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DC ELECTRICAL CIRCUITS

DC ELECTRICAL CIRCUITS. CURRENT FLOW. DC ELECTRICAL CIRCUITS. Current is defined as the flow of electrical charge from one point to another. Coulomb’s law states that: 1) Like charges repel 2) Unlike charges attract. DC ELECTRICAL CIRCUITS.

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DC ELECTRICAL CIRCUITS

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  1. DC ELECTRICAL CIRCUITS CURRENT FLOW

  2. DC ELECTRICAL CIRCUITS • Current is defined as the flow of electrical charge from one point to another. • Coulomb’s law states that: 1) Like charges repel 2) Unlike charges attract

  3. DC ELECTRICAL CIRCUITS • An atom that has the same number of protons and electrons is electrically balanced. • An atom that loses one or more electrons is called an ion. • The process of changing an atom to an ion is called ionization. • Ionization is significant in current flow.

  4. DC ELECTRICAL CIRCUITS • An atom that receives one or more electrons is negatively charged and is called a: negative ion. • A balanced atom that loses one or more electrons is positively charged and is called a: positive ion. NEGATIVE ION 4 PROTONS 5 ELECTRONS NEUTRAL ATOM 5 PROTONS 5 ELECTRONS POSITIVE ION 5 PROTNS 4 ELECTRONS

  5. DC ELECTRICAL CIRCUITS • Conductivity of an atom depends on its valence shell. • The greater the number of electrons in the valence shell the less it conducts. • A valence shell with 7 electrons is less conductive than a valence shell of 2 electrons.

  6. DC ELECTRICAL CIRCUITS • Remember that the valence shell is the outer most orbit of an atom. HERE IS A REPRESENTATION OF A COPPER ATOM. HOW MANY ELECTRONS ARE IN THE VALENCE SHELL?

  7. DC ELECTRICAL CIRCUITS • Each orbit or shell has a letter designation and a maximum number of electrons that it can hold.

  8. DC ELECTRICAL CIRCUITS • Valence electrons are the easiest to break from their parent atom. • If they gain enough energy from an external force and break free they are known as free electrons and will randomly move from atom to atom.

  9. DC ELECTRICAL CIRCUITS • Conductors: have 3 or fewer valence electrons. • Insulators: have 5 or more valence electrons. • Semi-conductors: usually have four electrons, they aren’t good conductors or insulators.

  10. DC ELECTRICAL CIRCUITS • The Bohr model of silver, gold and copper are pictured below, notice they all have one electron in their valence shell. NUMBER OF ELECTRONS IN EACH SHELL

  11. DC ELECTRICAL CIRCUITS

  12. DC ELECTRICAL CIRCUITS • CURRENT: I = E / R • The movement or the flow of electrons. • Current is represented by the letter (I). • The unit of measure for current is the ampere or amp.

  13. DC ELECTRICAL CIRCUITS • The amount of current is the sum of the charges of the moving electrons past a given point. • Electric charge is measured in coulombs. • It takes 6.25 x 10 to the 18th power of charges to make 1 coulomb.

  14. DC ELECTRICAL CIRCUITS • When 1 coulomb of charge moves past a single point in one second it is called an amp. I = Q(coulomb) / T(time) • Charge differs from current. • Q is an accumulation of charges while I measures the intensity of moving charges.

  15. DC ELECTRICAL CIRCUITS • VOLTAGE: E = I X R • The force that causes electrons to flow is voltage. • Also referred to as potential difference and EMF, electromagnetic force.

  16. DC ELECTRICAL CIRCUITS • 1 volt pushing 1 coulomb of current produces 1 joule of work. • A joule is the amount of work that can be produced by both voltage and current. • The actual work accomplished in a circuit is a result of the potential difference between the two ends of a conductor.

  17. DC ELECTRICAL CIRCUITS • Electrons are usually in free drift mode until we apply a potential difference to the conductor.

  18. DC ELECTRICAL CIRCUITS

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