in today's video we're going to look at the conservation of energy principle which is one of the most important ideas in physics the principle itself is that energy can be transferred usefully stored or dissipated but can never be created or destroyed so basically we can't make new energy or destroy it it can only move between different objects and different forms now you don't need to worry about remembering any of these specific examples that we're going to use in today's video but you do need to understand the concept of conservation of energy and be able to apply it to different scenarios for example when you plug your phone into the wall to charge it electrical energy from the main supply in your house travels along the wire and gets transferred to the chemical energy store in your phone's battery then when you use your phone this chemical energy can be converted back to electrical energy which flows around the circuit in your phone and powers the different parts like the screen and the speaker in the screen the electrical energy will be converted to light energy so that you can see it and at the speaker will be converted to sound energy ideally every time their energy is transferred it would all be transferred usefully into the desired store that you wanted to go to in reality though some of it is going to be dissipated as wasted energy which just means to forms other than the one that we intended this wasted energy is generally in the form of heat which is why your phone might warm up a bit when it's charging or when you're using it a lot but remember that it can be in other forms too like sound energy the next thing we need to look at is the idea of open and closed systems now in physics a system is a bit of a weird term but it's basically just a portion of the physical universe that you've chosen to analyze and everything outside that system is known as the environment so in our phone example the phone could be considered the system and everything else in the universe would be the environment in this case we would say that the phone is an open system because energy and matter can freely move between the phone and the environment for example if your phone gets hot it gives out heat energy to the surroundings such as your skin on the other hand if we put your phone in a sealed jar then our system would be the entire contents of the jar including the phone and the air within the jar and we'll now call it a closed system because energy and matter can't answer or escape so this time when your phone heats up the heat energy will be dissipated to the air inside the jar so it stays within the system and importantly this means that the overall energy of a closed system doesn't ever change anyway that's all for today's video so if you enjoyed it then please do give us a like and subscribe and we'll see you next time