
no
what are 2 things that you can change to change the focal length of a lens?
geometry - change R
composition - change n
during lab you place an object a known distance in front of a convex mirror with a known focal length. your lab partner does a calculation that shows the magnification is -2. after some thought, you should conclude that
a) your lab partners answer is correct
b) your lab partner made a mistake and the magnification is +2
c) your lab partner made a mistake and the magnification should be +1/2
d) your lab partner made a mistake and the magnification should be -1/2
c
upright, virtual, smaller, m+
a plastic plate (n=1.575) is submerged in ethyl alcohol (n=1.362)
what is the critical angle when light moves from ethyl alcohol to the plastic?
chromatic abberation affects (lenses / mirrors / both / neither)
name the optical phenomenon this is due to and why it physically occurs
lenses
dispersion
index of refraction has slight wavelength dependence
when an object is placed 25cm from a lens, a virtual image is formed. which of the following conclusions is/are incorrect?
a) the image is upright
b) the lens can be a converging lens
c) the image may be reduced or enlarged
d) if the lens is converging the image distance must be greater than 25cm
e) if the lens is diverging the image distance can be greater than 25cm
e
if case 2, converging, U, V, larger
if case 3, diverging, U, V, smaller
light that is incident upon the eye is refracted several times before it reaches the retina. in this process, at which boundary does the majority of the overall refraction occur?
a) lens/aqueous humor
b) air/cornea
c) lens/vittreous humor
d) aqueous humor/iris
e) vitreous humor/retina
b
what is wave-particle duality?
at the quantum scale everything can manifest wave and particle behavior, but not at the same time, depending on experimental circumstances
describe the term “work function”
the minimum energy required to remove electrons from a metal surface
the photon description of light is necessary to explain
a) polarization
b) Compton effect
c) diffraction of light
d) electron diffraction
e) interference of light
b
visible light has wavelengths between _____ and _____
400nm and 700nm
two glass plates are touching along the left edge and separated by a distance t on the right edge. when using light of wavelength 589nm, the 15th order dark fringe is observed to appear at the rightmost edge. what is the thickness of the air gap, t, on the right edge?
without his contact lenses, a student can focus on objects as close as 25cm, and as far away as 40cm. this student is (nearsighted / farsighted) and needs (converging / diverging) lenses to correct this vision problem. what refractive power of lenses does he require for normal vision?
nearsighted
diverging
P = 1/f = 1/do + 1/di
P = 1/infinity + 1/-0.40
P = -2.5 diopters
the work function of a nickel is 5.01eV
what is the longest wavelength light that can cause photoelectron emission from the nickel?
hf = Wo + KE
no KE - longets
hc/λ = Wo
λ = hc/Wo
((6.63x10^-34)(3x10^8))/(5.01(1.6x10^-19))
= 248nm
the work function of a nickel is 5.01eV
if light of wavelength 200nm was used, what maximum speed would ejected electrons have?
hf = Wo + KE
h(c/λ) = Wo + KE
KE = hc/λ - Wo = (((6.63x10^-34)(3x10^8))/(200x10^-19)) - 5.01(1.6x10^-19)
= 1.93x10^-19
KE = 1/2mv^2
v = (2KE)/(m) ^2 = (2(1.93x10^-19)/(9.1x10^-31))^1/2 = 6.5x1-^5m/s
if the intensity of the wavelength light was increased, what would happen to the maximum kinetic energy of the emitted photoelectrons and what would happen to the resulting photocurrent?
KE will remain the same
photocurrent will increase
which experimental evidence confirms the hypothesis that matter exhibits wave properties?
electron diffraction experiements
young’s double slit experiments
in an example of the Compton effect, a photon of wavelength 200 nm is scattered by an electron that is initially at rest. which of the following statements concerning the wavelength of the scattered photon is true
a) the wavelength is zero
b) the wavelength is 200nm
c) the wavelength is less than 200nm but greater than zero
d) the wavelength is greater than 200nm
e) not enough info
d
why is the resolution of scanning electron microscope (SEM) so much better than that of a traditional optical microscope?
Wsinθ = mλ
λelectron «_space;λlight
θelectron «_space;θlight
less diffraction means better resolution
the deBroglie wavelength of an electron is 1.2x10^-11m. determine the electron’s kinetic energy
λ=h/p = h/mv
v = h/mλ = (6.63x10^-34)/((9.1x10^-31)(1.2x10^-11m)) = 6.1x10^7m/s
KE = 1/2mv^2 = 1/2(9.1x10^-31)(6.1x10^7)^2
= 1.68x10^-15
which of the following would lower the uncertainty described in the Heisenberg Uncertainty Principle?
a) more accurate measuring instruments
b) nothing
c) enhanced technology
d_ using the metric system
e) taking more thorough data
e
