The coefficient of performance of an ideal refrigerator is 3 which extracts heat from the sink at the rate of 399 J per cycle. The amount of heat it gives to the room per cycle will be:

1 532 J

2 250 J

3 300 J

4 496 J

If a refrigerator extracts heat 'a' from the cold reservoir and 'b' is the heat released from the hot reservoir, then the work done on the refrigerant (system) is:

1. a + b

2. $\mathrm{a}-\mathrm{b}$

3. a

4. $\mathrm{b}-\mathrm{a}$

A refrigerator whose coefficient of performance is 5 extracts heat from the cooling chamber at a rate of 250 J per cycle. For refrigeration, the work done per cycle is:

1. 150 J

2. 200 J

3. 100 J

4. 50 J

An ideal refrigerator has a freezer at a temperature of –13°C . The coefficient of performance of the engine is 5. The temperature of the air (at which heat is rejected) will be 
1. 325°C
2. 325K
3. 39°C
4. 320°C

A steam engine delivers \(5.4\times 10^8\) J of work per minute and extracts \(3.6\times 10^9\) J of heat per minute from its boiler. The efficiency of the engine is:
1. \(15\%\)
2. \(18\%\)
3. \(13\%\)
4. \(11\%\)

A refrigerator is to maintain eatables kept inside at \(9^\circ \text{C}.\) If room temperature is \(36^\circ \text{C},\) the coefficient of performance is:
1. \(9.3\)
2. \(12.4\)
3. \(11.2\)
4. \(10.4\)

Consider a heat engine as shown in the figure. ${\mathrm{Q}}_1<mspace\; width="1em"></mspace>\mathrm{and}<mspace\; width="1em"></mspace>{\mathrm{Q}}_2$ are heat added to ${\mathrm{T}}_1$ and heat taken from ${\mathrm{T}}_2$ respectively, in one cycle of the engine. W is the mechanical work done on the engine.

If W > 0, then possibilities are:

$(a)<mspace\; width="1em"></mspace>{\mathrm{Q}}_1>{\mathrm{Q}}_2>0(b)<mspace\; width="1em"></mspace>{\mathrm{Q}}_2>{\mathrm{Q}}_1>0(c)<mspace\; width="1em"></mspace>{\mathrm{Q}}_2<{\mathrm{Q}}_1<0(d)<mspace\; width="1em"></mspace>{\mathrm{Q}}_1<0,<mspace\; width="1em"></mspace>{\mathrm{Q}}_2>0$

Choose the correct alternatives:
1. (b, c)

2. (a, d)

3. (b, d)

4. (a, c)

An engine has an efficiency of $\frac{1}{6}$. When the temperature of the sink is reduced by ${62}^{0}C$, its efficiency is doubled. the temperature of the source is:

1. 124^oC

2. 37^oC

3. 62^oC

4. 99^oC

A Carnot engine, having an efficiency of $\mathrm{\eta }$ = $\frac{1}{10}$ as a heat engine, is used as a refrigerator. If the work done on the system is \(10\) J, the amount of energy absorbed from the reservoir at a lower temperature is:
1. \(100\) J
2. \(99\) J
3. \(90\) J
4. \(1\) J