electronics information

There are two major types of resistors used today

1) Fixed resistor: have a fixed resistance 2) Variable resistor: (rheostat or potentiometers), have resistances that can be changed a) Potentiometers: are useful in changing the voltage drop across a component in a circuit. In electronic applications, they can be used to help adjust the volume on a TV, radio or stereo. b) Rheostats: are useful in changing the current in a circuit and can be used as light dimmers or to control the speed of small motorized devices

Two subatomic particles are found within the nucleus:

1) Protons: have a positive charge 2) Neutrons: are neutrally charged

Three materials that are most often used as conductors are

1) Silver: best conductor as it exhibits the lowest resistance. Unfortunately, silver is relatively expensive 2) Copper: has only a slightly higher resistance than silver, but is much less expensive 3) Aluminum: higher resistance than copper, and exhibits some other characteristics that make it even less than desirable for use in electrical application

In North America Ac is always delivered at

60 cycles per second (hertz)

Capacitor can store an electrical charge because the

DC source creates an excess of electrons on the negative plate and a shortage of electrons on the positive plate. The electrostatic attraction between the positive and negative charges keeps the charge intact in the capacitor, even when the voltage source is removed. The capacitor will discharge itself if a conductor is connected across it, as a path is when created for electrons to flow from the negative plate to the positive plate. A capacitor will allow AC to flow across it, but will block dc. This is why DC is most useful for "charging up" a capacitor

The relationship between voltage, current, and resistance through a wire is summed up in

Ohm's law

Resistors

a component that can be used to limit current and/or a voltage. A resistor does what its name suggests: it creates a specific amount of resistance that generates a voltage drop when current passes through it

Transistor

a component that has revolutionized the construction of electronic devices such as computers, calculators and radios. A transistor is versatile, as it can be used as an electrical switch, an amplifier, or a current regulator

Electrical power

a term that refers to the actual rate at which energy is provided to and consumed by an electric circuit

If two or more loads are added to a series circuit, there resistances

add together, creating what's called the total or effective resistance across the circuit i. Rtot=R1+R2+R3+...

doping

adding impurities to pure forms

Capacitors

aka condensers are electrical storage units. They are constructed using two metal conducting plates with a very thin insulator (known as a dielectric) between them. Air can also serve as a dielectric

Any time voltage increases, current will

also increase. So in materials with high resistance (that is, in poorer conductors), a higher voltage must be used to get the same current

Current is measured in

amperes, or amps for short, and an ampere is defined as one coulomb {c}, the basic unit of electrical charge, flowing past a given point in one second (if five coulombs of charge were to pass by a point every second, this would be a current of five amps (5 A)

Conductor

an element that allows electrons to flow freely. What all conductors have in common is one or more mobile valence electrons per atom that are free to move from one atom to another, as each valence shell has more empty spots than electrons

Parallel circuits

are the exact opposite of a series circuits in that voltage is the same throughout each parallel branch of the circuit, while current flow varies. Since voltage is a measure of the difference in electric potential between two points, the voltage across alternate paths connecting the same two pints in a circuit must also be equal i. V1=V2=V3=...

Fuses

are thin wires that melt when current exceeds a prescribed amount, thereby preventing any further electricity flow. This prevents any potential damage to the electric device. One disadvantage of using a fuse is that when it has melted, or "blown," it has to be replaced before the circuit will work again. Fuses with different current rating can be used depending on the device specifications

The nucleus is the heaviest part of the

atom and accounts for the majority of atom's mass

Matter is composed of

atoms, which are the smallest particles that elements can be broken into and still retain the properties of that element. An atom is itself broken into even smaller components, called subatomic particles

Load

basically a source of resistance that converts electrical energy into some other energy form

The smaller the resistance a material has, the

better a conductor it is.

Voltage, which refers specifically to a difference in electric potential at two different points

can also be calculated across a single load. This is also known as the voltage drop across a load, and the total of all voltage drops across each load in a series circuit is equal to the total voltage of the complete circuit, which is equal to the voltage source itself i. Vtot=V1+V2+V3+...

A capacitor's opposition to the flow of current is known as

capacitive reactance, and this is measured in ohms. Capacitive reactance is inversely proportional to the frequency of the AC signal. In other words, the higher the frequency, the less opposition there is to the flow of AC across the capacitor

Electrical current, similarly, is measured by the amount of

charge flowing past per unit of time

In order for electric current to flow, there must be a

circuit for it to follow

The voltage source is the beginning and end of the

circuit. The negative side repels electrons, forcing them to move through the circuit. The positive side helps by attracting electrons, and an electron emitted from the negative side will eventually traverse the complete circuit before arriving at the positive side

There must be electrical "pressure" applied to a

conductor to cause electrons to move. For an electron, the "pressure" is caused by electromagnetic repulsion from a large negative charge, like that found at the negative terminal of a battery

Alternation current (AC)

current that changes direction (moves back and forth) many times in a second as it moves in a conductor. Household electrical outlets deliver alternating current. AC provides a more efficient way to transport electricity from the power stations to your home or business

Direct current (DC)

current that flows in only one direction in a conductor. This is the type of current that is delivered by a battery. Many electronic devices, like cell phones and laptops, work on DC

The transistor works by using a small amount of

current to control a large amount of current. In the case of an NPN transistor, a positive voltage applied to the base will "turn on" the transistor and allow a relatively large current to flow from the collector to the emitter. The moment the positive voltage is removed from the base, the transistor turn off the stops the current flow

Adding a load in parallel, even if that load's resistance is high,

decreases the total or effective resistance of a circuit, because even though it has resistance, it provides an additional path while doing nothing to constrain the existing one. The formula for adding resistances in parallel is slightly more compacted one, but it's very useful 1/Rtot = 1/R1 + 1/R2 +1/R3+...

As resistance in a conductor increases, current flow

decreases. This means that current and resistance are inversely proportional

Conventional current

defined by the (imaginary) flow of positive charge and is opposite in direction to actual electron flow

Four diodes can be connected in a

diamond configuration to create a full-wave rectifier, which is the foundation for most DC power supplies.

p-type and N-type materials can do little by themselves; however, when the two are joined, a

diode is formed. A diode is an electrical one-way valve that results from interactions at the junction of P-type and N-type material. Current can pass easily in one direction, but is blocked in the opposite direction

voltage is really the difference in

electric pressure between two points, such that electrons will tend to be pushed from areas of greater electric potential to areas of lesser electric potential for this reason voltage is also known as electrical potential difference. It's also referred sometimes as electromotive force

The higher the voltage that is applied to a conductor, the greater the

electrical pressure the electrons will experience, and the higher the current will tend to be. Voltage and current are therefore directly proportional

Ohm's law states that voltage (potential difference) in volts is

equal to the current in amperes multiplied by the resistance in ohms. Is represented by the formula V=IR, V=voltage aka potential difference, while I=current, and R=resistance

Electricity actually follows

every possible path, through a larger proportion of electrons will take a path of low resistance while a smaller proportion will take a path with higher resistance. For a parallel circuit, therefore, the total current through the circuit is equal to the sum of currents through each closed path Ltot=l1+l2+l3

Power

expressed in watts and can be calculated by multiplying the voltage applied to the circuit by the current that flows in the circuit P = IV

Frequency equation

f = 1/T, f = frequency in Hz and T = the amount of time for one cycle in seconds. You can used that equation to solve for either frequency or period when given one of them. Thus, with a frequency of 60 Hz, it can be determined that one complete cycle occurs in 1/60 of a second, since: T = 1/F

Since current can only flow in one direction, the orientation of the battery in a circuit is important. If current is able to flow, this is called

forward-biased. In order for the circuit to be forward-biased, the P-type material (also known as the anode) should be conducted to the battery's positive terminal and the N-type material (aka cathode) should be connected to the battery's negative terminal

In residential wiring,

ground is a common connection throughout the wiring system that protects against electrical shock. All of the wiring grounds are connected to an earth ground (such as copper rod driven into the ground or buried conduit) and this is used to guide electrical current away from panels and equipment, should an internal short circuit take place

Insulator

has a valence shell that is more than half full, or is completely full. It does not conduct electricity much at all, because its electrons are all tightly bound and will not leave their packed valence shells

Series-parallel circuit

has some components, such as an on/off switch, wired in series with a number of loads that are connected in parallel

If a load's resistance were to decrease, the current flowing in the circuit would

increase. However, if the circuit were broken, as in a wire (conductor) being disconnected, no current would flow. This would be called and open circuit

The outer shell of an atom is known as

its valence shell, and the number of electrons that reside in the valence shell are what determines whether an elements a conductor, a semiconductor, or an insulator

A circuit is a complete

loop or path that electricity can follow. There are three essential components of an electrical circuit: a 1)voltage source, a 2)load and 3)conductors to connect the load to the voltage source. When these three components are connected so that current can flow, we have a closed (completed) circuit

NPN transistor

made up of a thing piece of P-type material sandwiched between two pieces on N-type material

voltmeter

measures voltage

PNP transistors work opposite to NPN transistors. A PNP transistor requires a

negative voltage at the base to turn it on , and the current then flows from the emitter to the collector

a Semiconductor with a valence shell that is exactly half full, is

neither a good conductor nor a good insulator, but it has some remarkable properties that make it very useful for making electronic components

N-type material

new material is still electrically neutral, but is able to conduct electricity due to presence of free electrons

Electrons occupy various energy levels around the

nucleus, known as shells, and each time one becomes full, a new one is begun

Short circuit

occurs when a load is bypassed with a conductor for some reason. Since current and resistance are inversely proportional, the flow of current will increase. This could be caused by something as simple as the insulation on the wires leading to and from the load becoming frayed and allowing the wires to come into direct contact with each other. If a short circuit occurs in part of the series circuit, the net effect is merely to remove the load that was bypassed as a result of the short circuit. If, however, the short circuit occurs at any load in parallel circuits or bypasses all the loads in series circuits, the resistance of the circuit as a whole is reduced to near zero and a dangerous surge in current could occur. For this reason, it is a good safety precaution to protect circuits with fuses or circuit breakers

Resistance is measured in

ohms, and one ohm is defined as the amount of resistance that will allow one ampere of current to flow if one volt of electrical pressure is placed on a conductor. The symbol for the ohm is the Greek letter omega, and resistance can be measured using an ohmmeter

Since a diode only allows current to flow in one direction, it will

only pass either the upper or lower half of the AC waves. This is known as half-wave rectification

resistance

opposition to the flow of current

Capacitance

or the ability of the capacitor to store charge, is represented by the symbol C, and its unit of measurement is the farad. A farad is sufficient capacitance to store one coulomb of electrons with an electrical potential of one volt applied

Semiconductor

refers to an element that has four electrons in its valence shell. Since the bonds between these four electrons and the nucleus are somewhat strong, these elements are neither good conductors nor good insulators. Elements that are widely recognized as semiconductors are silicon and germanium

Ground

represents a place of lowest potential in a circuit. Since the potential difference is largest between any point in the circuit and the ground point, any "stray" electricity will follow this path since resistance is low here. This is important to prevent shock due to external influences such as lightning, or due to internal circuit failure where conducting wires are compromised

With a parallel circuit arrangement, each load is wired in a

separate path. If any one of these paths were to have a break or gap, current flow would still continue through the other paths, so there would still remain a closed circuit

An electrical circuit that has only one path for current to flow is known as a

series circuit

Circuit breakers

serve the same function as fuses, but have the advantage of being able to be reused multiple times. However, they respond more slowly to increases in current than fuses do, and are more expensive to install. There are several types of circuit breakers, but the underlying principle behind their function remains the same. One class of circuit breakers consists of bimetallic strip that bends away fro its contract in a circuit when too much current is flowing. This makes a break in the circuit and prevents further current flow. Another class of circuit breakers use an electromagnet to cause a branch in the circuit. When the current rises to a certain value, the ferrous material is sufficiently magnetized to cause the circuit to open, thereby inhibiting further current flow

Since there are no moving parts in a transistor and it is made from solid silicon, it is known as a

solid-state device, which makes it very reliable. Very compact in design, as thousands of transistors can fit into a single integrated circuit. An integrated circuit is one that contains all necessary circuit components in one single silicon chip. Transistors are the bedrock of logic operations that a computer uses to process information

Rectification

the conversion of AC into DC

inside the transistor, wires connect to the three pieces of semi-conductor material. Each piece is given a name

the middle piece is always called the base; the two outside pieces are called the collector and the emitter. The symbol for the transistor has an arrow that identifies the emitter. The direction of the arrow tells us what type of transistor it is. The key to remembering which symbol identifies which type of transistor is that the arrow always points in the direction of the N-type material

Current

the rate of flow of electrons through a conductor

Since there is only one path for current to follow in a series circuit, the current flow will be

the same in all parts of the circuit. It wouldn't make sense if a plane taking off from NY and then landing in Miami with twice as many passengers i. l1=l2=l3=...

Electrons

the third type of subatomic particle, are in motion around the nucleus and have a negative charge

PNP transistor

two pieces of P-type material that have a piece of N-type material between them

Fixed resistors

used a color band system to enable us to determine their resistance in ohms. The first color gives the first number. The second color gives the second number, and the third number gives the multiplier or the number of 0's behind the numbers

Electrical pressure is known as

voltage, and it is measured in volts (v)

P-type material

when a doped semiconductor contains mostly free holes

Reverse-biased

when voltage is applied across a diode in such a way that the diode prohibits current