8085 MP pin diagram

FEEDBACK

Feed back

Basic Electrical Terms

Basic Electrical Terms

AC and DC: Abbreviations for alternating current and direct current respectively. 

Current - A movement of electricity analogous to the flow of a stream of water. 

Direct Current - An electric current flowing in one direction only (i.e. current produced 

using a battery). 

Alternating Current - a periodic electric current that reverses its direction at regular 

intervals. 

Accessible: Three common uses of accessible: (Wiring methods) - Capable of being removed 

or exposed without damaging the building structure of finish, or not permanently enclosed by 

such. Wires in concealed raceways are not considered accessible. (Equipment) -Admitting close 

approach; not guarded by locked doors or other effective means. 

Readily Accessible - Capable of being reached quickly for operation, renewal, or 

inspections without the requirement of climbing over or removing obstacles or use of 

portable ladders, chairs, etc. 

Amp or Ampere: The unit of intensity of electrical current (the measure of electrical flow), is 

abbreviated a or A. 

Box: An enclosure designed to provide access to the electrical wiring system. Uses include but 

are not limited to provide device and lighting outlets and wiring system junction points. Specially 

designed boxes are required for the support of listed ceiling fans weighing less than 35 lb (15. 

kg). Fans exceeding this weight limit must be supported independently of the outlet box. 

Circuit Breaker: A device designed to open and close a circuit by non-automatic means and to 

open the circuit automatically on a predetermined over current without damaging itself when 

operated according to its rating. 

Circuit: A complete path from the energy source through conducting bodies and back to the 

energy source. 

Conductor: a substance or body capable of transmitting electricity. Bare - A conductor having 

no covering or electrical insulation whatsoever. 

Covered - A conductor encased within material of composition or thickness that is not 

recognized by the NEC as electrical insulation. 

Insulated - A conductor encased within material of composition or thickness that is 

recognized by the NEC as electrical insulation. 

Device: A unit of an electrical system that is intended to carry but not utilize electricity. 

Equipment: A general term including material, fittings, devices, alliances, fixtures, apparatus, 

and similar items used as a part of, or in connection with, an electrical installation. 

Fuse: An over current protective device with a circuit opening part that is heated and broken by 

the passage of an over current through it.

GFCI (Ground Fault Circuit Interrupter): A device intended for the protection of personnel that 

de-energizes a circuit or portion of a circuit when the current to ground exceeds a preset value. 

"Ground Fault" is the name applied to this undesired circuit condition. In dwelling units (e.g. 

houses, apartments), GFCI protection is currently required in bathrooms, garages, outdoors, 

unfinished basements, kitchens and wet bar sinks. Other specific installations and/or areas may 

also necessitate the need for protection 

Ground: A conducting connection, intentional or accidental, between an electrical circuit or 

equipment and the earth, or some conducting body that serves in place of the earth. Other 

associated terms are: Grounded conductor - A system or circuit conductor that is intentionally 

connected to ground. This conductor has also been referred to as the neutral or common 

conductor. Grounding conductor - a conductor used to connect equipment or the grounded 

circuit of a wiring system to the grounding electrode (s). Ungrounded conductor - A current 

carrying conductor not connected to ground. 

Kilowatt-hour: Work done at the steady rate equivalent to 1000 watts in one hour. Power utility 

companies’ base their billing upon the number of kilowatt-hours (KWH) consumed. 

Labeled: Equipment or materials that a label or other identifying mark of a listing organization 

has been attached. 

Lamp: A general term for various devices for artificially producing light. 

Listed: Equipment and/or materials included in a list published by an organization concerned 

with product evaluation and production of listed items. The listing states whether the item meets 

designated standards or is suitable for use in a specified manner. Listing organizations 

acceptable to jurisdiction authorities include Underwriters' Laboratories (UL) and CSA. 

NEC (National Electrical Code): a document produced by the National Fire Protection 

Association for the purpose of the practical safeguarding of persons and property from hazards 

arising from the use of electricity. Authorities having legal jurisdiction over electrical installations 

adopt the code for mandatory application ( i.e. incorporate the code into law). 

Ohm: The unit of electrical resistance and impedance, abbreviated with the symbol omega, W. 

Resistance is the opposition offered by a substance to the passage of electrical current. 

Impedance is the apparent resistance in a circuit to the flow of alternating current. 

Ohm's Law: A statement of the relationship, discovered by the German scientist G. S. Ohm, 

between the voltage, amperage and resistance of a circuit. It states the voltage of a circuit in 

volts is equal to the product of the amperage in amperes and the resistance in ohms. E=IR

Over current: Any current in excess of the rated current or ampacity. It may result from 

overload, short circuit or ground fault. 

Overload: Operation in excess of normal full-load rating or rated ampacity which could cause 

damage or dangerous overheating if continued for a sufficient time. A fault, such as a short circuit 

or ground fault, is not an overload. See "Over Current".

potential and kinetic energy

STAR TO DELTA ___ DELTA TO STAR

FACTORS AFFECTING THE RESISTIVITY OF ELECTRICAL MATERIALS

FACTORS AFFECTING THE RESISTIVITY OF ELECTRICAL MATERIALS 


1.  Temperature  :  The  electrical  resistance  of  most  metals  increases  with  increase  of
temperature  while  those  of  semiconductors  and  electrolytes  decreases  with  increase  of
temperature.  Many  metals  have  vanishing  resistivity  at  absolute  zero  of  temperature
which is known as superconductivity.


2.  Alloying : A solid solution has a less regular structure than a pure metal. Consequently,
the electrical conductivity of a solid solution alloy drops off rapidly with increased alloy
content.  The  addition  of  small  amount  of  impurities  leads  to  considerable  increase  in
resistivity.


3.  Cold Work : Mechanical distortion of the crystal structure decrease the conductivity of a
metal because the localized strains interfere with electron movement.
4.  Age Hardening : It increases the resistivity of an alloy. 

CONDUCTIVITY OF METALS

CONDUCTIVITY OF METALS 

INTRODUCTION: 

The  most  important  properties  of  metals  are  their  high  thermal  and  electrical  conductivities. 

Silver has the highest electrical conductivity. Copper comes next and is similar to silver from the 

point  of  view  of  atomic  structure  ;  both  belonging  to  the  same  group  of  periodic  table.  The 

conductivity of copper is less than that of silver. Since supplies of copper are not abundant  in 

nature, aluminium which is light and has a high conductivity is rapidly becoming more important 

as a conductor material. Gold which has a conductivity higher than that of aluminium but lower 

than  that  of  silver  or  copper  does  not  find  use  in  electrical  industry  because  it  is  expensive. 

Metals having complex structures such as As, Sb, Bi, Sn, Hg have lower conductivities which lie 

between  those  of  ideal  metal  (very  high  conductivity)  and  of  insulators  (negligible 

conductivities). 

ENERGY

Energy is the basic necessity for the economic development of a country. Many functions necessary to present-day living grind to halt when the supply of energy stops. It is practically impossible to estimate the actual magnitude of the part that energy has played in the building up of present-day civilisation. The availability of huge amount of energy in the modern times has resulted in a shorter working day, higher agricultural and industrial production, a healthier and more balanced diet and better transportation facilities. As a matter of fact, there is a close relationship between the energy used per person and his standard of living. The greater the per capita consumption of energy in a country, the higher is the standard of living of its people. Energy exists in different forms in nature but the most important form is the electrical energy. The modern society is so much dependent upon the use of electrical energy that it has become a part and parcel of our life. In this chapter, we shall focus our attention on the general aspects of electrical energy.

Energy may be needed as heat, as light, as motive power etc. The present-day advancement in science
and technology has made it possible to convert electrical energy into any desired form. This has
given electrical energy a place of pride in the modern world. The survival of industrial undertakings and our social structures depends primarily upon low cost and uninterrupted supply of electrical energy. In fact, the advancement of a country is measured in terms of per capita consumption of electrical energy.
Electrical energy is superior to all other forms of energy due to the following reasons :

(i) Convenient form.Electrical energy is a very convenient form of energy. It can be easily
converted into other forms of energy. For example, if we want to convert electrical energy into heat,
the only thing to be done is to pass electrical current through a wire of high resistance e.g., a heater.
Similarly, electrical energy can be converted into light (e.g. electric bulb), mechanical energy (e.g.
electric motors) etc.

(ii) Easy control.The electrically operated machines have simple and convenient starting, control
and operation. For instance, an electric motor can be started or stopped by turning on or off a switch.
Similarly, with simple arrangements, the speed of electric motors can be easily varied over the desired
range.

(iii) Greater flexibility.One important reason for preferring electrical energy is the flexibility
that it offers. It can be easily transported from one place to another with the help of conductors.

(iv) Cheapness.Electrical energy is much cheaper than other forms of energy. Thus it is overall
economical to use this form of energy for domestic, commercial and industrial purposes.

(v) Cleanliness.Electrical energy is not associated with smoke, fumes or poisonous gases.
Therefore, its use ensures cleanliness and healthy conditions.

(vi) High transmission efficiency.The consumers of electrical energy are generally situated
quite away from the centres of its production. The electrical energy can be transmitted conveniently
and efficiently from the centres of generation to the consumers with the help of overhead conductors

known as transmission lines

Primary Sources of Electrical Energy

We can produce electrical energy by converting different energies available in nature. So we should look into various natural sources of energy which we use to produce electricity. Some common sources of energy are

1. The Sun
2. The Wind
3. The Water Head
4. The Fuel

The Nuclear Energy

Out of five above listed sources of energy we do not use first two in very large scale. This is because there are some limitations. But in present days water head, fuel and nuclear energy are three most primarily used natural energy sources for producing electricity. We call these three sources collectively as conventional sources of energy.

Energy of Sun

The Sun is the basic source of energy. The sun is the source of both heat and light. We can use both heat and light for producing electricity

Energy of Sun Heat

We focus sun rays at a small area with the help of concave mirror. The heat of the concentrated sun rays to heat up the water in boiler. The steam produced in boiler rotates a turbine. The turbine rotates an alternator to generate electricity. Although production cost of electricity is quite low here because no fuel like coal or diesel is required. However, production of electricity is not very popular. Because the area required for establishing this power plant is quite large even for smaller elecelectric power generation is also because of unavailability of sun light in night and in cloudy weather. Also sun light varies time to time during a day. Over all the technique of producing electricity is not at all economical.

Energy of Sun Light

We can use sun light directly to produce electricity. This is done by PV CELL. Here, sunlight directly strikes on the surface of voltiac cell. The photovoltaic cells are basically semiconductor p n junction cells. The voltage appears across the junction of cell due to the incident sunlight. This potential difference creates electricity in the circuit connected to the solar panel system. Solar panels for producing electricity are becoming popular now days because of limitations of other conventional resources.

Energy of Wind

We can use wind power to generate electricity. Where sufficient wind is available for long periods of time, we can construct efficient wind power mill to produce electricity. Here the wind mill rotates an electrical generator. As the speed of wind is not fixed we should not use the electrical energy produced by wind mill directly to the load. Instead we charge a battery connected to the system. We feed the output of the battery to load through an inverter. The main advantage of the system is that it has very low running cost, because of zero fuel cost and negligible maintenance cost. The main disadvantages of the system are variable output, unreliable because of variable wind pressure throughout a day as well as throughout a year and production rate of electricity is also quite low compared to conventional sources of energy.

Energy of Water Head

When we obstruct the natural flow of water from upstream to downstream in a river by constructing a dam across the river, a head is created in this water. When we allow to flow this stored water in a controlled way through the dam the potential energy stored in this high headed water gets released in the form of kinetic energy. This kinetic energy rotates a water turbine. An alternator coupled with the shaft of the turbine generates electrical energy. The power plant which use water head to produce electricity are referred as hydroelectric Water power plant is the most acceptable source of electricity because it is clean, it does not cause pollution in atmosphere, it is simple in construction, it is robust and demands very less maintenances. In addition to these reasons, the dam helps irrigation in the localities and controls flood. But the construction of dam needs huge monetary investment and complex engineering. Another drawback of the system is that we can not construct a hydroelectric plant at load centre, we only can construct it in downstream river which may be far away from the load centre.

Energy of Fuel

Till date the fuels are the main source of electricity. We can use three types of fuel for the purpose. Solid fuel such as coal, liquid fuel such as diesel and gaseous fuel such as natural gas. Whatever may be the form of fuel that is either solid, or liquid or gaseous the basic principles is same in this system. Here heat generated due to combustion of fuel in the furnace creates steam by boiling water in a vessel called boiler. This steam is then allowed to expand through nozzles in a turbine. This creates kinetic energy on the turbine blades which turns the turbine shaft. The alternator coupled with the shaft of the turbine generates electrical energy. We refer this system of producing electricity as thermal power generating plant Although till date fuel is the main source of electricity generation but it has a limitation of availability in nature and it is true that the availability is diminishing day by day.

Energy of Nuclear

Nuclear fission releases a huge quantity of energy. This energy is used to produce steam which rotates a turbine coupled with an alternator. The alternator produces electrical power. In nuclear reaction the requirement of radio active material quite small for producing a large quantity of energy. Although the cost of nuclear fuel is quite high but till it is cost effective process of generating electrical energy since the quantity of nuclear fuel used in the process is very small. It is found that one kg of uranium (radioactive material that is nuclear fuel) is equivalent to 4500 kg of coal fuel. The plants where nuclear reaction is the source of energy for boiling water to produce steam  is called nuclear power station. The nuclear power plants do have two major drawbacks.

1. The establishment costs, maintenance costs and running costs of the plants are higher than that of other conventional thermal power generating plant .
2. The disposal of nuclear wastes is another big issue for nuclear power plant.