physics chapter 18
object A with heat capacity Ca and initially at temperature Ta is placed in thermal contact with object B, with heat capacity Cb and initially at temperature Tb. the combination is thermally isolated. if the heat capacities are independent of the temperature and no phase changes occur, the final temperature of both objects is
(CaTa+CbTb)/(Ca+Cb)
solid A with mass M is at its melting point Ta it is placed in thermal contact with solid B with heat capacity Cb and initially at temperature Tb(Tb>Ta) the combination is thermally isolated. A has latent heat of fusion L and when it has melted has heat capacity Ca. if A completely melts the final temperature of both A and B is
(CaTa+CbTb-ML)/(Ca+Cb)
possible units for the coefficient of volume expansion are
1/degrees C
a system undergoes an adiabatic process in which its internal energy increases by 20J. which of the following statements is true
20J of work was done on the system
the air temperature on a summer day might be
25degrees C
A kelvin thermometer and a Fahrenheit thermometer both give the same reading for a certain sample. the corresponding Celsius temperature is
301degrees C
a calorie is about
4.2J
Fahrenheit and Kelvin scales agree numerically at a reading of
574
Room temperature is about 20 degrees on the
Celsius scale
pressure versus volume graphs for a certain gas undergoing five different cyclic processes are shown below. during which cycle does the gas do the greatest positive work
D
a metal sample of mass M requires a power input P to just remain molten. when the heater is turned off, the metal solidifies in a time T. The specific latent heat of fusion of this metal is
PT/M
the rate of heat flow by conduction through a slab is Pcond if the slab thickness is doubled its cross-sectional area is halved and the temperature difference across it is doubled then the rate of heat flow becomes
Pcond/2
the diagram shows four thermometers labeled W,X,Y,Z. the freezing and boiling points of water are indicated. Rank the thermometers according to the size of a degree on their scales, smallest to largest
Z,X,W,Y
the formation of ice from water is accompanied by
absorption of energy as heat
the figure shows a rectangular brass plate at 0degrees C in which there is a cut rectangular hole of dimensions indicated. if the temperature of the plate is raised to 150degrees C
both x and y will increase
the unit of thermal conductivity might be
cal/(cm*s*Cdegree)
the two metallic strips that constitute some thermostats must differ in
coefficients of linear expansion
heat is
energy transferred by virtue of a temperature difference
there is a temperature which the reading on the Kelvin scale is numerically
equal to that on the Fahrenheit scale
according to the first law of thermodynamics applied to a gas the increase in the internal energy during any process
equals the heat input plus the work done on the gas
two different samples have the same mass and temperature. equal quantities of energy are absorbed as heat by each. their final temperatures may be different because the samples have different
heat capacities
a thermometer indicates 98degrees C. it may be
in a cup of hot tea
thin strips of iron and zinc are riveted together to form a bimetallic strip that bends when heated. The iron is on the inside of the bend because
it has a lower coefficient of linear expression
a balloon is filled with cold air and placed in a warm room. it is NOT in thermal equilibrium with the air of the room until
it stops expanding
an iron stove used for heating a room by radiation is more efficient if
its outer surface is rough and black
a slab of material has area A, thickness L, and thermal conductivity k. one of its surfaces(P) is maintained at temperature T1 and the other surface (Q) is maintained at a lower temperature T2 the rate of heat flow by conduction from P to Q is
kA(T1-T2)/L
an insulated container filled with water contains a thermometer and a paddle wheel. the paddle wheel can be rotated by an external source. this apparatus can be used to determine
mechanical equivalent of heat
the heat of fusion of water is cal/g. this means 80 can of energy are required to
melt 1g of ice
inside a room at a uniform comfortable temperature, metallic objects generally feel cooler to the touch than wooden objects do. this is because
metal conducts heat better than wood
a thermos bottle works well because
none of the above
the mercury column in an ordinary medical thermometer doubles in length when its temperature changes from 95degrees F to 105degrees F. choose the correct statement
none of the above are true
the international standard thermometer is kept
nowhere
when two gases separated by a diathermal wall are in thermal equilibrium with each other
only their temperatures must be the same
the help keep buildings cool in the summer, dark colored window shades have been replaced by light color shades. this is because light colored shades
reflect more sunlight
the triple point of a substance is that point for which the temperature and pressure are such that
solid, liquid, and vapor are all in equilibrium
the rate of heat flow by conduction through a slab does NOT depend upon the
specific heat of the slab
on a very cold day, a child puts his tongue against a fence post. it is much more likely that his tongue will stick to the steel post than to a wooden post. this is because
steel is a better heat conductor
if the zeroth law of thermodynamics were not valid, which of the following could not be considered a property of an object
temperature
which of the following statements is true
temperatures which differ by 10degrees on the Celsius scale but differ by 18degrees on the Fahrenheit scale
the zeroth law of thermodynamics allows us to define
termperature
suppose object c is in thermal equilibrium with object A and with object B. the zeroth law of thermodynamics states
that A is in thermal equilibrium with B
the specific heat of a substance is
the amount of heat energy per unit mass to raise the temperature of the substance by 1 degree C
the heat capacity of an object is
the amount of heat energy that raises its temperature by 1 degree C
an annular ring of aluminum is cut from an aluminum sheet as shown. when this ring is heated
the area of the hole expands the same percent as any area of the aluminum
it is more difficult to measure the coefficient of volume expansion of a liquid than that of a solid because
the containing vessel also expands
of the following which might NOT vanish over one cycle of a cyclic process
the energy absorbed by the substance as heat
a heat of transformation of a substance is
the energy per unit mass absorbed as heat during a phase transformation
in a certain process a gas ends in its original thermodynamics state. of the following which is possible as the net result of the process
the gas absorbs 50J of energy as heat and does 50J of work
constant-volume gas thermometers using different gases all indicate nearly the same temperature when in contact with the same object if
the particle concentrations are all extremely small
the heat capacity at constant volume and the heat capacity at constant pressure have different values because
the system does work at constant pressure but not at constant volume
during the time that latent heat is involved in a change of state
the temperature does not change
the same energy Q enters five different substances as heat. which substance has the greatest specific heat
the temperature of 4g of substance B increases by 4K
for constant -volume processes the heat capacity of gas A is greater than the heat capacity of gas B. We conclude that when they both absorb the same energy as heat at constant volume
the temperature of B increases more than the temperature of A
the diagram shows four rectangular plates and their dimensions. all are made of the same material. the temperature now increases. of these plates
the vertical dimension of plate 4 increases the most and the area of plate 3 increases the most
in an adiabatic process
the work done by the environment on the system equals the change in internal energy
of the following which might NOT vanish over one cycle of a cyclic process
the work done by the substance
if two objects are in thermal equilibrium with each other
they cannot be at different temperatures
in constructing a thermometer it is NECESSARY to use a substance that
undergoes some change when heated or cooled
which of the following statements pertaining to a vacuum flask(thermos) is not correct
vacuum reduces radiation loss
metal pipes, used to carry water, sometimes burst in the winter because
water expands when it freezes
a gram of distilled water at 4degrees C
will decrease slightly in volume when heated to 6degrees C
heat has the same units as
work
