Audio frequency

Audio frequency is frequency which can be heard by human or animals. Its range is 4k hz to 20khz. All humans and animal which have audible sound have frequency of voice in this range. The voice, which have more or less frequency than this range it can’t be heard.

In telecommunication transmission is done in high frequencies for fast transmission. These messages or data is then converted to audible frequency for hearing. As like television when its data is transmitted, it is in high frequency but when television set receive and decodes the data and convert it to visible and audible messages. it produces audible message in range these frequencies. So it is called audio frequency.

Apparent power

Apparent power is electrical power summed up of two powers, real power and reactive power. Real power is power which is actually  used by devices , machines, instruments etc in form of heat or magnetic field. it also can be used in other farms as storages like batteries, capacitors, inductors etc.

AC power has two components real power and reactive power. Apparent power is power which appears on the terminal of ac load like motors mostly.  Apparent power is measured in VA,KVA MVA. All the generators are rated in KVA , VA or MVA. Apparent power is sum of reactive and real powers. Reactive power is always present but it is not used. Reactive power is always transmitted back to the system or generator while real power is used by the load. All inductive load or lagging power factor loads transmits reactive power back to the system.

Only resistive load like lights or heaters etc don’t use reactive powers but real power.

In figure you can see the apparent power, real power and reactive power. Real power is also called Active power and True power. Real power is measured in KW and denoted by S. Reactive power is measured in KVAR,VAR,MVAR and denoted by Q

Analog-to-digital converter

Analog to digital converter is electronic circuit which  make analog signal digital. in other words we can say that ADC is basic and very important circuit in modern era of life. when we speak ,microphone  produce analog signal. this signal is then amplified and then before transmission, it is converted to digital form.

Analog signal is continuous signal as like sine wave, sawtooth wave etc while digital signal is discrete signal in the form of 1 and 0. Any of the input or analog signal is converted to digital if transmitted. There are a lot of methods to convert the analog signal into digital form. Mostly used methods are comparators. In comparator one reference voltage is given while on other terminal signal is provided. This comparator gives output if signal voltage is greater or equal to the reference as 1 and 0 vice versa. Here also keep in mind that resolution of digital signal is also important. It mean the signal you are converting into digital form, how many bits signal do you want. one bit, 2 bit,4bit,8bit,16bit  32 bit 64 bit etc. Now a days laptop and window are operation on 64 bit processors.

Amplitude modulation

Modulation is method to impose signal on carrier frequency. There are many methods to do this. Amplitude modulation is one of those methods. In this method signal and carrier frequency are mixed in such a way that amplitude of carrier frequency changes according to signal. This is very old method. In this method there is a lot of noise. in simple it is also called AM modulation. Its range according to other methods is long for transmission but there is lot of noise which is added automatically. It circuit and working is very simple. it is shown in figure.

Keep in mind when amplitude modulation is done there are two signal bands. One upper side band and other lower side band. One of these bands are transmitted some time both of the bands are transmitted and in receiver one band is suppressed and  other is demodulated to get signal. In old system of radio there was AM modulation used. Now it is also used but very rarely.


Its is a process in which components are separate on basis of size ,shape, length, density ( in other words its is a separation process of material).its is a machine which is use in science laboratory such as biotechnology lab.

in this apparatus DNA ,RNA, amino acids and protein are separated by plant or animals cell or tissue (bacterial genetic material also be separated).


Its works on density of components desire to separate in form of homogeneous solution


F=intensity of centrifugal force

M= Mass of particle

w= angular volecity of rotation

r=distance of migrating particle from center of axis of rotation

Types of Centrifuge:

1.small bench top centrifuge:

a).in this centrifuge without chill solution can be separated.

b).blood ,serum .etc are separated

c).slow in speed upto 4000 rpm

d).100 eppnodroff tube are can be  loaded in a time.


2.Micro Centrifuge:

a).2mm volume of eppnodroff tube

b).10,000 eppnodroff tube can be loaded

c).protein are separated

3.High speed centrifuge:

a).50,000 eppnodroff tube are loaded

b).sub.organelles are separated

c).17000 rpm speed

4.ultra high speed centrifuge:

a).90,000 eppnodroff tube are loaded.


b).chilled material are used

c).microorganisms are separated

  • Rotar in centrifuge
  • Fixed rotar

horizontal solution are in rotation and clearly pellets are separated debris are obtain

  • swimming bucket rotar

its solution in vertical position in rotation and no clearly pellets are separated

Power Amps:

Power Amplifier is electronics circuit which amplify the signal. In other words amplifier is circuit or electronic device which make week signal strong. Amplifier is an essential part of mostly used devices like, mobile , Television, Audio amplifier, CD players, tape recorders etc. In other words amplifier is important part of any system, transmission system or any other. The main        part of the amplifier is transistor an electronics  component which amplify the signal. any signal which is amplified in micro volt or amps and output is in few amps. It is said that amplifiers can amplify signal up to 1000s of times, it is true. but keep in mind it cannot be 1 volt to 1000 volt but it can be from 1u volt to 1 volt which is million times amplified.

How Amplifier works:

The working of amplifier is as we week signal is applied on the base of the transistor it makes changes in current or voltage flowing from emitter to collector of transistor. Thus voltage measure on the resistor which is connected at collector in series, is high. it is called that signal applied on base of transistor is amplified. The value of resistor in series with collector is always high rather than resistance of emitter. These resistances actually cause amplification of signal. look at figure:


Ampere is international  unit for current. The flow of charges is called current. if one coulomb charge flow in one second then it is called one ampere of current. ampere is not coulomb but coulomb per second. it is denoted by A or amp. in consumption  Ampere is  as: A=V/I   this is called ohm’s law. this will be discussed in next article.The batteries are rated in AH Ampere- Hours. This means how much current a battery can provide for one hour. this is ideal condition.


The term ampacity comes from ampere  capacity. this means capacity of amperes of a wire which it can carry. Proper definition we can make is the ability of any wire to carry out the current in amperes is called ampacity of that wire.The ampacity of wires changes with size and voltage and also material of wires. Copper wires have more ampacity than aluminum or any other metal.


Ammeter or Ampere meter is instrument which measures quantity of current in closed loop. in other words ammeter is device which measures the current of load or line. The ammeter now a days comes in multi meter as a option. The old multi meter or ammeter was analog which told the quantity of current by moving a needle to respective value of current. Now a days it is era of digital world so multi meter or ammeter also are available in digital which show value in figures. these kind of meters are very accurate rather than analog meters.

Working of Ammeter:

The analog meter had scales rated over the different values and a needle indicated the  value by moving over the scale according to value of current. there are two resistances in parallel of a ratio difference. when current passed throw the resistance and then from coil of needle to move it which moves over scale to indicate the value. In modern era digital meter show value in figures. these meter covert analog signal in digital form by ADC “Analog to Digital Converters”. and then scan over LCD or 7 segment display.


Science is not a magic. it always exists in nature and scientists or engineer only make them usable or visible by machines. same like this electricity is not magic, it is also produce one of the nature quality which states” when a conductor is moved in magnetic field , there is potential difference on conductor  end” this phenomena is used in alternator or AC generator. when a conductor “armature” is rotated in magnetic field it produces potential difference of voltage which cause to move charges from one end to other of closed loop. these moving charges are called current.


Alternator is second name of electrical generator. it produces the alternating voltage and current.  These generators are rated in mostly KVA. it consists of two major parts, engine and generator. The engine rotates the shaft of alternator and alternator produces the electricity which is collected on its terminals. The alternators are of 2 basic types. Single phase and Three Phase alternators. Single phase alternators produce single phase electricity and three phase produce three phase electricity