Question

Which of the following is an example of the first law of thermodynamics?

Options

• The specific heat of an object explains how easily it changes temperatures.

• While melting, an ice cube remains at the same temperature.

• When a refrigerator is unplugged, everything inside of it returns to room temperature after some time.

• After falling down the hill, a ball’s kinetic energy plus heat energy equals the initial potential energy.

Answer 1

After falling down the hill, a ball’s kinetic energy plus heat energy equals the initial potential energy.

Explanation:

There are three laws of thermodynamics. These laws explain the relationship between quantities such as heat, temperature, entropy, and work. The first law of thermodynamics defines that for the change in the internal energy, which becomes equal to the heat that adds to the system minus the work which is done by the system.

The expression obtained is, 

ΔU = Q – W

Here, ΔU is the change in internal energy.

Q is the heat added to the system.

W is the work done by the system.

The second law of thermodynamics defines that the total entropy in an isolated system will never decrease, and this is a constant only if all the process is reversible.

The third law of thermodynamics defines that the entropy in a system at the absolute zero temperature is a constant. Because the system here at zero temperature exists in the ground state.