Question

Consider the following statements.
$1.$ A heat engine is a device which converts heat energy into mechanical energy.
$2.$ A heat engine essentially consists of source of heat at higher temperature, working substance and sink of heat at lower temperature.
$3.$ In a diesel engine, a mixture of fuel vapours and air acts as the working substance.
$4.$ Efficiency of a petrol engine is greater than diesel engine.
Which of the statements given above are correct?

• A. $1$ and $2$
• B. $1$ and $3$
• C. $1,2$ and $3$
• D. All of these

Answer 1

The correct option is C $1,2$ and $3$

1. Heat Engine absorbs heat from source to produce mechanical work and some residual heat to sink. $Q_{in}=Q_{out}+W$

2. The Heat source is at Higher temperature while sink is at the lower temperature. $\frac{Q_{in}}{T_{in}}=\frac{Q_{out}}{T_{out}}$

3. In diesel engine, fuel and vapors are mixed and together form the working substance.

4. Diesel engines are more efficient than the petrol engine, as diesel fuel is energy dense compared to the petrol.

S first three statements are correct, last is incorrect.