Summary and Introduction to Advanced Circuits

 

Summary of Some Important Concepts to Date (Chapters 1-15)

 

The study of electronics is focused on

 

    n  Resistance (Chapter 3)

   

    n  Resistance in Series and in Parallel (Chapters 6 and 7)

 

    n  Inductance (Chapter 14)

 

    n  Capacitance (Chapter 15)

 

    n  A Combination of These in Series and Parallel Circuits (Chapter 16)

 

The remaining chapters build on these concepts

 

    n  Semiconductors (Chapter 17)

 

    n  Transistors and Amplifiers (Chapter 18)

 

    n  Integrated Circuits (Chapter 19)

 

    Digital Circuits (Chapter 20)

 

   

Resistance

 

Resistor

 

    n  Component used to create desirable voltage drops and limit current values in electric circuits.

 

    

 

Resistance (R)

 

    n  A characteristic of a material that opposes the flow of electrons.

 

    n  Measured in ohms, W

 

Resistance of Resistors in Series:   R_T = R₁ + R₂ + ... + R_N

 

 

Resistance of Resistors in Parallel:  1/R_T = 1/R₁ + 1/R₂ + ... + 1/R_N

 

 

Inductance and RL Circuits

 

Inductance (L)

 

    n  Inherent property of an electric circuit that opposes a change in current.

 

    n  Occurs only when there is a change in voltage - otherwise only resistance in the coil is involved

 

    n  Property of a circuit whereby energy may be stored in a magnetic field.

 

   n  Unit of Inductance: Henry (H)

 

Inductor

 

    n  An electrical component (such as a coil) that is used to produce inductance in a circuit.

 

 

 

Air Core Inductor Symbol	Air Core Inductor	Iron Core Inductor

 

Inductance of Coils in Series: L_T = L₁ + L₂ + .... + L_N

 

Inductance of Coils in Parallel: 1/L_T = 1/L₁ + 1/L₂ + ... + 1/L_N

 

Lenz's Law: The field created by induced current is of such a polarity that it opposes the field of the permanent magnet.

 

RL Circuit: Circuit that contains resistance and inductance

 

 

 

 

Time Constant, τ, in an RL Circuit

 

    n  τ = L/R

 

    n  L in henrys, R in ohms

 

   n  This is the time, in seconds, for the current to reach 63.2 percent of its maximum value or to decrease to 36.7 percent of its value

 

 

 

NOTE: You cannot instantaneously change the current across an inductor

Capacitance and RC Circuits

 

Capacitor

 

    n  A device that temporarily stores an electric charge.

 

 

 

    n  C = Q/E where

   

        C = capacitance in Farads

      Q is the charge in coulombs

      E is the voltage in volts

 

 

Capacitance

 

    n  An inherent property of an electric circuit that opposes a change in voltage.

 

Factors affecting capacitance

 

    n  Dielectric material

    n  Area of plates

    n  Distance between plates

 

RC Circuit: A circuit that contains resistance and capacitance

 

 

Time Constant, τ, in an RC Circuit

 

    n  τ = RC

 

    n  R is resistance in ohms, C is capacitance in farads

 

 

   n  Time period, in seconds, required for the voltage of a capacitor in an RC circuit to increase to 63.2 percent of maximum value or decrease to 36.7 percent

       of maximum value 

 

 

 

 

 

NOTE: You cannot instantaneously change the voltage across a capacitor

 

Reactance

 

Reactance (X)

 

    n  Opposition to alternating current as a result of inductance or capacitance.

 

Inductive Reactance (X_L)

 

    n  Reactance caused by a conductor

    n  Opposition to AC as a result of inductance.

 

Capacitive Reactance (X_C)

 

    n  Reactance caused by a capacitor.

    n  Opposition to AC as a result of capacitance.

 

 

Impedance

 

 

Impedance (Z)

 

    n  Total resistance to the flow of an alternating current as a result of resistance and reactance.         Z = X_L + X_C

    n  Impedance is measured in ohms

 

 

Ohm's Law for AC Circuits

 

    n  Same as earlier, except Z is used in place of R