Thermal Physics Flashcards
Energy transfer takes place by heating in what situation?
If there’s a temp difference.
What is internal energy?
What is it due to?
Sum of randomly distributed kinetic energies and potential energies of the particles.
Internal energy of an object is the energy of the molecules due to their individual movements and positions.
The internal energy of an object due to its temperature is called?
Thermal energy
Internal energy of an object increases for what two reasons?
-energy transfer by heating the object, or
-work done on the object eg work done by electricity.
If internal energy stays constant, then either..? (2)
-there’s no energy transfer by heating and no work done, or
-energy transfer by heating and work done balance each other out.
What’s the first law of thermodynamics?
When work is done on or by an object and/or energy is transferred by heating:
the change of internal energy of object = total energy transferred due to work done and heating.
ΔU = Q - W
What is a molecule?
The smallest particle of a pure substance that is characteristic of the substance eg H2O
What is an atom?
The smallest part of an element that is characteristic of the element eg H
What is internal energy of an object (relate two energies)?
The sum of the random distributions of the kinetic and potential energies of its molecules.
What’s thermal eqm?
When two objects are at the same temperature; no overall energy transfer by heating will take place.
What is absolute zero?
The lowest temperature possible. Objects at 0K have minimum internal energy.
Define specific heat capacity.
The energy needed to raise the temp of unit mass of the substance by 1K without change of state.
ΔQ = mcΔT
Measuring SHC of metal:
electric heater purpose?
water in hole purpose?
equation?
Electrical heater used to heat metal by supplying measured amount of electrical energy.
Water to improve thermal contact between metal and thermometer.
E supplied = V x I x t
∴ IVt = mcΔT
Measuring SHC of liquid:
apparatus name?
equation?
Liquid in calorimeter
E =IVt
Q(l) = m(l) x c(l) x ΔT
Q(cal) = m(cal) x c(cal) x ΔT
IVt= m(l) c(l) ΔT + m(cal) c(cal) ΔT
Continuous flow heating:
For a mass, m of liquid passing through the heater in time, t at a steady flow rate, and assuming no heat loss, what’s the eq that links power and shc?
Give two examples of continuous flow heating.
IV = mcΔT/t
Eg electric shower, solar heating panel.
Note: if volume flow rate given, need density to find rate of flow of mass (m/t)
