 You probably all have already experienced some static electricity for example when taking off pullover or going off a car and then touching some objects and suddenly get sent. But what is actually going on? In this video I'm going to give you the basics of electrostatics. In earlier videos we have already talked about anions being negatively charged and captions being positively charged. Now these principles of if you have more electrons than protons or less protons than electrons that can lead to no real charge can not only apply to individual atoms but to entire objects. So if an object is positively charged it has more protons than electrons and if it's negatively charged more electrons than protons. Now at this point you might want to point out what is the charge of a proton? What is the charge of an electron? Now a proton is charged plus one elementary charge while the electron is charged minus one elementary charge. And what is an elementary charge it is 1.6 times 10 to minus 19 coulomb. So a very small value in the units of coulomb. As our overall charge is made of the difference of the protons and electrons our charge is quantized. What does this mean? This means we cannot just have any value. Our charge has to be a multiple of the elementary charge. It is impossible to charge an object let's say to 1.3 times 10 to minus 19 coulombs because that would mean we would split an electron or a proton in parts. We can only have a full proton or a full electrons we cannot have anything in between. So charge is quantized and the overall charge will be the number of excess protons times the elementary charge or the number of excess electrons times the elementary charge. So now how do we charge an object? There are three main ways to charge an object. Number one is conduction. You bring a charged object into contact with another one and some electrons simply jump from one onto the other so we can charge something by contact. The next option is by friction. This is exactly happening when you take your pullover off or when you put a comp through your hair you're charging an object by friction. How is that happening? Not all substances want electrons as much as others. Some are more electron negative so they will try to take electrons from something else. So if we bring two substances in contact that have a different electronegativity let's say this hand wants the electron more where there is a contact to another substance it will temporarily take over some electrons from the molecules in the surface of the other substance. So when I break up the contact then the electrons will stay on one side and the one that's more electronegative will become negatively charged and the other object will become positively charged. Of course with two hands like this it wouldn't happen because they're made of the same material so I need two different materials for example this material here and the hand or a plastic comb and my hair. Now instead of just going into contact and ripping off the contact constantly what I can also do I can do friction because with friction if you would look very closely you would very often create the contact and break it up again create the contact break it up again and so on and so on. So friction is a very efficient way to charge an object and then the next one is charging an object by induction without even touching it. So what is happening so let's say I have an object so let's say I have an object that is charged and I bring it close to a non-charged object. If the electrons can move in this object that will happen the electrons will get attracted to the positive charge while the positive charges get repelled so each side of that object now would have an induced charge and now could for example connect this to ground and let more electrons come in through here to counteract my my excess positive charge and then if I take off the connection to ground my second object will be negatively charged. This can also happen just on the molecular level. A water molecule for example has a slightly positive side and a slightly negative side so a water molecule can simply reorientate itself towards the charge and so that the negative side is facing the charge and then be attracted to it like that. How can we use this we can do some experiments at home for example you can rub a balloon against your hair to make the balloon charged and then when you bring it close to the wall the charges inside the molecules of the wall will reorientate themselves so that the charge opposing the charge of the balloon is slightly closer and therefore overall cause an attraction between the balloon and the wall and the balloon will stay on the wall. Another experiment is you can use a comb charge it by going through your hair with it and then bring it close to water and you will see that the water molecules will reorientate themselves so that the opposing charge is closer to the comb therefore overall the attraction will win over the repulsion and the water stream that's falling down from your faucet will get slightly bent around your comb. Now after we have talked how an object can get charged let's look how charge can be conducted through an object. Now what does it mean for an object to be a conductor it means that there is some charge that can move freely could be either the three electrons in the case of metals or ions in a solution so for example with my plug here the metal is the part that is conducting electricity. Now what's the opposite of a conductor is an insulator which is a material that does not allow charge to flow freely for example the plastic on my plug here is made of an insulating material because I don't want the charge to go from the metal through the plastic into my hand. And last but not least we have these interesting materials which are called semiconductors which under certain circumstances can act like a conductor and then under other circumstances can act like an insulator. Why are they so important because we can basically use them to build a switch if they act like the insulator the switch is open so no current will be passing through that wire if however they can be made to act like a conductor which happens if I apply an electric field perpendicular to them then they will let current pass so we can build tiny tiny switches that we can turn easily on and off by applying an electric field up and down and with these little switches we build our computers our cell phones and all our little electronic gadgets that are doing some computations for us.