Energy Physics: Forms and Interactions

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Questions and Answers

A refrigerator uses $100 J$ of electrical energy to remove $300 J$ of heat from its interior. What is the coefficient of performance (COP) of the refrigerator?

3.0 (correct)
2.0
0.33
4.0

Which of the following scenarios best illustrates the principles of the Second Law of Thermodynamics regarding entropy in a closed system?

Refrigerating food to keep it fresh and prevent it from spoiling.
Ice melting in a glass of water until thermal equilibrium is reached. (correct)
A plant converting sunlight into glucose through photosynthesis.
Organizing a messy room so that items are neatly arranged.

A coal-fired power plant has an overall efficiency of 35% in converting the chemical energy of coal into electrical energy. What happens to the remaining 65% of the energy?

It is converted into kinetic energy to power the turbines.
It is stored in batteries for later use.
It is transformed into nuclear energy.
It is lost as waste heat to the environment. (correct)

A new technology claims to convert heat entirely into work with 100% efficiency. According to the laws of thermodynamics, what is the most likely reason this claim is false?

The technology violates the Second Law of Thermodynamics by creating a perpetual motion. (C) Signup and view all the answers

A wind turbine generates electricity with an efficiency of 40%. If the wind turbine captures $5000 J$ of kinetic energy from the wind per second, how much electrical energy does it produce per second?

$2,000 J$ (B) Signup and view all the answers

A car with a mass of 1000 kg accelerates from rest to 20 m/s. How much work is required to increase the car's kinetic energy by this much?

<ol> <li>0 x 10^5 J (B)</li> </ol> Signup and view all the answers

In a closed system, a 2 kg object is raised 5 meters above the ground. By how much does the object's potential energy change?

98.1 J (A) Signup and view all the answers

Which of the following statements accurately describes the relationship between heat, work, and internal energy as defined in the first law of thermodynamics?

The change in internal energy is equal to the heat added to the system minus the work done by the system (A) Signup and view all the answers

A heat engine operates between two reservoirs at temperatures of 500 K and 300 K. What is the maximum possible efficiency of this engine?

40% (D) Signup and view all the answers

During a phase transition, such as melting ice, what happens to the temperature of the substance while heat is being added?

The temperature remains constant (B) Signup and view all the answers

Which of the following best exemplifies heat transfer via convection?

The circulation of hot air in a room (C) Signup and view all the answers

A solar panel converts light energy into electrical energy with an efficiency of 20%. If the solar panel receives 500 J of light energy, how much electrical energy does it produce?

100 J (C) Signup and view all the answers

Which of the following is a primary advantage of using renewable energy sources over fossil fuels?

Reduced greenhouse gas emissions (D) Signup and view all the answers

In nuclear fission, a neutron strikes a Uranium-235 nucleus, causing it to split. What is the immediate outcome of this reaction?

The release of energy and more neutrons (A) Signup and view all the answers

What is the energy of a photon of blue light with a frequency of $6.0 \times 10^{14}$ Hz?

$3.98 \times 10^{-19}$ J (A) Signup and view all the answers

Which of the following applications primarily relies on the principles of energy transfer and conversion for its functionality?

A combustion engine propelling a car (C) Signup and view all the answers

In the context of energy physics, what is the significance of entropy as described by the second law of thermodynamics?

Entropy measures the degree of disorder or randomness in a system (D) Signup and view all the answers

Which of the following statements is a correct application of the Zeroth Law of Thermodynamics?

If two systems are each in thermal equilibrium with a third, they are in thermal equilibrium with each other. (B) Signup and view all the answers

How does the concept of mass-energy equivalence, described by (E = mc^2), relate to nuclear reactions?

It demonstrates how a small amount of mass can be converted into a substantial amount of energy. (A) Signup and view all the answers

Which of the following energy sources relies on the conversion of kinetic energy into electrical energy through electromagnetic induction?

Wind turbines (C) Signup and view all the answers

Flashcards

Efficiency (η)

Ratio of useful energy output to total energy input. Always less than 1 (or 100%)

Power

Rate at which energy is transferred or converted, measured in watts (W).