A carnot engine having an efficiency of $\frac{1}{10}$th of heat engine, is used as a refrigerator. If then work done on the system is 10 J, the amount of energy absorbed from the reservoir at lower temperature is:

1. 1 J

2. 90 J

3. 99 J

4. 100 J 

The temperature inside a refrigerator is ${t_2}^{\circ }C$and the room temperature is ${t_1}^{\circ }C$. The amount of heat delivered to the room for each joule of electrical energy consumed ideally will be:

1. $\frac{t_1}{t_1-t_2}$

2.  $\frac{t_1+273}{t_1-t_2}$

3. $\frac{t_2+273}{t_1+t_2}$

4.  $\frac{t_1+t_2}{t_1+273}$

The coefficient of performance of a refrigerator is 5. If the temperature inside freezer is -20°C, the temperature of the surroundings to which it rejects heat is  -

1. 31°C

2. 41°C

3. 11°C

4. 21°C

A Carnot engine working between 300 K and 600K has work output of 800 J per cycle. What is amount of heat energy supplied to the engine from source per cycle ?

(1) 1800 J/cycle

(2) 1000 J/cycle

(3) 2000 J/cycle

(4) 1600 J/cycle

A Carnot's engine used first an ideal monoatomic gas then an ideal diatomic gas. If the source and sink temperature are 411°C and 69°C respectively and the engine extracts 1000 J of heat in each cycle, then area enclosed by the PV diagram is -

(1) 100 J

(2) 300 J

(3) 500 J

(4) 700 J