Physics 115 Mastering Physics

25 July 2022
4.7 (114 reviews)
133 test answers

Unlock all answers in this set

Unlock answers (129)
question
In the video, the temperature of the gas inside the fire piston increased because
answer
Work was done on the gas when the plunger was depressed.
question
Which physical law underlies the first law of thermodynamics?
answer
conservation of energy
question
When the quantity Q is greater than zero, __________ is added to the system.
answer
heat
question
When the quantity W in the first law is greater than zero, it refers to the __________.
answer
work done on the system
question
The quantity ΔEth in the first law of thermodynamics is the change in the __________ of the system.
answer
thermal energy
question
If heat is added to a system (Q>0) and no change in thermal energy of the system occurs (ΔEth=0), then the system must do __________ work on the outside world.
answer
positive
question
The second law of thermodynamics imposes what limit on the efficiency of a heat engine?
answer
A heat engine must deposit some energy into a cold reservoir
question
A refrigerator is an example of a __________.
answer
heat pump
question
If we assume a typical efficiency for the body, as quoted in the video, how much energy input would it take to climb a ladder, increasing your body's potential energy by 5,000 J?
answer
20,000 J
question
A typical efficiency of the human body is about _____.
answer
25%
question
A machine uses 1000 J of electric energy to raise a heavy mass, increasing its potential energy by 300 J. What is the efficiency of this process?
answer
30%
question
The entropy of an isolated system _________.
answer
either increases or remains constant
question
In the video, we use the atomic model to describe pressure as resulting from
answer
The force from the collision of gas molecules with the walls of their container
question
An atom's atomic mass number is the number of its ______.
answer
protons + neutrons
question
The three different gas-law processes described in this video are
answer
Constant volume, constant pressure, and constant temperature.
question
A sample of nitrogen gas is inside a sealed container. The container is slowly compressed, while the temperature is kept constant. This is a(n) ________ process
answer
isothermal
question
A sample of nitrogen gas is in a sealed container with a constant volume. Heat is added to the gas. The pressure __________
answer
increases
question
When the temperature of an ideal gas is increased, which of the following also increases?
answer
the average kinetic energy of the gas atoms
question
Which type of heat transfer can happen through empty space?
answer
radiation
question
Heat is added to each block at the same constant rate until it reaches a temperature of 500 K. Which of the following statements is true?
answer
The iron takes less time than the aluminum to reach the final temperature.
question
When the two materials have reached thermal equilibrium, the block of aluminum is cut in half and equal quantities of heat are added to the iron block and to each portion of the aluminum block. Which of the following statements is true?
answer
The blocks remain in thermal equilibrium.
question
Due to concerns about the toxic properties of mercury, many thermometers are made with other liquids. Consider draining the mercury from the above thermometer and replacing it with another, such as alcohol. Alcohol has a coefficient of volume expansion 5.6 times greater than that of mercury. The amount of alcohol is adjusted such that when placed in ice water, the thermometer accurately records 0∘C . No other changes are made to the thermometer. When the alcohol thermometer is placed in 20∘C water, what temperature will the thermometer record?
answer
greater than 20∘C
question
When the alcohol thermometer is placed in a −10∘C substance, what temperature will the thermometer record?
answer
less than −10∘C
question
If you want to design a thermometer with the same spacing between temperature markings as a mercury thermometer, how must the diameter of the inner hollow cylinder of the stem of the alcohol thermometer compare to that of the mercury thermometer? Assume that the bulb has a much larger volume than the stem.
answer
√(5.6) times wider
question
Which of the following pairs of terms are used to describe what is happening in the video?
answer
phase change, calorimetry
question
When steam condenses into water, __________
answer
heat is given off by the water
question
The defining equation for calorimetry is __________
answer
Q1 + Q2 = 0
question
To understand the heat conduction formula and the variables in it. Conduction—the flow of heat from a hotter object to a cooler object or from a hotter region to a cooler region of the same object—is the most common mechanism of heat transfer. The formula governing this is H=ΔQΔt=kA(TH−TCL), where H is known as the heat current. This formula applies to ________________.
answer
any object of cross-sectional area A, length L, and thermal conductivity k
question
The quantity ΔQ/Δt is the rate of heat transfer from the hot to the cold end of the rod
answer
true
question
The quantity ΔQ/Δt is the rate of heat added to the hot end of the rod to maintain its temperature.
answer
true
question
The quantity ΔQ/Δt is the rate of heat removed from the cold end of the rod to maintain its temperature.
answer
true
question
The quantity ΔQ/Δt is the total amount of heat transferred from the hot to the cold end of the rod
answer
false
question
In the SI system of units, what are the units of the quantity ΔQ/Δt
answer
watts
question
The thermal conductivity of copper _________ than that of stainless steel.
answer
is greater
question
The pot needs to distribute energy evenly over the bottom to cook the food evenly, so it needs to have _______ conductivity. The handle thermal conductivity_________ , so it won't get so hot and burn the hands.
answer
high, is smaller
question
What is the SI unit of pressure?
answer
the pascal
question
The pressure inside a latex balloon is nearly the same as the pressure outside. If you let a helium balloon go, and if, as it rises, it stays at a constant temperature, the volume of the balloon will
answer
increase
question
Salt water has a greater density than fresh water. Given this, there are objects that will
answer
float in salt water but sink in fresh water
question
The buoyant force on an object submerged in a liquid depends on __________
answer
the density of the liquid
question
When a viscous fluid flows in a tube, its velocity is __________
answer
greatest at the center of the tube
question
If you place a charged object next to an uncharged object that is a conductor,
answer
There is an attractive force between the two objects
question
There is a force between two charged objects. To decrease the magnitude of the force, we can
answer
Move the objects farther from each other or reduce the charge on either of them.
question
Coulomb's law describes __________
answer
the force between two point charges
question
A neutral object __________.
answer
has no net charge
question
A negatively charged rod is brought near a neutral metal sphere. Which of the following is true?
answer
There is an attractive force between the rod and sphere.
question
A small metal ball is given a negative charge, then brought near (i.e., within about 1/10 the length of the rod) to end A of the rod (Figure 1) . What happens to end A of the rod when the ball approaches it closely this first time?
answer
it is strongly attracted
question
After a great many contacts with the charged ball, how is the charge on the rod arranged (when the charged ball is far away)?
answer
There is a negative charge spread evenly on both ends
question
How does end A of the rod react when the charged ball approaches it after a great many previous contacts with end A? Assume that the phrase "a great many" means that the total charge on the rod dominates any charge movement induced by the near presence of the charged ball.
answer
It is strongly repelled
question
How does end B of the rod react when the charged ball approaches it after a great many previous contacts with end A?
answer
it is strongly repelled.
question
A glass marble is rubbed against a piece of silk. As a result the piece of fabric acquires extra electrons. What happens to the glass marble?
answer
The marble has lost the same number of electrons acquired by the piece of silk The marble acquires a positive charge and attracts the piece of silk.
question
Two glass marbles (1 and 2), each supported by a nylon thread, are rubbed against a piece of silk and then are placed near a third glass marble (3), also supported by a similar thread. Assuming that marble 3 has not been in contact with the piece of fabric, which of the following statements best describes the situation when the three marbles are brought together? To keep things simple in this Tutorial, we will ignore the effects of polarization and just focus on the overall charge of each object.
answer
Marbles 1 and 2 repel each other, but no interaction occurs with marble 3.
question
What is the final charge on each sphere if C is touched to B, removed, and then touched to A?
answer
3q/8, -q/4, 3q/8
question
Starting again from the initial conditions, what is the charge on each sphere if C is touched to A, removed, and then touched to B?
answer
q/2, 0, 0
question
The field inside a charged parallel-plate capacitor is __________
answer
uniform
question
The electric field direction is defined by the direction of the force felt by
answer
A positive charge
question
The electric field inside a metallic conductor is _____
answer
zero
question
For the charge distribution provided, indicate the region (A to E) along the horizontal axis where a point exists at which the net electric field is zero. (Figure 1) If no such region exists on the horizontal axis choose the last option (nowhere).
answer
C
question
For the charge distribution provided, indicate the region (A to E) along the horizontal axis where a point exists at which the net electric field is zero. (Figure 2) If no such region exists on the horizontal axis choose the last option (nowhere).
answer
B
question
For the charge distribution provided, indicate the region (A to E) along the horizontal axis where a point exists at which the net electric field is zero. (Figure 3) If no such region exists on the horizontal axis choose the last option (nowhere).
answer
nowhere
question
For the charge distribution provided, indicate the region (A to E) along the horizontal axis where a point exists at which the net electric field is zero. (Figure 4)
answer
A
question
A small object A, electrically charged, creates an electric field. At a point P located 0.250 m directly north of A, the field has a value of 40.0 N/C directed to the south. What is the charge of object A?
answer
−2.78×10−10 C
question
If a second object B with the same charge as A is placed at 0.250 m south of A (so that objects A and B and point P follow a straight line), what is the magnitude of the total electric field produced by the two objects at P?
answer
50.0 N/C
question
Consider the following configuration of fixed, uniformly charged spheres in (Figure 1) : a blue sphere fixed at the origin with positive charge q, a red sphere fixed at the point (d1,0) with unknown charge qred, and a yellow sphere fixed at the point (d2cos(θ),−d2sin(θ)) with unknown charge qyellow. The net electric force on the blue sphere has a magnitude F and is directed in the − y direction. What is the sign of the charge on the yellow sphere?
answer
negative
question
What is the sign of the charge on the red sphere?
answer
positive
question
Suppose that the magnitude of the charge on the yellow sphere is determined to be 2q. Calculate the charge qred on the red sphere. Express your answer in terms of q, d1, d2, and θ.
answer
2qcos(theta) (d1/d2)^2
question
As in the video, we apply a charge +Q to the half-shell that carries the electroscope. This time, we also apply a charge -Q to the other half-shell. When we bring the two halves together, we observe that the electroscope discharges, just as in the video. What does the electroscope needle do when you separate the two half-shells again?
answer
It does not deflect at all.
question
What are the units of potential difference?
answer
V
question
In other units, 1 V is equal to
answer
1 J/C
question
Rank in order, from highest to lowest, the electric potentials at points a, b, and c. Rank from highest to lowest. To rank items as equivalent, overlap them.
answer
a=c, b
question
What would be the potential at B if a 40 nC charge were moved from A to B?
answer
V = 150V
question
Mustang Sally just finished restoring her 1965 Ford Mustang car. To save money, she did not get a new battery. When she tries to start the car, she discovers that the battery is dead (an insufficient or zero voltage difference across the battery terminals) and so she will need a jump start. Here is how she accomplishes the jump start: She connects a red jumper cable (wire) from the positive terminal of the dead battery to the positive terminal of a fully functional new battery. She connects one end of a black jumper cable to the negative terminal of the new battery. She then connects the other end of the black jumper cable to the negative terminal of the dead battery. The new battery (now in a parallel with the dead battery) is now part of the circuit and the car can be jump started. The car starter motor is effectively drawing current from the new battery. After the car with the dead battery is running, the cables can be disconnected in the reverse order that they were connected. While unhooking the jumper cables, the positive and negative cables almost touch and a spark jumps between the ends of the cables. This spark is caused by the movement of electrons through the air between the battery terminals. In what direction are the electrons traveling during the spark?
answer
The electrons are traveling from the negative to the positive terminal.
question
There is a 12 V potential difference between the positive and negative ends of the jumper cables, which are a short distance apart. An electron at the negative end ready to jump to the positive end has a certain amount of potential energy. On what quantities does this electrical potential energy depend?
answer
only the potential difference and the charge
question
Assume that two of the electrons at the negative terminal have attached themselves to a nearby neutral atom. There is now a negative ion with a charge −2e at this terminal. What are the electric potential and electric potential energy of the negative ion relative to the electron?
answer
The electric potential is the same and the electric potential energy is twice as much.
question
What is the electric potential energy of an electron at the negative end of the cable, relative to the positive end of the cable? In other words, assume that the electric potential of the positive terminal is 0 V and that of the negative terminal is −12V. Recall that e=1.60×10−19C.
answer
1.92x10^-18 J
question
At the negative terminal of the battery the electron has electric potential energy. What happens to this energy as the electron jumps from the negative to the positive terminal?
answer
It is converted to kinetic energy
question
If you wanted to move an electron from the positive to the negative terminal of the battery, how much work W would you need to do on the electron?
answer
1.92x10^-18 J
question
The electric potential inside a parallel-plate capacitor __________
answer
increases linearly from the negative to the positive plate
question
The field between two charged parallel plates is kept constant. If the two plates are brought closer together, the potential difference between the two plates
answer
Decreases
question
New units of the electric field were introduced in this chapter. What are they?.
answer
V/m
question
The electron volt is a unit of __________.
answer
energy
question
What are the units of potential difference?
answer
volts
question
The electric field __________
answer
is always perpendicular to an equipotential surface
question
You can increase the capacitance of a capacitor by
answer
Both A and D
question
What property of objects is best measured by their capacitance?
answer
the ability to store charge
question
Consider an air-filled charged capacitor. How can its capacitance be increased?
answer
Decrease the spacing between the plates of the capacitor.
question
Consider a charged parallel-plate capacitor. How can its capacitance be halved?
answer
Double the plate separation Halve the plate area
question
Consider a charged parallel-plate capacitor. Which combination of changes would quadruple its capacitance?
answer
Halve the plate separation and double the plate area.
question
If the spacing between the plates, d, is the same in both capacitors, and the voltage across capacitor 1 is V, what is the voltage across capacitor 2?
answer
V/2
question
If the spacing between the plates in capacitor 1 is d, what should the spacing between the plates in capacitor 2 be to make the capacitance of the two capacitors equal?
answer
2d
question
Current from a charged capacitor lights a bulb. As time goes on, the brightness of the bulb
answer
decreases
question
You can decrease the resistance of a length of wire by
answer
cooling it
question
A lightbulb is rated by the power that it dissipates when connected to a given voltage. For a lightbulb connected to 120 V household electricity, decreasing the resistance of the filament will _____ the current through the bulb and _____ the power dissipated by the bulb
answer
increase, increase
question
The charge carriers in metals are _____
answer
electrons
question
A battery is connected to a resistor. Increasing the resistance of the resistor will __________
answer
decrease the current in the circuit
question
A battery is connected to a resistor. As charge flows, the chemical energy of the battery is dissipated as _________
answer
thermal energy
question
The equation I = Δ V/R is called
answer
Ohm's law
question
The laws shown in the video—Kirchhoff's junction law and Kirchhoff's loop law—are not newly introduced laws of physics. The junction law is based on __________, and the loop law is based on __________
answer
Conservation of charge, conservation of energy
question
In a series circuit of two resistors, the resistors have the same __________; in a parallel circuit of two resistors, the resistors have the same __________
answer
Current through them, voltage across them
question
The symbol shown represents a _____
answer
battery
question
The bulbs in the circuit below are connected __________
answer
in series
question
Which terminal of the battery has a higher potential?
answer
the top terminal
question
When three resistors are combined in series, the total resistance of the combination is __________
answer
greater than any of the individual resistance values
question
Signal propagation in the nervous system can be modeled as
answer
A series of RC circuits
question
In an RC circuit, what is the name of the quantity represented by the symbol τ?
answer
the time constant
question
What is the reading V of the voltmeter? Express your answer in terms of the EMF E.
answer
V = E
question
The voltmeter, as can be seen in the figure, is connected to points 1 and 3. What are the respective voltage differences between points 1 and 2 and between points 2 and 3?
answer
0;E
question
What is the reading I of the ammeter? Express your answer in terms of E and R
answer
I = ER
question
What is the reading of the ammeter now? Express your answer in terms of E, r, and R.
answer
I = E/R+r
question
What is the reading of the voltmeter now? Express your answer in terms of E, r, and R.
answer
V = ER/R+r
question
Rank below the three identical resistors (A, B, and C) in (Figure 1) on the basis of the current that flows through them. Rank from largest to smallest. To rank items as equivalent, overlap them.
answer
A = B,C
question
Rank below the three identical resistors (A, B, and C) in (Figure 2) on the basis of the current that flows through them. Rank from largest to smallest. To rank items as equivalent, overlap them.
answer
C, A=B
question
Rank below the four identical resistors (A, B, C, and D) in (Figure 3) on the basis of the current that flows through them. Rank from largest to smallest. To rank items as equivalent, overlap them.
answer
D, A, B=C
question
How does the current through R1 compare with the current through R2 immediately after the switch is first closed?
answer
The current through R1 is greater than the current through R2.
question
How does the current through R1 compare with the current through R2 a very long time after the switch has been closed?
answer
The current through R1 is equal to the current through R2.
question
How does the current through R1 compare with the current through R2 immediately after the switch is opened (after being closed a very long time)?
answer
The current through R1 is less than the current through R2.
question
Magnetic field lines form closed loops
answer
All of the above.
question
Compasses line up with magnetic fields. A compass will line up
answer
Parallel to magnetic field lines, with the north pole pointing in the direction of the field
question
A compass in a magnetic field will line up __________
answer
with the north pole pointing in the direction of the magnetic field
question
The direction of the magnetic force on a moving charged particle in a magnetic field is __________
answer
both perpendicular to the velocity and perpendicular to the magnetic field
question
A magnet will exert a force on
answer
All of the above
question
The magnetic field lines due to a straight, current-carrying wire are __________
answer
circles around the wire
question
A loop of wire carries a current. The resulting magnetic field __________
answer
is similar to that of a bar magnet perpendicular to the plane of the loop
question
Two parallel wires carry a current in the same direction. There is ___________ between the wires
answer
an attractive force
question
The magnetism of a permanent magnet results from __________
answer
the magnetic moments of electrons in the material making up the magnet
question
In this video, we see that a _____ magnetic field can create an electric current
answer
changing
question
Which of the following will cause an induced current in a coil of wire?
answer
a magnet being moved into or out of the coil
question
Lenz's law states that an induced magnetic field in a conductor
answer
Opposes the change in flux through the conductor
question
A metallic conductor moving at a constant speed in a magnetic field may develop a voltage across it. This is an example of __________
answer
motional emf
question
An emf is induced in response to a change in magnetic field inside a loop of wire. Which of the following changes would increase the magnitude of the induced emf?
answer
changing the magnetic field more rapidly
question
In a transformer, energy is carried from the primary coil to the secondary coil by
answer
the magnetic field in the iron core
question
A standard electrical outlet has three wires connected to it: the hot, the neutral, and the ground. There is no potential difference between which pair of wires?
answer
the neutral wire and the ground wire
question
We often refer to the electricity at a typical household outlet as being 120 V. In fact, the voltage of this AC source varies; the 120 V is __________
answer
the rms value of the voltage
question
A step-up transformer _____ the voltage and _____ the current
answer
raises/lowers