Physics II: Mini Exam 3 Lecture Questions
Two point charges are 4 cm apart. They are moved to a new separation of 8 cm. By what factor does the resulting mutual force between them change?
1/4
A ray of light is incident on a plane mirror and the angle of reflection is 50◦. What is the angle between the incident ray and the reflected ray?
100 (Angle of incidence = Angle of reflection)
A 100 g sample of a radioactive element has a half-life of 5 days. How many grams of radioactive material will remain after 15 days?
12.5 g (N = N0 e−λt)
If there are 146 neutrons in 238U (uranium), how many neutrons are found in the nucleus of 235U (uranium)?
143
If a hydrogen atom, originally in its ground state of energy−13.6 eV, absorbs a photon of energy 16.0 eV, then what is the resulting kinetic energy of the electron if the proton has negligible kinetic energy?
2.4 eV
Which of the following nuclear reaction equations correctly describes the alpha decay of 223 88Ra?
223 88Ra → 219 86Rn + 42He
How many fundamental interactions (forces)are there in the universe?
4
Which of the following is the α particle?
4 2He
Four 16 μF capacitors are connected in series. The equivalent capacitance of this combination is
4.0 μF (When two capacitors are connected in series, they act as a single equivalent capacitance with a value)
An object placed 2 m from a plane mirror is shifted by 0.5 m away from the mirror. What is the distance between the object and its image?
5.0 m
When a wire carries high current causing it to glow, it will emit which type of spectrum?
Continuous spectrum (Blackbody Spectrum)
A parallel beam of light is sent through an aquarium. If a convex glass lens is held in the water, it focuses the beam?
farther from the lens than outside the water.
A current in a long, straight wire produces a magnetic field. The magnetic field lines
form circles that go around the wire.
Isotopes of an element
have the same number of protons and electrons, but a different number of neutrons.
Two current-carrying wires are parallel as shown below; the current is the same in both wires. The current in both wires is flowing to the right. At the point P in the picture (Bottom wire), the direction of the net magnetic field is
into the screen
A Geiger counter is able to provide an indirect measure of radioactivity because radiation has the property of
ionizing matter.
According to the Rutherford experiment (and later model) of the atom, most of the volume of an atom:
is empty space.
A point charge Q is held fixed at the origin while an external force ~Fext is used to move a second charge q from point A to point B along the three different paths shown in the figure.The charge q begins from rest and has zero velocity when it reaches B. Is the work done by the external force largest along
is the work done by ~Fext the same for all three paths?
What is the resolution of a telescope?
its ability to distinguish two adjacent objects close together in the sky
The three loops of wire shown in the figure are all subject to the same uniform magnetic field that does not vary with time. Loop 1 oscillates back and forth as the bob in a pendulum, 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
The wire in the figure carries a current I that is increasing with time at a constant rate. The induced emf in each of the loops is such that
loop A has clockwise emf, loop B has no induced emf, and loop C has counterclockwise emf.
An ion is released from rest and moves due to the force from an electric field from a position in the field having a potential of14 V to a position having a potential of 8 V. The ion:
must have a positive charge.
An electric charge Q is located at a fixed position inside a magnetic field B. It feels
no force. Since the charge is not moving, there is no magnetic force.
According to Lenz's Law, which of the following effects characterizes an induced current in a conductor?
oppose the effect which produces it
The current-carrying wire as shown below is bent into a loop.At any point in the wire loop, the direction of the net magnetic field is:
out of the screen
Two current-carrying wires are parallel as shown below; the current is the same in both wires. The current in both wires is flowing to the right. At the point P in the picture (top wire), the direction of the net magnetic field is
out of the screen
Two current-carrying wires are parallel as shown below; the currents are now in the opposite directions. At a point midway between the wires (point A), the direction of the net magnetic field is
out of the screen
The figure shows a family of equipotential surfaces.If V1 > V2 > V3 > V4, is the object in the figure positively charged or negatively charged?
positive
The atomic number of a given element is equivalent to which of the following?
proton number in the nucleus
The atomic nucleus of any atom is made up of which of the following?
protons and neutrons
When a nucleus is divided into its constituents, energy is
released by the nucleus as it breaks apart.
Four 16 μF capacitors are now connected in parallel. The equivalent capacitance of this combination is
64.0 μF (When two capacitors are connected in parallel, they act as a single equivalent capacitance with a value)
What will you observe on the screen in an experiment using light incident on two slits?
A complicated pattern with numerous bright lines.
The figures below show ray diagrams for different types of contact lenses. Which of the following statements correctly describes the images formed by these contact lenses?
A contact lens can form a real or virtual image, depending on the type of lens.
Electrical charges and magnetic poles have many similarities, but one important "difference" is:
A magnetic pole cannot be isolated.
The primary coil of a transformer is connected to a battery, a resistor, and a switch. The secondary coil is connected to an ammeter. When the switch is thrown closed, the ammeter shows
A nonzero current for a short instant
A fish swims below the surface of the water at P. An observer at O sees the fish at?
A smaller depth than it really is.
A fish swims below the surface of the water. Let's suppose an observer is looking at the fish from point O ′ - straight above the fish. The observer sees the fish at?
A smaller depth than it really is.
If an electric field wave oscillates north and south (horizontally),and the electromagnetic wave is traveling vertically straight up, then what direction does the magnetic field wave oscillate?
East and west (horizontally)
When a high voltage is applied to a low-pressure gas causing it to glow, it will emit which type of spectrum?
Emission spectrum
A convex lens has a focal length of magnitude F . At which of the following distances from this lens would an object give an upright virtual image?
F/2
A convex lens has a focal length of magnitude F. At which of the following distances from this lens would an object give an upright virtual image?
F/2.
A double loop of wire (making 2 turns) is in the x -y plane centered at the origin. A uniform magnetic field is increasing at constant rate in the negative z direction. In which direction is the induced magnetic field in the loop?
In the positive z direction.
A Young's double-slit experiment is performed in air and then the apparatus is submerged in water. What happens to the fringe separation (d sin θ= m λ), and what can be used to explain the change, if any?
The separation decreases because the wavelength of the light decreases in the water.
Two current-carrying wires are parallel as shown below; the current is the same in both wires. The current in both wires is flowing to the right. What is the effect of the magnetic force?
The two wires attract each other.
The figure shows a current loop in a magnetic field. Is there a torque on the loop and, if so, in what direction?
There is a torque that tends to rotate the loop in direction (a), clockwise.
Which of the following about γ rays is true?
They have zero rest mass and a neutral charge.
A convex lens has a focal length of magnitude F . At which of the following distances from this lens would an object give an inverted virtual image?
This cannot be done with a convex lens.
A convex lens has a focal length of magnitude F. At which of the following distances from this lens would an object give an inverted virtual image?
This cannot be done with a convex lens.
A plane mirror forms an image that is?
Virtual and Upright.
A simple circuit consists of a resistor R, a capacitor C charges to a potential Vo, and a switch that is initially open but then thrown closed. Immediately after the switch is closed, the current in the circuit is?
Vo/R (V = IR)
A fish swims below the surface of the water at P . An observer at O sees the fish at
a smaller depth than it really is.
In the figure, an electron moves from the left to the right through a region in which the electric potential changed by∆V = 15,000 V. The corresponding change in the potential energy is ∆PE elec = −e ∆V = −15,000 eV. Suppose now that the electron is replaced by an oxygen ion O2−. What is the change in potential energy of the oxygen ion as measured in electron-volts?
-30,000 eV
When a light wave enters into a medium of different optical density?
Its speed and wavelength change.
The figure shows in part A an electric charge q moving pasta stationary bar magnet and in part B a bar magnet moving past a stationary electric charge. In which case will there be a magnetic force on the charge?
Only in A
Which of these is NOT a form of electromagnetic radiation?
Sound. Sound comes from pressure waves; all others are types ofEM radiation of different wavelengths.
Consider a metal shell with a hollow region inside. If the shell has a total charge Q and there is NO net charge inside the hollow region, what is true?
The electric field is zero in the metal part of the shell. The electric field is zero in the hollow part of shell. (this means the voltage/potential is constant)
Two current-carrying wires are parallel as shown below; the current is the same in both wires. The current in both wires is flowing to the right. At a point midway between the wires, the direction of the net magnetic field is
The field is zero.
A lens is used as a magnifier. Which of the following statements is INCORRECT?
The focal length of the lens must be negative.
When light is absorbed by an object, the radiation pressure is Pradiation = I/c. Suppose the exposed surface of an object has instead a reflective coating so that it reflects electromagnetic waves. Which of the following statements is true?
The force on the object due to radiation pressure is greater by a factor of two when the light is reflected.
What happens when I drop a magnet into a copper pipe (compared to a normal piece of metal)?
The magnet will fall more slowly than the metal piece.
In the US and Canada, the standard line voltage isVRMS = 110 V. In much of the world (Europe, Australia,Asia), the standard line voltage is VRMS = 220 V.The light output of a 60 Watt Tallahassee light bulb if used in Europe would
be four times as bright. P =V I =V 2 /R
That light can undergo interference is evidence that it:
behaves like a wave.
In figure (a), a solenoid produces a magnetic field whose strength increases into the plane of the page. An induced emf is established in a conducting loop surrounding the solenoid, and this emf lights bulbs A and B. In figure (b),points P and Q are shorted. After the short is inserted,
bulb A goes out; bulb B gets brighter.
Two light bulbs, A and B, are connected in series to a constant voltage source. When a wire is connected across B as shown, bulb A
burns more brightly.
Waves from a radio station have a wavelength of 250 m. These waves can travel directly from the antenna to a receiver or can reflect from a nearby mountain cliff and then reach the receiver.If the distance from the receiver to the cliff is L = 1000 m, is there
constructive
A long, straight wire carries a steady current I. A rectangular conducting loop lies in the same plane as the wire, with two sides parallel to the wire and two sides perpendicular. Suppose the loop is pushed toward the wire as shown in the figure. Given the direction of I, the induced current in the loop is
counterclockwise.
Doug rubs a piece of fur on a hard rubber rod, giving the rod a negative charge. What happens?
electrons are added to the rod
The atomic mass number of a nucleus is equivalent to which of the following numbers?
sum of neutron and proton numbers
A plastic comb can gain a net charge by combing hair.A charged comb attracts bits of paper because
the charge on the comb polarizes the charges in paper.
What is the conclusion from Faraday's Experiment? It shows that an electric current is produced in the wire loop only when
the magnetic field at the loop is changing. (A changing magnetic field produces an electric field.‹It is called induced electric field.The phenomenon is called electromagnetic induction.)
Which of the following best describes the image for a thin concave(diverging) lens that forms whenever the magnitude of the object distance is less than that of the lens' focal length?
upright, diminished and virtual
Which of the following best describes the image for a thin convex(converging) lens that forms whenever the object is at a distance less than one focal length from the lens?
upright, enlarged and virtual
A cylindrical piece of insulating material is placed in an external electric field, as shown. The net electric flux passing through the surface of the cylinder is
zero
A spherical surface surrounds a point charge at its center. If the charge is doubled and if the radius of the surface is also doubled, what happens to the electric flux ΦE out of the surface and the magnitude E of the electric field at the surface as a result of these doublings?
ΦE increases and E decreases.
