What is an example the first law of thermodynamics?

Answer 1

Our Bodies Convert Concetrated Energy to Useless Low-Grade Energy

Animals, plants, and humans, use energy changes to move, grow, catch food, and make more of themselves. Cellular respiration is the process by which most living things convert concentrated food energy into work and thermal energy (often called heat), just as car and truck engines convert fuel energy into work and thermal energy (still often called heat). Our bodies do this by controlling complex chemical reactions in which concentrated energy is carefully moved from higher molecular bond energy levels to lower molecular bond energies. On the way, some of the energy (not all) is captured by ATP molecules and used by our cells to do the useful things described above.

When you exercise, some of the food energy gets converted into muscle work, but most of it gets converted to what we engineers call low-grade thermal energy. That's why you get all hot and sweaty. In fact, more than 60% of the food energy is converted to body-warming sweat-making thermal energy during metabolism of food energy. That leaves only 40% to do useful work in the cells. If you also figure in the energy required to digest the food and to pump it around in blood to all the cells, the final number can be significantly less than 40%. That's about the same as many of our human-made engines.

And, as with human-made machines and devices, all of the mechanical work done by the cells also ends up as low-grade heat (thermal energy), lost to us forever. The total amount of energy hasn't changed (1st law), but we can't use it anymore (2nd Law).

Answer 2

Any process in which energy is transformed - or even where energy is simply stored. Energy is always conserved, so basically you can't find a counterexample.

Consider, as an example, a falling object. Potential energy (energy of position) is converted to kinetic energy (movement energy). Once it crashes on the ground, this kinetic energy is converted to heat. In the entire process, no energy is created or destroyed - it is simply converted from one form to another.

Answer 3

My personal favorite is dropping an ice cube into a warm drink to cool it down. Now thermodynamics tells us that the ice provides a pathway by which the drink can loose energy, the very energy that is currently keeping it warm. The ice doesn't cool the drink but rather the drink heats up the ice, providing more liquid in the container per unit volume and thus a cooler drink after the ice is completely melted. Just remember, energy is transferable and heat is the physical manifestation of energy that simply allows out seances to detect its presence. Other examples could include you going into a pool to cool off, air conditioners is a great example.

Answer 4

It can be said that anything is an example, since the Law of Conservation of Energy has never found to be violated.

For more specific examples, think about some energy transformations, and try to understand where the energy went. Usually, most wasted energy will be converted to heat.

Answer 5

Power stations :) pumps, hair dryers anything which is a system really

Answer 6

The second law of thermodynamics states that entropy increases. The fact that we cannot build a perpetual motion machine, is one example.

Answer 7

Gas in a piston-cylinder arrangement