A Heat engine is a device which converts heat energy into mechanical energy. Efficiency of heat engine is the fraction of total heat supplied to the engine, which is converted into work.
A Carnot engine is an ideal heat engine, which consists of a source of infinite thermal capacity maintained at a constant temperature and a sink of heat of infinite thermal capacity maintained at constant low temperature. An ideal gas acts as the working substance. It is contained in a cylinder fitted with an insulating frictionless position. The cylinder has a conducting base and insulating walls. It can be placed on an insulating pad.
Sublimation is the process of conversion of certain solids directly to gaseous state on heating.On being cooled; the vapours get converted back into solids. Condensation is the process of conversion of gases/vapours to liquid state on cooling. On heating these liquids are converted into vapours/gases.
When a wire carrying weights at both its ends is suspended on a block of ice, the wire cuts the ice block and moves down, but the ice block gets intact above the wire. This process is known as regelation. In this process, when pressure on ice increased, the melting point of ice decreases, and ice melts. Therefore the wire penetrates into the block. Once the pressure on ice is removed, melting point of ice increases and the melted ice gets frozen and the block becomes intact.
Thermal conduction is the process in which particle of the body at higher temperature transmit heat of the particle at lower temperature by mutual contact only and not by any movement of the particle. All solids are heated by conduction.
Thermal convection is the phenomenon of transfer of heat by actual mass motion of the medium. All liquids and gasses are heated by convection. Most of the heat transfer that is taking place on earth is by convection. Contribution due to conduction and radiation is very small.
Radiation is the phenomenon of transfer of heat from source or receiver and without heating the intervening medium. For example, heat comes to us from the sum through radiation.