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# Basic dc circuit theory

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### Basic dc circuit theory

1. 1. Basic Electrical DC Circuit Theory Science Olympiad 2013
2. 2. It all starts with the ATOMAn ATOM iscomposed of threeparts: PROTONS NEUTRONS ELECTRONSThe tightly –bound clump ofprotons &neutrons in thecenter of theATOM is called thenucleus THE ELEMENT OF CARBON
3. 3. PROTONS = IDENTITYThe tightly – bound clump of protons & neutrons inthe center of the ATOM is called the nucleus. Thenumber of protons in the nucleus is what determinesits elemental identity; in this case CARBON. THE ELEMENT OF CARBON
4. 4. NEUTRONS = MASSIf neutrons are added or gained in the nucleus theATOM will retain the same chemical identity, but itsMASS will change slightly and it may acquire strangenuclear properties such as radioactivity
5. 5. ELECTRONS = ATTRACTIONElectrons, unlike protons and neutrons, have morefreedom to move around. In fact they can be knockedout of position and leave an ATOM entirely; if thathappens the ATOM keeps its chemical identity but avery important imbalance happens. electrons & protons are unique because they are attracted to one another over a distance. It is this attraction over distance which causes the attraction between rubbed objects, where electrons are moved away from their original atoms to reside around atoms of THE ELEMENT OF another object. CARBON
6. 6. POSITIVE & NEGATIVE CHARGES ELECTRONS (-) PROTONS (+) Have a NEGATIVE Have a POSITIVE charge charge An object whose An object whose atoms have atoms are lacking received a surplus electrons is of electrons is positively charged negatively charged THE ELEMENT OF CARBONIn equal numbers within an atom, they counteract each others presence so that the net charge within the atomis zero. This is why the picture of a carbon atom has six electrons: to balance out the electric charge of the sixprotons in the nucleus. If electrons leave or extra electrons arrive, the atoms net electric charge will beimbalanced, leaving the atom "charged" as a whole, causing it to interact with charged particles and othercharged atoms nearby. Neutrons are neither attracted to or repelled by electrons, protons, or even otherneutrons, and are consequently categorized as having no charge at all.
7. 7. What is A Circuit? Electrons flow from the zinc casing to the carbon rod, lighting the bulb in the process. The zinc casing acts as a negative electrode; the carbon rod acts as a positive electrode. The ammonium chloride paste acts as the electrolyte and the carbon and the manganese dioxide mixture around the carbon rod extends the batterys life.Lets take an example of a battery, for now. The battery has a positive (+) end, and aminus ( - ) end. When you touch a wire onto both ends of the battery at the same time,you have created a circuit. What just happened? Current flowed from one end of thebattery to the other through your wire. Therefore, our definition of circuit can simply be anever-ending looped pathway for electrons (the battery counts as a pathway!).
8. 8. Requirements for a CircuitMust have a closed conducting path which extendsfrom the positive terminal to the negative terminal. Think of this as a circle or a loopALL connections must be made by conductingmaterials capable of carrying charge.
9. 9. CurrentThis battery takes these negatively charged electrons from a chemical reaction inside the battery,pushes them out of the negative end of the battery, and into the wire. These electrons will thenbump electrons in the atoms of the wire over and over until finally electrons arrive back at thepositive end of the battery. Elements which allow this process of "bumping" those electrons onover determines how conductive the element is. So, when theres a current, its just electronsbumping each other from atom to atom and flowing on.