There is a large magnet and a small magnet on a smooth table surface. The large magnet is slowly moved closer to the smaller magnet until the magnetic field causes the small magnet to slide across the table and hit the large magnet. Where did the energy come from to move the small magnet? I know that energy cannot be created or destroyed but instead converted from one form into another. So energy was taken from one source and converted to some kind of work energy to move the magnet. Where was the energy taken from? What energy source has been depleted?
In: 1
There is a ball at the top of a hill. It is slowly pushed until it suddenly starts rolling, and hits the bottom of the hill. Where did the energy come from to move that ball down the hill?
That’s the same question, and the answer to both is that the absolute amount of energy actually isn’t really part of the system.
The only thing that matters is the difference between your starting point and your ending point. You started with us having a high potential energy system, and that potential energy was turned into kinetic energy when the magnet moved. The same way, I started with a high potential energy system with a ball on the top of a hill.
The energy that was used moving the magnet could have come from any number of places, and not all of them would have been “just one action”, because the world is messy, and we know all of the interactions that happen. So we define energy based on the difference between the highest point in the system and the lowest point.
[removed]
The magnets create a magnetic field and always attract/repel each other. Between any two magnets anywhere in the universe, you can calculate the potential energy they have between them. It’s no different than two electrically charged objects attracting/repelling each other or two objects with mass attracting each other gravitational. By simply being an object that interacts with a magnetic field, it has a potential energy in that magnetic field.
Latest Answers