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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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Electrical PrincipalsChapter 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


  • 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.


  • 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.


  • 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.


  • 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

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).

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.


  • 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.

Resistors, Resistance, and Resistivity


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

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).

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.

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.

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.

Resistors, Resistance, and Resistivity

Capacitance, Capacitors, Diodes and Transistors

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.

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.

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.

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.

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.

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.

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.

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.

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.

Capacitance, Capacitors, and Diodes


  • 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.


  • 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.


  • 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.


  • 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.


  • 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.


Digital Logic Gates

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).

Digital Logic Gates


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