MEGA Elementary Education Multi-Content Practice Test

Which law of physics could disprove the claim of 100% efficiency in the car designed with an electric generator?

1. Newton's first law of motion

2. Newton's second law of motion

3. the first law of thermodynamics

4. the second law of thermodynamics

The correct answer is: the second law of thermodynamics

The second law of thermodynamics is fundamental in understanding energy efficiency, particularly in systems involving heat transfer and energy conversion. This law states that in any energy transfer or transformation, some energy is always lost as waste heat to the surroundings, leading to a decrease in the overall efficiency of the system. In the context of a car designed with an electric generator, claiming 100% efficiency implies that all the energy from the generator is converted into useful work with no losses. However, the second law of thermodynamics clearly establishes that this is impossible because some energy will invariably be transformed into thermal energy, which is not usable for work. Therefore, the claim of 100% efficiency contradicts the principles outlined in this law. Understanding this law is crucial, as it highlights the inherent limitations in all physical systems, ensuring that no system can convert energy completely without some expenditure of energy in the form of waste. This principle has important implications in engineering and energy use and reinforces the reality that achieving perfect efficiency in any mechanical system, including electric generators, is unattainable.