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Electricity

Electricity. Circuits and Circuit Elements. Circuits. Electric circuit – a set of electrical components connected so that they provide one or more complete paths for the movement of charges Charges move from the battery through a path back to the battery. Circuits.

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Electricity

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  1. Electricity Circuits and Circuit Elements

  2. Circuits • Electric circuit – a set of electrical components connected so that they provide one or more complete paths for the movement of charges • Charges move from the battery through a path back to the battery

  3. Circuits • Switches are used to open and close the circuit • If the circuit is open, there is no complete path for the charge to travel • Charge cannot flow, so there is no current • If the circuit is closed, there is at least one complete path for the charge to travel

  4. Circuits • Schematic diagram – a graphic representation of an electric circuit or apparatus, with standardized symbols for the circuit components

  5. Circuits

  6. Series and Parallel Circuits • Series – describes a circuit or portion of a circuit that provides a single conducting path • One path for current to travel • If one element is removed, the circuit will not work • If one element doesn’t work, the circuit will not work

  7. Series and Parallel Circuits • Parallel – describes components in a circuit that are connected across common points, providing two or more separate conducting paths • More than one pathway • Charge moves through the path of least resistance • If one part is removed or doesn’t work the circuit may continue to work

  8. Fuses and Circuit Breakers • Overloaded – condition when electrical wires carry more than a safe level of current • Short circuit – accidental creation of an alternative pathway • Reduces the resistance in the circuit • Increases the current

  9. Fuses and Circuit Breakers • Short circuits • Leads to overload • Grounding is used to prevent electric shock from short circuits • Fuse – an electrical device containing a metal strip that melts when current in the circuit becomes to great • Used to prevent overload

  10. Fuses and Circuit Breakers • Circuit breaker – a device that protects a circuit from current overloads • Trip when the current overloads • Acts like a switch

  11. Resistors in Series • Series – describes a circuit or portion of a circuit that provides a single conducting path without junctions • When resistors are arranged in series, the current flowing through each resistor is the same • Equivalent resistance – the total resistance of a circuit

  12. Resistors in Series

  13. Resistors in Series • For resistors in series, the equivalent resistance is equal to the sum of all of the resistors • Req = R1 + R2 + R3… • Total Potential difference (voltage) = Current * Equivalent Resistance • VTot = IReq • The equivalent resistance of a series combination of resistors is always greater than any individual resistance

  14. Resistors in Series • Potential difference across a given resistor can be calculated by multpying the current (which is constant) by the resistance of the given resistor • V1 = IR1 or V2 = IR2 • In a series circuit, all of the elements must be able to conduct electrical charge • If one bulb goes out or one wire gets disconnected, the entire circuit fails

  15. Resistors in Parallel • Parallel – describes two or more components in a circuit that are connected across common points or junctions, providing separate conducting pats for the current • There is more than one pathway through the circuit or part of a circuit • Resistors in parallel have the same potential difference across them • V is constant • The sum of the individual currents in parallel resistors equals the total current • ITot = I1 + I2 + I3 …

  16. Resistors in Parallel

  17. Resistors in Parallel • The equivalent resistance of resistors in parallel can be calculated using a reciprocal relationship • 1/Req = 1/R1 + 1/R2 + 1/R3 … • The equivalent resistance is always less than the smallest resistance in the group of resistors • Parallel circuits do not require all elements to conduct • The circuit will continue so long as there is at least one complete pathway from one terminal to the other

  18. Resistors in Parallel

  19. Resistors Combined Both in Parallel and in Series • Complex circuits have resistors arranged both in series and in parallel • You must simplify the groups of resistors • Work with a small group that is all in series or in parallel • After you have simplified the small groups, start combining groups until you have “created” a de facto simple circuit and can find the equivalent resistance for the circuit • Work backward to find current or potential difference

  20. Resistors Combined Both in Parallel and in Series

  21. Resistors Combined Both in Parallel and in Series

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