Exam 14: Temperature and Heat

If the surface temperature of the Earth is and that of the Sun is 6000 K, assuming the same emissivities, what is the ratio of the energy radiated per square meter of the Earth to that of the Sun?

The thermal conductivity of aluminum is 238 W / m · $\degree$ C and of copper is 397 W / m · $\degree$ C. A rod of each material is used as a heat conductor. If the rods have the same geometry and are used between the same temperature differences for the same time interval, what is the ratio of the heat transferred by the aluminum to the heat transferred by the copper?

Suppose working outside on a hot day someone generate 450 J of heat each second. If this energy is compensated for by the evaporation of sweat, how much water would be lost in an hour? The latent heat of fusion for water is 334 kJ/kg and for vaporization is 2,200 kJ/kg.

The filament temperature of a light bulb is 2000 K when the bulb delivers 50 W of power. If its emissivity remains constant, what power is delivered when the filament temperature is 2500 K?

A windowpane is half a centimeter thick and has an area of 2.0 m². The temperature difference between the inside and outside surfaces of the pane is 15 $\degree$ C. What is the rate of heat flow through this window? (Thermal conductivity for this glass is 0.84 W / m · $\degree$ C.)

As a copper wire is heated, its length increases by 0.200%. What is the change of the temperature of the wire? ( $\alpha$ _Cu = 16.6 *10 ^-6/C $\degree$ )

At what temperature is the same numerical value obtained in Celsius and Fahrenheit?

When a wool blanket is used to keep warm, what is the primary insulating material?

At room temperature, the coefficient of linear expansion for Pyrex glass is _____ that for ordinary glass.

I take 2.0 kg of ice and dump it into 1.0 kg of water and, when equilibrium is reached, I have 3.0 kg of ice at 0 $\degree$ C. The water was originally at 0 $\degree$ C. The specific heat of water = 1.00 kcal/kg· $\degree$ C, the specific heat of ice = 0.50 kcal/kg· $\degree$ C, and the latent heat of fusion of water is 80 kcal/kg. The original temperature of the ice was:

A rectangular steel plate with dimensions of 60 cm *25 cm is heated from 20 $\degree$ C to 150 $\degree$ C. What is its change in area? (Coefficient of linear expansion for steel is 11 *10 ^{- 6}/ $\degree$ C.)

Calories of the food type are equal to which of the following?

Arrange the following units, Calorie, calorie, and Joule from smallest to largest.

A 2.00-kg copper rod is 40.00 cm long at 23°C. If 50,000 J are transferred to the rod by heat, what is its change in length? (c_copper = 387 J/kg·°C and $\alpha$ _copper = 17 *10^-6/°C)

Between 0 $\degree$ C and 4 $\degree$ C, the volume coefficient of expansion for water:

Dmitri places one end of a copper rod in a heat reservoir and the other end in a heat sink. By what factor is the rate of heat flow changed when the temperature difference between the reservoir and sink is doubled?

An object at 27 $\degree$ C has its temperature increased to 47 $\degree$ C. The power then radiated by this object increases by how many percent?

At 20 $\degree$ C an aluminum ring has an inner diameter of 5.000 cm, and a brass rod has a diameter of 5.020 cm. Keeping the brass rod at 20°C, which of the following temperatures of the ring will allow the ring to just slip over the brass rod? ( $\alpha$ _Al = 2.4 *10 ^{- 5} / $\degree$ C, $\alpha$ _brass = 1.9 *10 ^{- 5}/ $\degree$ C )

The thermal expansion of a solid is caused by:

Marc attaches a falling 250-kg object with a rope through a pulley to a paddle wheel shaft. He places the system in a well-insulated tank holding 12 kg of water. When the object falls, it causes the paddle wheel to rotate and churn the water. If the object falls a vertical distance of 100 m at constant speed, what is the temperature change of the water? (1 kcal = 4186 J, the specific heat of water is 4186 J/kg · $\degree$ C, and g = 9.8 m/s²)