[Music] hello dan dolkovsky here from howtomechatronics.com in this video we will learn what electric charge is and how electricity works to understand electricity we need to start with the atom matter is made of atoms we are made of atoms everything in the universe is made of atoms an atom cannot be seen with a naked eye so we will use a simplified model which can help us understand the structure of the atom this is called the bohr model in the center of the atom there is a nucleus which consists of neutrons which have no charge and protons which have positive charge also there are negatively charged electrons orbiting around the nucleus the number of neutrons protons and electrons an atom has can tell us which material it is the protons in the neutrons are positioned in the center of the atom while the electrons circulate around the nucleus in a constant motion the electrons are much lighter than the protons in the nucleus and they can move very easily with almost the speed of light they move around the nucleus in circular orbits or shells each shell can contain only a particular number of electrons the first shell can hold two electrons the second shell eight electrons the third shell can hold up to 18 and so on the shells are filled up with electrons from the inside out the number of electrons in the last outer shell determines the reactivity of the atom or its tendency to form chemical bonds with other atoms when that shell is full the atom is stable and least reactive the outer shell is known as the valence shell or the electrons found in it are called valence electrons some materials in this shell have loosely bounced electrons which allows them to flow from one atom to another these moving electrons are called free electrons how easy it is for electron to move around depends on the material materials can be either conductors or insulators materials that are conductors like most metals allows free electrons to move freely throughout the solid while insulators like plastic or glass limit the movement of the electrons holding them tightly generally the atoms have neutral charge which means that they have the same number of electrons and protons in other words they have a net electric charge equal to zero this is the lowest possible energy level of the atom or so-called the ground state however we can change the atom's charge by causing it to gain or lose electrons if an atom gains electrons it becomes negatively charged and opposite if the atom loses electrons it becomes positively charged charge atom is called positive or negative ion for example when you drag your feet across a carpet you are creating many surface contacts between your feet and the carpet allowing electrons to transfer to you thereby building a static charge on your skin instead of you and the carpet having a neutral charge a charge imbalance is being created between you as a conductor and the carpet as an insulator then for example when you touch a doorknob which is a metal all the charge wants to leave you and go to the doorknob in order to restore the charge imbalance therefore you get a shock as the electrons leave you nature always seeks balance a neutral charge equilibrium or a net charge of zero during this process we didn't create any new charges the overall charge between the objects is still zero this leads us to the law of conservation of electric charge which says that you can't create a net electric charge instead charge can only move from one place to another electric charge in fact is the most important property of the protons and electrons the charge is denoted by q and the unit of charge is coulomb objects can be positively or negatively charged hence q can have both positive and negative values the charge of a single electron or proton is known as elementary charge and is denoted with the lowercase e protons have a charge of positive e and electrons of negative e so one electron has a charge of negative 1.6 times 10 to the negative 19 coulomb and one negative coulomb has 6.24 times 10 to the 18th electrons one proton has the same value of electric charge but with positive sign the flow of electrons is what forms an electric current if we look inside a piece of a copper wire there are atoms that easily exchange electrons these electrons are able to move from one atom to another in any direction if we make a closed circuit by connecting the copper wire with a power source like a battery then the voltage will make the electrons to move in the same direction from one terminal of the battery to the other or from the negative to the positive of the power source if we add a light bulb to the closed circuit the electrons will have to pass through it in order to get to the other terminal thus producing a light electric current is the movement of electric charge in a wire over a period of time the symbol for electric current is i one coulomb of charge passing through a piece of wire over one second is equal to one ampere of current ampere is the unit of measurement of electric current alright that's all for this video in the next video we will talk about coulomb's law and electric field i hope you enjoyed this video and learned something new don't forget to subscribe and for more tutorials visit my website howtomechatronics.com