Q- A household refrigerator that has a power input of 450W and a COP of 2.5 is to cool 5 large watermelons, 10 kg each, to 10^{o}C. If the melons are initially at 20^{o}C, determine how long it will take for the refrigerator to cool them. The specific heat of melons = 4.2 kJ/(kg.^{o}C)

## . : "Heat and Thermodynamics"

### Thermodynamics: Refrigerator

### Thermodynamics

Q- 15 kg of air in a piston cylinder device is heated inside the cylinder from 25^{0}C to 75^{0}C by passing current through a resistance heater inside the cylinder. The pressure inside the cylinder is kept constant at 2 bar during the process and the heat loss of 50 kJ occurs. Determine the electrical en…

### Heat Radiation

Q- A student is trying to decide what to wear. His bedroom is at 20.0 degrees Celsius. His skin temperature is 35.0 degrees Celsius. The area of his exposed skin is 1.50 m^{2}. People all over the world have skin that is dark in the infrared, with emissivity about 0.900. Find the net energy loss from h…

### Thermal Physics

Q- Work is done on the water by a rotating paddle wheel, which is driven by two blocks falling at a constant speed. The temperature of the stirred water increases due to friction between the water and the paddles. If the energy lost in the bearings and through the walls is neglected, then the loss i…

### Heat and Thermodynamics

Q- A spherical tank contains 1 mole of helium gas at 10 bar and 300 K. The gas is slowly released to the atmosphere in such a way the remaining gas is maintained at constant total energy U. Heating or cooling may be used to keep U constant during the venting. Helium behaves as an ideal gas with a co…

### Conduction Of Heat

Q- A glass windowpane has an area of 3.00 m^{2} and a thickness of 0.600 cm. If the temperature difference between its faces is 25.0 degrees Celsius, what is the rate of energy transfer by conduction through the window? (coefficient of conductivity for glass to be taken as 0.8 W/(m.K)

### Thermodynamics

Q- The initial state of 1.00 mol of a gas is *P _{1}* = 6.00 atm,

*V*= 5.00 L, and

_{1}*E*

_{int}_{ 1}= 790 J, The gas is allowed to expand at constant pressure to a volume of 9.00 L. It is then cooled at constant volume until its pressure is 4.00 atm and its final state becomes

*P*= 4.00 atm,

_{2}*V*= 9.00 L, and

_{2}*E*

_{int}_{ 2}

### Thermal physics

Q-(a) If the pressure of a gas is increased by a factor of 9, while its volume is held constant, by what factor does rms speed change?(b) In Joule’s experiment, the mass of the weights is 2.99 kg, and the insulated tank is filled with 0.137 g of water. What is the increase in the temperature of the …

## Comments

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