Which statement best describes how energy is conserved according to the law of conservation of energy?

• A. Energy is always lost as heat and cannot be recovered in any process.
• B. The total energy of an isolated system remains constant; $E=\mathrm{constant}$; energy can change forms but cannot be created or destroyed.
• C. The total energy of a system increases over time as work is done.
• D. Energy can be created from nothing if the system is closed.

Answer: (B)

Verified step by step guidance

1. Understand the law of conservation of energy, which states that energy cannot be created or destroyed in an isolated system; it can only change from one form to another.
2. Recognize that the total energy \(E\) of an isolated system remains constant over time, which can be expressed mathematically as \(E = \text{constant}\).
3. Note that while energy can transform between kinetic, potential, thermal, chemical, and other forms, the sum of all these energies in the system does not change.
4. Identify that energy losses, such as heat, are not truly lost but rather transferred or transformed within the system or to the surroundings, maintaining the total energy balance.
5. Conclude that any statement claiming energy is created from nothing or that total energy increases or is irrecoverably lost contradicts the fundamental principle of energy conservation.