Physics 3 Final Exam-Ekwue
A solenoid is 3.0 cm long and has a radius of 0.50 cm. It is wrapped with 500 turns of wire carrying a current of 2.0 A. The magnetic field at the center of the solenoid is:
4.2 ´ 10-2 T
An ac generator producing 10 V (rms) at 200 rad/s is connected in series with a 50-W resistor, a 400-mH inductor, and a 200-mF capacitor. The rms current is:
0.135 A
Radio waves of wavelength 3 cm have a frequency of:
10,000 MHz
A generator supplies 100 V to the primary coil of a transformer. The primary has 50 turns and the secondary has 500 turns. The secondary voltage is:
1000 V
The reactance of a 35-mF capacitor connected to a 400-Hz generator is:
11 Ω
A concave spherical mirror has a focal length of 12 cm. If an object is placed 6 cm in front of it the image position is:
12 cm behind the mirror
An LC circuit has an inductance of 15 mH and a capacitance of 10 mF. At one instant the charge on the capacitor is 25 mC. At that instant the current is changing at the rate:
170 A/s
What is the minimum number of lines required in a diffraction grating to just resolve light with wavelengths of 471.0 nm and 471.6 nm in first order?
786
A loop of current-carrying wire has a magnetic dipole moment of 5.0 ´ 10-4 A×m2. If the dipole moment makes an angle of 57° with a magnetic field of 0.35 T, what is its potential energy?
-9.5 x 10-5 J
The diagram shows a straight wire carrying current i in a uniform magnetic field. The magnetic force on the wire is indicated by an arrow but the magnetic field is not shown. Of the following possibilities, the direction of the magnetic field is:
out of the page
Which one of the following experiments provides evidence that light consists of particle-like entities?
photoelectric effect
The magnetic field B inside a long ideal solenoid is independent of:
the cross-section area
When light travels from one medium into a different medium with a different index of refraction,
the speed and wavelength change but the frequency stays the same.
The statement that magnetic field lines form closed loops is a direct consequence of:
Gauss' law for magnetism
Which instrument uses a single converging lens with the object placed just inside the focal point?
Magnifying glass
The main reason that alternating current replaced direct current for general use is:
ac voltages may be conveniently transformed
A star is moving toward Earth at 90% the speed of light. The star emits light, which moves away from the star at the speed of light. What do Earth-based astronomers measure for the speed of this light?
c
Lines of the magnetic field produced by a long straight wire carrying a current are:
circles concentric with the wire
A square loop of wire lies in the plane of the page. A decreasing magnetic field is directed into the page. The induced current in the loop is:
clockwise
Lenz's law is a consequence of what other physical law?
conservation of energy
You are facing a loop of wire which carries a clockwise current of 3.0 A and which surrounds an area of 5.8 x 10−2m2. The magnetic dipole moment of the loop is:
0.17 A.m2, into the page
A converging lens is symmetric; its curved sides have radii of 50 cm. If the focal length is to be 80 cm, what should the index of refraction be?
1.3
A circular loop of wire with a radius of 20 cm lies in the xy plane and carries a current of 2 A, counterclockwise when viewed from a point on the positive z axis. Its magnetic dipole moment is:
0.25 A.m2, in the positive z direction
A particle with rest mass m moves with speed 0.6c. Its kinetic energy is:
0.25mc^2
A 26 cm diameter circular loop of wire lies in a plane perpendicular to a 0.90 T magnetic field. It is removed from the field in 0.15 s. What is the average induced emf?
0.319 V
A beam of x-rays of wavelength 0.20 nm is diffracted by a set of planes in a crystal whose separation is 3.1 x 10-8 cm. The smallest angle between the beam and the crystal planes for which a reflection occurs is:
0.33 rad
A current of 1 A is used to charge a parallel plate capacitor with square plates. If the area of each plate is 0.6 m2 the displacement current through a 0.3 m2 area wholly between the capacitor plates and parallel to them is:
0.5 A
An ac generator produces 10 V (rms) at 400 rad/s. It is connected to a series RL circuit (R = 17.3 W, L = 0.025 H). The rms current is:
0.50 A and lags the emf by 30°
A certain automobile is 6.0 m long if at rest. If it is measured to be 4.8 m long while moving, its speed is:
0.6c
A meter stick moves sideways (that is, in a direction perpendicular to its length) at 0.95c. According to measurements taken in the laboratory, its length is:
1.0 m
Photoelectric Effect: A photoelectric surface has a work function of 2.10 eV. Calculate the maximum kinetic energy, in eV, of electrons ejected from this surface by electromagnetic radiation of wavelength 356 nm. (1 eV = 1.60 × 10-19 J, c = 3.00 × 108 m/s, h = 6.626 × 10-34 J
1.39 ev
An electron in a hydrogen atom moves in a circle of radius 1.1 x 10-10 m at a speed of about 1.6 x 10^6 m/s. What is the magnetic dipole moment of this electron due to its orbital motion?
1.4 x 10^-23 J/T
A diffraction grating has 2000 lines. For an incident wavelength of 600 nm, what is the smallest wavelength difference (Δλ) this grating can resolve in the second order?
1.50 x 10^-10 m
A magnifying glass has a focal length of 15 cm. If the near point of the eye is 25 cm from the eye the angular magnification of the glass is about:
1.7
A strip 1.2 mm wide is moving at a speed of 25 cm/s through a uniform magnetic field of 5.6 T. What is the maximum Hall voltage across the strip?
1.7 mV
An RLC circuit has a capacitance of 12 mF, an inductance of 25 mH, and a resistance of 60 W. The current oscillates with an angular frequency of:
1.8 x 103 rad/s
The diagram shows the passage of a ray of light from air into a substance X. The index of refraction of X is:
1.9
The circuit shown is in a uniform magnetic field that is into the page. The current in the circuit is 0.20 A. At what rate is the magnitude of the magnetic field changing?
140 T/s
A set of twins, Andrea and Courtney, are initially 10 years old. While Courtney remains on Earth, Andrea rides on a spaceship that travels away from Earth at a speed of 0.60c for 10 years (as measured by Courtney). At the end of the trip, Courtney is 20 years old. How old is Andrea?
18 years
What is the minimum thickness of a soap bubble film (nsoap = 1.57) that will cause a destructive interference in the reflected light of a bright yellow (λ = 650 nm) overhead lamp? (assume there is air on both sides of the soap film).
2.07 x 10^-7 m
Light of wavelength 620 nm falls in a double slit, and the first bright fringe of interference pattern is seen at an angle of 15.0o with the horizontal. Find the separation between the slits.
2.40 μm
Two long straight wires enter a room through a window. One carries a current of 3.0 A into the room while the other carries a current of 5.0 A out. The magnitude of the path integral ∮B⇀.ds⇀ around the window frame is:
2.5 x10-6 T.m
X-rays of wavelength 1.7 x 10-11 m are found to undergo second order reflection at a Bragg angle of 40o from a SiO2 crystal. What is the inter-planar spacing (d) of the reflecting planes of the crystal?
2.65 x 10^-11 m
The total energy in an LC circuit is 5.0 ´ 10-6 J. If L = 25 mH the maximum current is:
20 mA
A millionairess was told in 1992 that she had exactly 15 years to live. However, if she immediately takes off, travels away from the Earth at 0.8 c and then returns at the same speed, the last New Year's Day the doctors expect her to celebrate is:
2017
A 45-m long wire is coiled so that it makes a coil containing 100 circular loops, one on top of the other. If the wire carries a current of 13 A, what is the magnetic dipole moment of the coil?
21 A·m2
An LC circuit consists of a 1 mF capacitor and a 4 mH inductor. Its oscillation frequency is approximately:
2500 Hz
A concave mirror forms a real image which is twice the size of the object. If the object is 20 cm from the mirror, the radius of curvature of the mirror must be about:
27 cm
A grating has 6600 lines/cm. How many spectral orders can be seen when it is illuminated by light of wavelength 390 nm?
3
What is the photon energy of red light having a wavelength of 6.40 nm?
3.10 × 10^-19 J
At one instant an electron (charge = -1.6 x 10-19 C) is moving in the xy plane, the components of its velocity being vx = 5.0 x 105 m/s and vy = 3.0 ´x 105 m/s. A magnetic field of 0.80 T is in the positive x direction. At that instant the magnitude of the magnetic force on the electron is:
3.8 x 10-14 N
A 0.20-cm radius cylinder, 3.0 cm long, is wrapped with wire to form an inductor. At the instant the magnetic field in the interior is 5.0 mT, the energy stored in the field
3.8 x 10-6 J
A beam of light traveling initially through air passes through three layers of transparent plastic as shown in the illustration below. At what angle does the light reflect from the third layer of plastic?
33 degrees
The index of refraction of benzene is 1.80. The critical angle for total internal reflection, at a benzene-air interface, is about:
34°
A transmitter consists of an LC circuit with an inductance of 15 µH and a capacitance of 23 pF. What is the wavelength of the electromagnetic waves it emits?
35 m
The magnetic flux through a coil of wire containing two loops changes from -80 Wb to +58 Wb in 0.72 s. What is the emf induced in the coil?
380 V
The wavelength of yellow sodium light in air is 589 nm. Determine its wavelength in glass whose index of refraction is 1.52.
388 nm
Two parallel wires, 4 cm apart, carry currents of 2 A and 4 A respectively, in the same direction. The force per unit length of one wire on the other is:
4 x10-5 N/m, attractive
Two long straight wires are parallel and carry current in the same direction. The currents are 8.0 and 12 A and the wires are separated by 0.40 cm. The magnetic field at a point midway between the wires is:
4.0 x 10-4 T
Two plane mirrors make an angle of 60° with each other. The maximum number of images of an object placed between them is:
5
A 1.2-m radius cylindrical region contains a uniform electric field along the cylinder axis. It is increasing uniformly with time. To obtain a total displacement current of 2.0 x 10-9 A through a cross section of the region, the magnitude of the electric field should change at a rate of:
50 V/m.s
The Hall effect can be used to calculate the charge-carrier number density in a conductor. If a conductor carrying a current of 2.0 A is 0.5 mm thick, and the Hall effect voltage is 4.5 µV when it is in a uniform magnetic field of 1.2 T, what is the density of charge carriers in the conductor?
6.7 x 10^27/m3
The impedance of the circuit shown is:
65 Ω
A 10-turn ideal solenoid has an inductance of 3.5 mH. When the solenoid carries a current of 2.0 A the magnetic flux through each turn is:
7.0 X 10-4 Wb
A 0.70-m radius cylindrical region contains a uniform electric field that is parallel to the axis and is increasing at the rate 5.0 x 1012 V/m×s. The magnetic field at a point 0.25 m from the axis has a magnitude of:
7.0 x 10^-6 T
If the electric field in a plane electromagnetic wave is given by Emsin[(3 x 106 m-1 x) - ωt], the value of ω is:
9 x 10^14 rad/s
A material having an index of refraction of 1.30 is used as an antireflective coating on a piece of glass (n = 1.50). What should the minimum thickness of this film be to minimize reflection of 500 nm light?
9.62 x 10^-8 m
The uncertainty in position of an electron in a certain state is 5 x10^-10 m. The uncertainty in its momentum could be: (There could be more than one correct answer. Select all that are correct).
A) 5.0 x 10-24 kg.m/s B) 1.4 x 10-25 kg.m/s C) 4.0 x 10-24 kg.m/s D) 2.1 x 10-25 kg.m/s E) 3.0 x 10-24 kg.m/s
Compton Scattering: A photon scatters off of a stationary electron. Which of the following statements about the photon are true? (There could be more than one correct choice.)
A) Its frequency increases due to the scattering. B) Its wavelength increases due to the scattering. C) Its energy does not change. D) Its wavelength decreases due to the scattering. E) Its frequency decreases due to the scattering.
A spatially uniform magnetic field CANNOT exert a magnetic force on a charged particle in which of the following circumstances? There may be more than one correct statement.
A) The particle moves at 45 degrees to the magnetic field. B) The particle is at rest. C) The particle moves parallel to the magnetic field. D) The particle moves perpendicular to the magnetic field. E) The magnitude of the magnetic field changes with time.
Consider two parallel wires carrying currents in opposite directions. One of the wires is above the other but not touching each other. Due to the magnetic interaction between the wires, the lower wire experiences a magnetic force that is
downward
Select the correct statement:
gamma rays have a higher frequency than infrared waves
. In the figure, there are three wires carrying currents in the indicated directions, and an Amperian loop. The sign of the contribution of the current in each wire to the path integral ∮B⇀.ds⇀{in Ampere's Law is:
i1 +, i2 -, i3 0
An electron moves in the negative x direction, through a uniform magnetic field that is in the negative y direction. The magnetic force on the electron is:
in the negative z direction
Electrons are going around a circle in a counterclockwise direction as shown. At the center of the circle they produce a magnetic field that is:
into the page
The magnetic flux ΦB through a surface:
is the amount of magnetic field piercing the surface.
In a purely capacitive circuit the current:
leads the voltage by one-fourth of a cycle
Because ferromagnets exhibit hysteresis, the magnetization:
may not vanish when an applied field is reduced to zero
For a power transmission line, the transmission should be at low current and high voltage because:
this minimizes transmission losses
Magnetic field lines inside the solenoid shown are:
toward the top of the page
An object is 2 m in front of a plane mirror. Its image is:
virtual, erect, and 2 m behind the mirror
