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Electrical Principals Chapter 4

Electrical Principals Chapter 4. Conductors, Conductance, Insulators, Resistivity, Temperature on Conductors, Resistors, Resistor Types, Resistor Values, Variable Resistors, Capacitors, Diodes, Transistors, Digital Logic Gates, . Conductors, Temperature Effects on Conductors, and Insulators.

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Electrical Principals Chapter 4

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  1. Electrical PrincipalsChapter 4 Conductors, Conductance, Insulators, Resistivity, Temperature on Conductors, Resistors, Resistor Types, Resistor Values, Variable Resistors, Capacitors, Diodes, Transistors, Digital Logic Gates,

  2. Conductors,Temperature Effects on Conductors, and Insulators

  3. Conductors • A Conductor is a material that has very little resistance and permits electrons to move through it easily. • Conductors include wire, cable, and cord. • Electrical circuits and components are connected using Conductors.

  4. Conductors • Conductor material include copper, aluminum, copper-clad aluminum, steel, and bronze. • Copper and Aluminum are the most commonly used materials. • Copper is most common. • Copper is preferred because it has a lower resistance than aluminum for any given wire size.

  5. Conductors • Conductance is the measure of how good a conductor is at carrying current. • Conductance is inversely proportional to resistance. • A good Conductor has a high Conductance value and a very small resistance to current flow.

  6. Conductors • Conductors are not meant to offer any resistance or opposition to current flow. • Conductance is the measure of how good a Conductor is, and even the best Conductors have some value of resistance. • We can calculate a Conductor’s resistance with the formula R=V/I

  7. Temperature Effects on Conductors • When heat is applied to a Conductor, the atoms within the Conductor convert this thermal energy into mechanical energy or movement. • These random moving atoms cause collisions between the directed electrons (current flow) and the adjacent atoms, resulting in an opposition to current flow (resistance).

  8. Temperature Effects on Conductors • This means the greater the heat applied to the conductor (more current flowing), the greater the atom movement, causing more collisions of atoms to occur and consequently, greater conductor resistance. • More current more heat. More heat more resistance.

  9. Insulators • Insulators is any material that offers high resistance or opposition to current flow. • Remember Conductors permit the easy flow of current. • Insulators can, with sufficient pressure or voltage applied across them, “break down” and conduct current.

  10. Resistors, Resistance, and Resistivity

  11. Resistivity • Resistivity is the resistance (in Ohms) that a certain length of conductive material (in feet) will offer to the flow of current.

  12. Resistors, Resistance, and Resistivity • Electrical Resistance is opposition to the flow of electrons through any material. • A Resistor is a device that limits the current flowing in an electronic circuit. • Resistors are classified by their resistance value (in Ώ) and their power dissipation (in Watts).

  13. Resistors, Resistance, and Resistivity • Resistors are used for dividing voltage, reducing voltage, developing heat, and limiting current. • Resistors may be fixed, variable or tapped. • A Fixed Resistor is a Resistor with a set value, such as 100Ώ.

  14. Resistors, Resistance, and Resistivity • A Variable (adjustable) Resistor is a resistor with a set range of values, such as 0Ώ to 1000Ώ. • A Tapped Resistor is a resistor that contains fixed tap points of different resistances. • A Thermistor is a device that changes resistance with a change in temperature. Thermistors are semiconductor devices.

  15. Resistors, Resistance, and Resistivity • There are two types of Thermistors – positive temperature coefficient (PTC) and the negative temperature coefficient (NTC). • A PTC Thermistor has an increasing resistance value with an increase in temperature. • A NTC Thermistor has a decreasing resistance value with an increasing in temperature. The NTC Thermistor is the most common type.

  16. Resistors, Resistance, and Resistivity

  17. Capacitance, Capacitors, Diodes and Transistors

  18. Capacitance, Capacitors, and Diodes • Capacitance is the ability to store energy in the form of an electrical charge. • Capacitance is the property of an electric device that permits the storage of electrically separated charges when potential differences exist between the conductors.

  19. Capacitance, Capacitors, and Diodes • A Capacitor is an electric device designed to store electrical energy by means of an electrostatic field. • Capacitors are used as filters in AC circuits to block DC voltages in electronic circuits, and to improve torque in motors.

  20. Capacitance, Capacitors, and Diodes • Capacitors include fixed, variable, and electrolytic polarized. • Once Capacitors are discharged, the must be recharged. • Tolerance of some Capacitors is indicated by a letter code following the number.

  21. Capacitance, Capacitors, and Diodes • A Diode is a semiconductor device that offers very high opposition to current flow in one direction and very low opposition to current flow in in the opposite direction. • Diodes are also know as Rectifiers because they change AC into pulsating DC.

  22. Capacitance, Capacitors, and Diodes • Diodes are rated according to their type, voltage, and current capacity. • The most common types of diodes include zener, tunnel, photoconductive, and light-emitting diodes (LED). • Diodes are a available in current ranges of a few milliamps to over 1000A.

  23. Capacitance, Capacitors, and Diodes • A Zener Diode is a silicon PN junction that differs from a standard diode in that it operates in the reverse breakdown region. • A Zener Diode operates as a voltage regulator in an electronic circuit. • Zener Diodes allow varying amounts of reverse current flow through them and continue to maintain a relatively constant voltage drop when reverse biased.

  24. Capacitance, Capacitors, and Diodes • A Tunnel Diode is a diode designed so that the current flowing through the diode decreases with an increase in applied voltage for a specific range of forward voltage. • Tunnel Diodes operate as an amplifier or oscillator in an electronic circuit. • Tunnel Diodes exhibit negative resistance when operated within a specific range of forward voltage. • Tunnel Diodes are used in logic circuits and for level sensing.

  25. Capacitance, Capacitors, and Diodes • A Photoconductive Diode is a diode that conducts current when energized by light. • Photoconductive Diodes decrease resistance as light increases. • The Diode is made of photosensitive material that decreases in resistance with an increase in light.

  26. Capacitance, Capacitors, and Diodes • A Light Emitting Diode (LED) is a Diode that emits light when forward current is applied. • In an LED is produced when current is passed through the diode. • LEDs are commonly used as visual indicators because they have a very long life.

  27. Capacitance, Capacitors, and Diodes

  28. Transistors • A Transistor is a three-terminal device that controls current through the device depending on the amount of voltage applied to the base. • Transistors are made of semiconductor material. • Transistors are used to start and stop (switch) current flow or to increase (amplify) current flow in DC circuits.

  29. Transistors • Transistors can be NPN or PNP, Unijunction, and Junction Field-Effect Transistors (JFET), and Phototransistors. • An NPN Transistor is a transistor that is formed by sandwiching a thin layer of P-type material between two layers of N-type material.

  30. Transistors • An PNP Transistor is a transistor that is formed by sandwiching a thin layer of N-type material between two layers of P-type material. • NPN and PNP transistors function as a switch. They start, stop, or increase the flow of current in a DC circuit. • Transistors also function as amplifiers in allowing a very small current to control a much larger current.

  31. Transistors • A Unijunction Transistor (UJT) is a transistor consisting of N-type material with a region of P-type material doped within the N-type material. • A UJT is used in timer circuits. • A Junction Field-Effect Transistor (JFET) is a device in which output current is controlled by the voltage on the input.

  32. Transistors • A Phototransistor is a transistor that controls the amount of current flowing through the emitter/base junction based on the amount of light. • Phototransistors include NPN and PNP transistors. • There is an increase of current flow with an increase in light. A Phototransistor is a combination of a Photodiode and a Transistor.

  33. Transistors

  34. Digital Logic Gates

  35. Digital Logic Gates • A Digital Logic Gate is a circuit that performs a special logic operation such as AND, OR, NOT, NOR, NAND, and exclusive OR. • Digital Logic Gates are used in most electronic devices. • Digital circuits operation on binary signals. Binary signals have two states – the signal is high (1) or low (0) … on (1) or off (0).

  36. Digital Logic Gates

  37. QUESTIONS!?!?!?!?!?!?!?

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