What is Heat?
Heat is not a thing, heat is a process.
Heat is the transfer of energy between two objects due to
temperature differences.
Notice that the name of the transfer process is heat. What
gets transferred is energy. Heat is NOT a substance although it is very
convenient to think of it that way. In fact, it used to be thought that heat
was a substance.
There is a circular nature to the definitions used:
(a) energy does work or produces heat, but
(b) heat is a transfer of energy.
Ultimately, energy is expressed in the motion of substances.
If it is moving, it has energy. If it has the capacity to move, there is some
potential energy stored away.
What is Clausius
statement?
It is impossible for a self-acting machine working in a
cyclic process, to transfer heat from a body at lower temperature to a body at
a higher temperature without the aid of an external agency.
What is Kelvin Planck
Statement?
It is impossible to construct a heat engine to produce
network in a complete cycle if it exchanges heat from a single reservoir at
single fixed temperature.
What is Heat engine?
Heat engine is a machine, which is used to convert the heat
energy into mechanical work in a cyclic process.
What are the
assumptions made on heat engine?
1. The source and sink are maintained at constant
temperature.
2. The source and sink has infinite heat capacity.
What is Heat pump?
A heat pump is a device, which is working in a cycle and
transfers heat from lower temperature to higher temperature.
What is Zeroth law of
Thermodynamics?
When two systems are separately in thermal equilibrium with
a third system then they themselves is in thermal equilibrium with each other.
What are the first
and second laws of thermodynamics?
The first law of thermodynamics says that energy cannot be
destroyed or created, only changed in form. The second law of thermodynamics
says that each time energy is converted from one form to another; some energy
is always lost as heat.
What is the term
internal energy?
Internal energy of a gas is the energy stored in a gas due
to its molecular interactions. It is also defined as the energy possessed by a
gas at a given temperature.
What is Energy?
The basic unit of energy is a Joule (J). Other units are calorie, kilo joule, British
Thermal Unit (BTU), and therm.
1000J = 1 kJ
1 BTU = 1.05 kJ
1 therm = 100,000 BTU
1000cal = 1kcal
1 cal = 4.184 J
Power: Power is the
rate at which energy is used.
(P = E/t) Unit: Watt
1 W = 1 J/s (1Watt = 1 Joule per second)
a) Kinetic energy is the energy of motion.
b) Potential energy is the energy stored in stressed
objects, like a bent bow or compressed spring, or water at the top of a
waterfall.
c) Chemical energy is the energy stored in chemical bonds,
which is released when a chemical reaction, like burning, occurs.
d) Nuclear energy is the energy stored within the nucleus of
an atom, which can be released under
certain conditions when the nucleus is made to break apart (fission), or when
two nuclei are forced together (fusion).