Electronics

Basic Electronics

Basic Electrical Principles and 

the Functions of Components

Basic Electrical Principles

• Conductors - keep loose grip on their electrons and allow electrons to move freely. Metals are usually good conductors.

• Insulators - keep close hold of their electrons and do not allow free movement of electrons. Glass, wood, plastic,mica,fiberglass and air are good insulators.

• Electromotive Force (EMF) is the force that moves electrons through conductors. Its unit of measure is the Volt. Think of it as pressure.

• Voltage Source - has two terminals (+ and -). Some examples are car batteries (12 volts DC), D cell batteries (1.5 volts DC) and a wall socket (120 volts AC).

• Current - is the flow of electrons. It is measured in amperes.

• Resistance (ohms, Ω) - is the ability to oppose an electrical current.

Circuit Definitions

A circuit must close to be complete

Ohm’s Law

• Ohm’s Law relates Current (I), Voltage (E) and Resistance(R)

• The relationship can be written three ways:

» E = I x R

» I = E / R

» R = E/I

Resistor

Calculating Resistance

• Series:R=R1+R2+R3+R4

(the voltage adds up)

• Parallel:1/R=1/R1+1/R2+1/R3

(the current adds up)

Capacitors

• Capacitors store energy in an electric field

• Basic unit of capacitance is the farad (f)

• Series: 1/C=1/C1+1/C2+1/C3

• Parallel: C=C1+C2+C3

• Capacitance is determined by 3 factors:

» plate surface area

» plate spacing

» insulating material (dielectric)

Variables Determining

Capacitance

Parallel Capacitors Increase Plate

Area; increase charge so C

Capacitors Store Energy in

Electric Field

Inductors

• Inductors store energy in a magnetic field

(like a little electromagnet)

• Basic unit of inductance is the henry (h)

• Parallel: 1/L=1/L1+1/L2+1/L3

• Series: L=L1+L2+L3

• Inductance is determined by 4 factors:

» number of turns

» permeability of the core

» cross sectional area of the core

» spacing of the turns

Variables Determining

Inductance

Power

• Power is the rate of energy consumption.

• The basic unit of power is the watt (W)

• Power can be calculated as follows:

»P = I x E

• Since E = I x R, you can also say:

»P = I2 x R

• Since I = E / R, you can also say:

»P = E2 / R

Amplifiers

• Tubes and transistors

amplify signals applied to

base or control grid.

• Transistors have

advantages:

• size

• power consumption

• cooling

• robustness

• Tubes have advantages:

• high power