19 Thermal Physics Flashcards
Thermal energy
Internal energy of an object due to temperature
Internal energy increase
Energy transfer by heating the object
Work done on the object
Internal energy of an object stays constant
No energy transfer
The energy transfer by heating and work done balance each other out
First law of thermodynamics
The change of internal energy of the object = the total energy transfer due to work dine and heating
Molecules in a solid
Atoms and molecules are held to each other by force due to the electrical charges of the protons and electrons in the atoms. The molecules vibrate randomly about a fixed point. The energy supplied by heating provides enough potential energy of the molecules because they break free from each other
Molecules in liquid
Molecules move around randomly, the forces between molecules are not strong enough to hold the molecules in position
Molecules in a gas
Molecules also move about randomly but much further apart on average than in a liquid. Heating a gas or a vapour makes the molecules speed up and so gain kinetic energy
Internal energy
The internal energy of an object is the sum of the random distribution of the kinetic and potential energies of its molecules
Thermal equilibrium
When no overall heat transfer occurs between two objects at the same temperture
Absolute scale
Temperature scale in kelvins defined in terms of absolute zero
Absolute zero
The lowest possible temperature, the temperature at which an object has minimum internal energy
Temperature rise of an object
Mass of the object
Amount of energy supplied to it
Substance from which the object is made
Specific heat capacity
Substance if energy needed to raise the temperature of unit mass of the substance by 1K without state change
E= mc🔺T
Inversion tube experiment
The gradational potential energy if an object falling in a tube is converted into internal energy when it hits the bottom of the tube.
Tube is inverted each time the spheres hit the bottom of the tube. The temperature of the lead shot is measured initially and after a particular number of inversions
Inversion tube experiment (equations)
Loss of gravitational potential energy for each inversion =mgL
N inversions, loss of gravitational potential energy = mgLN
C = gLn / 🔺T
