What is a heat engine?

What is heat engine? Explain the principle and working of a heat engine. Define its efficiency.

What is the value of the efficiency of an ideal heat engine?

What is a heat reservoir? What is its heat capacity?

The efficiency of an ideal heat engine is

The efficiency of an ideal heat engine working between the freezing point and boilling point of water, is

The efficiency of an ideal heat engine working between the freezing point and boiling point of water, is

What is solar heating device?