The SI unit of energy was named after him because of his significant contributions to the field of thermodynamics.
The internal energy of a system is changed by the addition or removal of heat.
A temperature increase is observed while cooking.
Adding heat doesn't increase the temperature.
When a substance changes from one phase to another, it's called melting ice.
The internal energy of the system can be changed by work done on the system.
Joule showed that the temperature of a system can be increased by stirring.
The work is done by the force of the rub against the rough surface.
We can't say that a system has a certain amount of heat or work.
The phrase "heat transfer" is used to emphasize its nature.
Two samples of the same substance are kept in a lab.
Someone adds 10 kJ of heat to one sample and 10 kJ of heat to another.
The internal energy of the substance can be changed by heat and work.
It is not possible to tell whether heat was added to sample A or B because the properties of the sample only depend on the internal energy.
One of the major effects of heat transfer is temperature change.
We assume that no work is done by the system and that there is no phase change.
The transfer of heat depends on three factors--the change in temperature, the mass of the system, and the substance and phase of the substance.
The magnitude of the temperature change, the mass of the system, and the substance and phase are some of the factors that affect the heat transfer to cause a temperature change.
To double the temperature change of a mass, you need to add more heat.
Adding twice the heat is needed to cause an equivalent temperature change in a doubled mass.
If it takes 10.8 times the amount of heat to cause a temperature change in a given mass of copper, it will take the same amount of heat to cause a temperature change in the same mass of water.
It is easy to understand the dependence on temperature change and mass.
The internal energy of a system is proportional to the absolute temperature and the number of atoms.
The heat needed to raise the temperature is less for alcohol than it is for water.
The phase of the substance affects the transfer of heat.
The amount of heat needed to change the temperature of 1.00 kg of mass is called the specific heat.
The temperature change in units of kelvin and degrees Celsius is the same.
There is no easy way to calculate the values of specific heat.
The heat depends on the temperature.
The temperature and volume dependence of the heat of most substances is weak.
The table shows that the specific heat of water is five times that of glass and ten times that of iron, which means that it takes five times as much heat to raise the temperature of water as it does for glass.
Water has one of the largest specific heats of any material, which is important for sustaining life on Earth.
A pan on a stove can heat 0.250 liters of water.
The pan and water are the same temperature.
The temperature of the water and the pan are the same when you put the pan on the stove.
The equation is used for the heat transfer for the mass of water and aluminum.
Table 14.1 has the heat values for water and aluminum.
The pan and water are at the same temperature because the water is in thermal contact with the aluminum.
The percentage of heat going into the pan was compared to the percentage of heat going into the water.
The amount of heat transferred to the container is a small fraction of the total heat.
The specific heat of water is four times greater than that of aluminum and the pan is twice the mass of the water.
It takes more than twice the heat to get the temperature change for the water as compared to the aluminum pan.
The mechanical equivalent of heat can be seen in the smoking brakes on this truck.
Truck brakes that are used to control speed on a downhill run work by converting potential energy into internal energy.
The conversion prevents the potential energy from being converted into the truck's energy.
The problem is that the mass of the truck is large compared with the brake material absorbing the energy, and the temperature increase may occur too fast for sufficient heat to transfer from the brakes to the environment.
If the brake material retains 10% of the energy from the truck descending 75.0 m at a constant speed, the temperature increase of 100 kilograms of brake material should be calculated.
If the brakes aren't applied, the potential energy is converted into energy.
The internal energy of the brake material is converted when brakes are applied.
We calculate the potential energy that the entire truck loses in its descent and then find the temperature increase in the brake material alone.
This idea underlies the recent hybrid technology of cars, where mechanical energy is converted by the brakes into electrical energy.
The values for liquids are at constant volume, except as noted.
A blow torch could be used to produce the temperature increase.
Suppose you put a pan of water off the stove with a temperature of.
If the pan is placed on an insulated pad, a small amount of water will boil off.
The pan is placed on an insulated pad so that there is little heat transfer.
The pan is at a higher temperature than the water.
Once the water and pan are in contact, heat transfer restores thermal equilibrium.
The mass of evaporated water is insignificant and the magnitude of the heat lost by the pan is equal to the heat gained by the water.
Once a thermal equilibrium between the pan and the water is achieved, the exchange of heat stops.