Practice Test 3-5 Of First & Second Law Of Thermodynamics – Physics
This chapter is about first & second law of thermodynamics, specific heat and latent heat – Physics.
A hydraulic jack has a mechanical advantage allowing a puny human to lift a car. Which of the following statements is true?
The work done by the input piston is equal to the work done by the output piston.
A hydraulic lift is designed with an output cylinder that has 36 times the area of the input cylinder. If a force F is applied to the input cylinder, the output cylinder can supply a force equal to
36 F
A hydraulic lift is designed with an input cylinder that has 1/5 the diameter of the output cylinder. If a force F is applied to the input cylinder, the output cylinder can supply a force equal to
25 F
Boyle’s Law can be stated mathematically as PV=constant. This translates to:
P and V are inversely proportional
Diving in your swimming pool, you let out a stream of bubbles. As they rise towards the surface they
increase in diameter.
According to Archimedes’ Principle, the bouyant force
is equal to the weight of the displaced fluid
A block of wood is floating in water with 2/3 of its volume below the water line. The density of the wood is
equal to 2/3 the density of water
Water flows through pipe A into pipe B. Pipe B is larger and has three times the cross-sectional area that pipe A has. Compared to the speed of the water in pipe A, the speed in pipe B is:
1/3
Water flows through a 2cm diameter pipe connected to a 1cm diameter pipe. Compared to the speed of the water in the 2cm pipe, the speed in the 1cm pipe is:
quadrupled
A large gravel truck is loosely covered with a tarpaulin. The edges of the tarp are tied down to the truck. When the truck is at rest the tarp is flat. When it cruises at highway speeds
the tarp bows up
Absolute zero temperature
-is the temperature where all molecular motion ceases.
– can never be reached by cooling any object.
– is -273.2 degrees Celsius.
When two objects at different temperatures are placed in thermal contact, heat flows
from the higher temperature object to the lower temperature object.
The amount of heat necessary to change the temperature of 1 gram of substance by 1 degree Celsius is called the substance’s
specific heat
Latent heat is always
involved in a phase change
An amount of heat is added to ice, raising its temperature from -10 degrees Celsius to -5 degrees Celsius. A larger amount of heat is added to the same mass of liquid water, raising its temperature from 15 degrees Celsius to 20 degrees Celsius. From these results, we conclude that
the specific heat of ice is less than the specific heat of liquid water
When water boils in Denver, Colorado (elevation 5200 ft) its temperature is
less than the temperature of boiling water in Dallas, Texas (elevation 450 ft)
When the temperature of a quantity of gas is increased
the pressure and/or the volume must increase
The heat transfer process in which heat flows directly through the material is
conduction
The specific heat of liquid water is
one calorie per gram degree Celsius
When water is at its melting temperature
80 calories must be removed for each gram that is to be frozen
A heat engine
always rejects some heat to a lower temperature reservoir
The efficiency of a heat engine is given by the ratio of
net work done/amount of heat supplied
In an adiabatic process
no heat flows into or out of the system
It’s hot as blue blazes outside so you stand in front of your refrigerator with the door open to cool off. If you stand there long enough
the room will eventually get warmer
The average kinetic energy of the particles in a system is called
temperature
A heat engine takes in 500 J of energy from the hot reservoir in one cycle while performing 200 J of work. The amount of heat transferred to the cold reservoir in the same time is
300 J
Entropy is
a quantity that increases as the disorder of a system increases
An inventor has created a heat engine that extracts energy from geothermal hot spots and geysers like Old Faithful at Yellowstone National Park. She claims to turn all of the geothermal energy into work. Such a device is
a violation of Kelvin’s statement of the second law of thermodynamics
The efficiency of a Carnot engine would be increased if
he high and low temperatures were both lowered by 100 degrees Celsius
An amount of water forms a single hexagonally symmetric snowflake. Elsewhere the same amount of water is a droplet of liquid water. Which state has higher entropy?
The droplet of liquid water, since it is more unruly and can adopt almost any shape
what is the formula for pressure?
P= Force/Area
what is the basis of Pascal’s Principle?
Any change in the pressure of a fluid is transmitted uniformly in all directions throughout the fluid
define atmospheric pressure
the pressure of the layer of air that surrounds the earth
* decreases with altitude
who invented the barometer?
Torricelli
the viscosity of fluid is
a measure of the frictional effects within the fluid
the larger the viscosity …
the larger the frictional forces between different layers of the fluid
what is the zeroth law of thermodynamics
Two or more objects in thermal equilibrium have the same temperature
(thermal equilibrium is when the physical properties are no longer changing)
latent heat is
The amount of heat needed per unit mass to produce a phase change
In an isobaric process
the pressure of the gas remains constant
In an isothermal process
the temperature does not change
In conduction
heat flows through a material when objects at different temperatures are placed in contact with one another
In convection
heat is transferred by the motion of a fluid containing thermal energy
In radiation
heat energy is transferred by electromagnetic waves
Efficiency is
the ratio of the net work done by the engine to the amount of heat that must be supplied to accomplish this work
Carnot efficiency
is the maximum efficiency possible for any engine taking in heat from a reservoir at absolute temperature TH and releasing heat to a reservoir at temperature TC
The first law of thermodynamics
requires that, for a complete cycle, the heat released at the higher temperature must equal the energy put into the engine in the form of both heat and work
the second law of thermodynamics
Heat will not flow from a colder body to a hotter body unless some other process is also involved
When a glass rod rubbed with silk acquires a positive charge, the silk acquires…
a negative charge
A rod with a positive charge is brought near a positively charged pith ball. The pith ball is suspended from an insulating string. The pith ball will be…
repelled by the rod
If the distance between two point charges is doubled while the size of the charges remains the same, the force between the charges is multiplied by…
0.25
If the distance between two point charges remains constant while the size of one of the charges is doubled, the force between the charges is multiplied by…
2
Materials that allow electric charges to move freely are called…
conductors
The unit for electrical charge is…
Coulomb
Electric field lines are envisioned as…
radiating inward toward a negative charge and out of a positive charge
The normal tendency of positive charges is to…
move to regions of lower electric potential
The change in electric potential is equal to…
the change in electrostatic energy divided by the amount of the charge.
The unit for electric potential is…
volt
Electric current is…
the charge per unit time
The unit for electrical current is…
amperes
Electrical resistance is…
the property of a circuit element that opposes the flow of current
The unit of electrical resistance is…
ohms
Resistances connected in a series all have…
the same current
Resistances connected in parallel all have…
the same potential difference
Power supplied by a battery is calculated as…
the potential difference times the current
The power dissipated by a resistance may be calculated as…
the square of the current times the resistance.
A voltmeter is always connected…
in parallel with the circuit element whose potential difference is to be measured.
Household circuits are wired in…
parallel to a direct current source
The magnetic field lines produced by a current in a straight wire…
are directed in concentric circles around the wire.
Electrons flow around a circular wire loop in a horizontal plane, in a direction that is clockwise when viewed from above. This causes the magnetic field. Inside the loop, the direction of this magnetic field is…
down
The north pole of a magnetic compass needle points towards the north geographic pole of the earth because…
there is a south magnetic pole near the north geographic pole.
Which of the following cannot induce a current in a loop of wire? A. a stationary magnet inside the stationary loop. B. moving the loop near a magnet. C. moving a magnet near the loop. D. changing the current in nearby loop.
a stationary magnet inside the stationary loop.
A transformer is used to either increase or decrease the voltage in an AC circuit. When the output voltage is greater than the input voltage of a transformer then…
the power output is the same as the power input
Two long bar magnets are aligned so that north poles face each other. The magnets are separated by 1 cm, and a repulsive force between the north poles is 0.080 N. When the separation is increased to 2 cm the force will be…
0.020 N
Imagine a magnetic field pointing into the plane of this page (screen). An electron moves across the page (screen) from left to right. The direction of the magnetic force on the electron will be…
toward the bottom of the page (screen)
A transformer has 200 turns on the primary coil and 20 turns on the secondary coil. The primary coil is connected to a direct current source of 100 millivolts. The voltage in the secondary coil will be…
zero
High AC voltages are desirable for long distance transmission of electric power because…
the higher the voltage the lower the current, which reduces the power lost.
According to Faraday’s Law of Electromagnetic Induction the induced voltage is equal to…
the rate of change of the magnetic flux
The force between two unlike magnetic poles…
decreases as the square of the separation distance between them.
The magnetic field lines of a bar magnet…
emerge from the north pole and go into the south pole
If the distance between two point charges is tripled while the size of the charges remains the same, the force between the charges is multiplied by…
1/9
If the distance between two point charges remains constant while the size of each of the charges is quadrupled, the force between the charges is multiplied by…
16
Can you charge an object without actually touching it with another charged object..
Yes, this is an example of charging by induction
If the distance between two point charges remains constant while the size of one of the charges is quadrupled, the force between the charges is multiplied by…
4
The SI unit of magnetic field is the…
Telsa
Which of the following cannot induce a voltage in a loop of wire? A. Expanding or contracting the loop in a region where there is no magnetic field. B. moving the loop near a magnet. C. moving a magnet near the loop. D. changing the current in a nearby loop.
expanding or contracting the loop in a region where there is no magnetic field.
A generator has a coil of wire rotating in a magnetic field. If the rotation rate increases, how is the maximum output voltage of the generator affected?
the maximum voltage increases
A 6 V battery is connected to the primary coil of a transformer with 200 turns around the iron core. What is the voltage across the output terminals of the transformer if there are 400 turns on the secondary coil?
The output voltage is zero.
The primary coil of a cell phone charging transformer with 200 turns is plugged into the wall outlet (120 V) in a house in draws 0.1 A of current. What is the output charging current of the secondary coil of the transformer that has 20 turns?
The output current is greater than 0.1 A.
A horizontal wire carries a current straight toward you. From your point of view the magnetic field caused by this current…
circles the wire in a counterclockwise direction.
A current carrying circular loop of wire lies flat on the table top. When viewed from above, the current moves around the loop in a counterclockwise sense. What is the direction of the magnetic field inside the loop caused by this current?
The magnetic field points straight up
A current carrying circular loop of wire lies flat on a table top. When viewed from above, the current moves around the loop in a counterclockwise sense. what is the direction of the magnetic field outside the loop caused by this current?
magnetic field points straight down.
The location of maximum motion of a standing wave is
an antinode
The number of wave pulses per unit time is the
frequency of the wave
Which of the following is an example of longitudinal waves?
sound waves
The distance between the same points on successive pulses is the
wavelength of the wave
The time between successive wave pulses is the
period of the wave
A wave disturbance in which the displacement in the medium is parallel to the direction of wave travel is a
longitudinal wave
If you increase the tension of a string, the velocity of the wave on the string
increases
Water waves pass the end of a pier every four seconds. What is the frequency of the water waves?
0.25 Hz
A rowboat tied to a dock moves up and down with the water waves through a total distance of 40cm. The amplitude of the water waves is
20cm
A tuning fork for the “A” note vibrates with 440Hz. What is the frequency of the note that is one octave above the tuning fork?
880Hz