Saturday, August 29, 2020


The body of plants and animals are built by numerous cells. The structure of different organism is different. In case of human beings also there is difference structure between different races. The characters of organism is being transmitted from their ancestors from the beginning of development of organisms. The medium of transmission of heredity is called chromosome which is formed by numbers of gene. The genes are built by Deoxyribonucleic acid(DNA) molecules. Chromosomes not only carry hereditary characters but also some sex linked diseases like hemophilia.
Chromosomes and DNA
Deoxyribonucleic acid (DNA) is the genetic code that allows information to be transferred from one generation to the next. DNA molecules consist of two linear chains that are wrapped around one another forming a double helix structure. These helical structures are further wound into chromosome structures. Chromosomes are divided into two parts with a constriction point in the in the middle which is known as the centromere. The four types of chromosomes in animal cells are classified by the position of the centromere.
Structure and Function of the Centromere
Centromeres consist of a complex combination of proteins and DNA. They are essential to the division of cells and ensure the accurate segregation of chromosomes. Studies have demonstrated that chromosomes without centromeres segregate randomly and are eventually lost from cells. In contrast, chromosomes that have multiple centromeres can be subject to fragmentation.

Types of chromosome

Metacentric Chromosomes

Metacentric chromosomes have the centromere in the center, such that both sections are of equal length. Human chromosome 1 and 3 are metacentric.

Submetacentric Chromosomes

Submetacentric chromosomes have the centromere slightly offset from the center leading to a slight asymmetry in the length of the two sections. Human chromosomes 4 through 12 are submetacentric.

Acrocentric Chromosomes

Acrocentric chromosomes have a centromere which is severely offset from the center leading to one very long and one very short section. Human chromosomes 13,15, 21, and 22 are acrocentric.

Telocentric Chromosomes

Telocentric chromosomes have the centromere at the very end of the chromosome. Humans do not possess telocentric chromosomes but they are found in other species such as mice.

Uric Acid

Uric acid is a chemical formed when our body breaks down substances called purines. Purine is important to our body because it produces essential proteins. Uric acid is produced by our kidney braking down of purin. Uric acid is also useful to our body which cleanses blood vessels and toxic materials. If access of uric acid is formed it will be harmful to our body.
Factors that may cause a high uric acid level in our blood include:

  • Drinking too much alcohol
  • Genetics (inherited tendencies)
  • Hypothyroidism (underactive thyroid) (underactive thyroid)
  • Immune-suppressing drugs
  • Niacin, or vitamin B-3
  • Obesity
  • Psoriasis
  • Purine-rich diet — liver, game meat, anchovies, sardines, gravy, dried beans and peas, mushrooms, and other foods
  • Renal insufficiency (inability of the kidneys to filter waste)

Suymptoms and effects of high uric acid

  • If too much uric acid stays in the body, a condition called hyperuricemia will occur. Hyperuricemia can cause crystals of uric acid (or urate) to form. These crystals can settle in the joints and cause gout, a form of arthritis that can be very painful. They can also settle in the kidneys and form kidney stones.
  • If untreated, high uric acid levels may eventually lead to permanent bone, joint and tissue damage, kidney disease and heart disease. Research has also shown a link between high uric acid levels and type 2 diabetes, high blood pressure, and fatty liver disease.

Preventions of Uric acid

  • Drink sufficient amount of water
  • Avoid eating red meat, organ meat, dried seeds of peas and beans
  • Eat cherry fruit and green cucumber
  • Avoid alcohol
  • Avoid pork, mushroom and cauliflower



In our body glucose is formed from our food which is converted to energy by help insulin, a hormone made by the pancreas. If quantity of insulin formation decreases from its limit excess of glucose is stored on blood and the condition is called diabetes.
Symptoms of diabetes

  • Increase of hunger
  • Increase of thirst
  • Increase of urination
  • Wounds take long time to recover
  • Increase of tiredness
  • Blurred vision of eye

Prevention of diabetes

  • Loose the weight
  • Use balanced diet
  • Avoid smoking and drinking alcohol
  • Take green vegetables and fruits sufficiently
  • Avoid mental tension
  • Do morning walk or exercise

Blood Pressure

The pressure exerted by blood on the walls of blood vessel is called blood pressure. Blood pressure depends upon size of blood vessel, amount of blood in body, rate of flow of blood and frequency of heartbeat. Blood can flow on body due to pressure on blood. There are two conditions of blood pressure, one systolic and other diastolic.

Systolic blood pressure is that pressure when heart is compressed and blood exits from heart. For healthy person its value is 120 mm Hg but it ranges from 90 to 130 mm Hg for an adult person which may differ from person to person.

Diastolic blood pressure is that pressure when heart relaxes and blood enter into the heart. For an adult person its value ranges from 60 to 90 mm Hg. For healthy person its value is 80 mm Hg.

Causes of high blood pressure

  • Smoking regularly
  • Drinking of alcohol regularly
  • Obesity or overweight
  • Lack of physical exercise
  • Excess of salt on food
  • Age above 40
  • Tension on mind
  • Adrenal and thyroid disorder
  • Genetical cause

Prevention of high blood pressure

  • Avoid smoking and drinking alcohol
  • Avoid fat on food
  • Minimize amount of salt
  • Do physical exercise
  • Take part in yoga and meditation to avoid tension

Blood Circulation

There are mainly two types of blood circulation in human body

  1. Systemic circulation: The blood circulation between heart and different parts of body (except lungs) operated by arteries and veins is called systemic circulation. When left auricle contracts, blood flows out of heart via aorta, aorta divides to arteries which further subdivide to capillaries and pure blood reaches to cell level. After consumption of nutrients, minerals and oxygen, wastes are collected by veins and returned back to left auricle of heart. In this way systemic circulation continues.
  2. Pulmonary circulation: The blood circulation between heart and lungs operated by pulmonary artery and pulmonary vein is called pulmonary circulation. When right ventricle contracts blood flows from heart to lungs via pulmonary artery. The blood is purified inside lungs(Oxygenated) and returned back to left auricle of heart via pulmonary vein.

Blood vessels

 There are mainly three types of blood vessels in human body called Artery, Vein and Capillaries.

Artery:  Arteries carry blood from heart to other parts of body. Except pulmonary artery which passes blood from heart to lungs, carry pure blood. Arteries are formed by dividing aorta and further dividing of arteries arterioles are formed. Arterioles further divide into capillaries. Artery has thick wall and can hold large amount of blood pressure. Artery doesn’t have valve as blood in the arteries, after being pumped by the heart, are under much higher pressure than blood in veins so there is no need for valves in arteries to prevent back flow.

Vein: The blood vessels which carry blood from body to heart are called vein. They carry impure blood which is collected in heart and sent to lungs for purification. To prevent backflow of impure blood there is valve on vein.

Capillaries: They are very thin blood vessels connecting blood flow on cell level. They supply nutrients, oxygen and minerals to cell and collect back west products.


Human Heart

The heart is made up of cardiac muscle. The heart is a muscular organ about the size of a fist, located just behind and slightly left of the breastbone. The heart pumps blood through the network of arteries and veins called the cardiovascular system.  

The heart has four chambers:

  • The right atrium receives blood from the veins and pumps it to the right ventricle.
  • The right ventricle receives blood from the right atrium and pumps it to the lungs, where it is loaded with oxygen.
  • The left atrium receives oxygenated blood from the lungs and pumps it to the left ventricle.
  • The left ventricle (the strongest chamber) pumps oxygen-rich blood to the rest of the body. The left ventricle’s vigorous contractions create our blood pressure.

The coronary arteries run along the surface of the heart and provide oxygen-rich blood to the heart muscle. A web of nerve tissue also runs through the heart, conducting the complex signals that govern contraction and relaxation. Surrounding the heart is a sac called the pericardium.

Valves of heart: 

Human heart valves are remarkable structures. These tissue-paper thin membranes attached to the heart wall constantly open and close to regulate blood flow (causing the sound of a heartbeat). This flexing of the tissue occurs day after day, year after year. In fact, the tissue withstands about 80 million beats a year, or 5 to 6 billion beats in an average lifetime. Each beat is an amazing display of strength and flexibility.

The heart has 4 valves:

  • The mitral valve and tricuspid valve, which control blood flow from the atria to the ventricles
  • The  pulmonary valve controls blood flow from heart to lungs
  • The aortic valve controls blood to flow from heart to body

A  normal, healthy heart valve minimizes any obstruction and allows blood to flow smoothly and freely in one direction. It closes completely and quickly, not allowing any blood to flow back through the valve.

Composition of Blood

Blood is considered a fluid connective tissue because it has a matrix. The living cell types are red blood cells(RBC), also called erythrocytes, and white blood cells(WBC), also called leukocytes. The fluid portion of whole blood, its matrix, is commonly called plasma.  

Plasma: Plasma occupies 55% of blood of which 90% is water and remaining 10% is protein, fats and carbohydrate. Plasma is yellow in color. Plasma is designed to carry nutrients, hormones, and proteins to the different parts of the body. It also carries away the waste products of cell metabolism from various tissues to the organs responsible for detoxifying and/or excreting them. In addition, plasma is the vehicle for the transport of the blood cells through the blood vessels.  

Red Blood cells(RBC): RBC are deep red in color and biconcave in shape. The don’t have nucleus. The red color is due to the presence of hemoglobin. They are formed in bone marrow. They have life span of 90 to 120 days. After that they are destroyed on spleen. To supply oxygen on body is major function of RBC. Due to lack of RBC in bood there will be problem on supply of oxygen and the disease called anaemia occurs.

White blood cells(WBC): WBC are colorless and don’t have fixed shape but they have nucleus. WBC are larger than RBC. If the number of WBC exceeds than limit a disease called leukemia occurs. WBCs, also called leukocytes, are an important part of the immune system. These cells help fight infections by attacking bacteria, viruses, and germs that invade the body. White blood cells originate in the bone marrow but circulate throughout the bloodstream.

Platelets: Platelets are also called trombocytes. They are very tiny cells with no neuleus. They are formed in bone marrow and have life span of 2 to 3 days.they help blood clotting on wounds and fight against disease.


Honey Bee

Honey bee are highly social and laborious insects. Honey bee belongs to the phylum Arthropda. It is very useful insect as it produces honey and also plays the role in pollination of flower. The collect flower nectar on their hive and produce honey. They live in colony with strict discipline. Organizationally there are three types of hone bee in a hive, the are

  1. Queen bee. Inside a hive there is a largest and most shiny bee called queen bee. Queen bee mates with drone bee and lay eggs. Queen bee generates special smell and all other bees identify their hive with that smell. During matting period queen bee comes out of hive mates with drones on air which  is called matting flight or nuptial flight.
  2. Dron bee: Drone bee is smaller than queen bee and larger than worker bee. Its body is covered with hair. They don’t have honey gland and can’t take food themselves. They are feed by worker bees. The only their duty is to matt with queen bee.
  3. Worker bee: It is smallest in size and they in largest numbers. They collect nectar from flower, fight with enemy, protect larva, make hive and feed for drone bee.

Life cycle of honey bee

Egg Stage:

Queen bee is the only bee in the colony who is capable of laying about 2,000 to 3,000 eggs in one day. The egg is positioned upright and falls on the side by the third day. The queen bee lays both fertilized egg and unfertilized egg. The fertilized egg develops into female bees or queen bees. The unfertilized egg hatches and male bees are born; also known as drone bees.

The Larval Stage:

The difference between a worker and the queen bee is made three days after the egg transforms into larvae and six days after the egg is laid in the beehive. The “royal jelly” is fed to all the larvae, i.e., the female bees, the workers and the drone bees during their initial three days as larvae. The larva sheds skin multiple times throughout this stage. Later, the royal jelly is fed only to the female larvae, which eventually becomes a queen bee. Finally, the worker bees cover the top of the cell with beeswax to protect and facilitate the transformation of the larvae into a pupa.

The Pupa Stage:

Here the bee has developed parts like wings, eyes, legs and small body hair that physically appears close to an adult bee.

The Adult Stage:

Once the pupa is matured, the new adult bee chews its way out of the closed-cell. The queen bee takes 16 days from the egg stage to form into an adult. The worker bee takes 18 to 22 days for complete development, and drone bees take 24 days to develop into an adult bee.


 Silk worm or silk moth, is an insect from the moth family Bombycidae. It is the closest relative of Bombyx mandarina, the wild silk moth. The silkworm is the larva or caterpillar of a silk moth. It is an economically important insect, being a primary producer of silk. A silkworm's preferred food are white mulberry leaves, though they may eat other mulberry species and even the osage orange. Domestic silk moths are closely dependent on humans for reproduction, as a result of millennia of selective breeding. Wild silk moths are different from their domestic cousins as they have not been selectively bred; they are thus not as commercially viable in the production of silk.

1. It is otherwise called “Bombyx” and produces silk, It is reared on mulberry leaves.

2. The body is divisible into head, thorax and abdomen. The abdomen is short and stout.

3. The colour is creamish white, the antennae are short and plumose and mouth parts are of sucking type.

4. The two pairs of wings are always held horizontally when the moths are in resting position.

5. The sexes(male and female) are separate and life history is completed through a larval stage the caterpillar or silk worm and a pupal stage – the chrysalis. The female lays about 400 eggs at a time and dies after laying eggs.

 Life cycle:


Egg is the first stage of a silkworm’s life cycle. The female moth lays an egg about the size of an ink dot during summer or the early fall. The egg remains in dormant stage until spring arrives. The warmth of the spring stimulates the egg to hatch. The egg of Bombyx mori is a very small and hard structure; about the size of a pin head and resembling a poppy seed. The egg shell provides a protective covering for embryonic development. When first laid, an egg light yellow. A fertile ovum darkens to a blue-gray within a few days.



The larva is the vegetative stage where growth takes place. The larva of Bombyx mori, commonly called a silkworm, is host specific to mulberry. During growth, the larva molts 4 times. The period between successive molts is called an instar. The silk worm, upon hatching, is about 1/8th of an inch and extremely hairy.


Young silkworms can only feed on tender mulberry leaves. However, during the growth phase they can eat tougher mulberry leaves as well. The larval stage lasts for about 27 days and the silkworm goes through five growth stages called instars, during this time. During the first molting, the silkworm sheds all its hair and gains a smooth skin.



As the silkworm prepares to pupate, it spins a protective cocoon. About the size and color of a cotton ball, the cocoon is constructed from one continuous strand of silk, perhaps 1.5 km long (nearly a mile). The silk cocoon serves as protection for the pupa. Cocoons are shades of white, cream and yellow depending on silkworm genetics. After a final molt inside the cocoon, the larva develops into the brown, chitin covered structure called the pupa. Metamorphic changes of the pupa result in an emerging moth

If the silkworms are allowed to mature and break through the cocoon, the silk would be rendered useless for commercial purposes. So the encased insect is plunged into boiling water to kill the inhabitant and dissolve the glue holding the cocoon together. The end of the silk is then located and the cocoon unwound onto a spindle to be made into thread.


Cocoon is the stage in which the larva spins silk threads around it, to protect itself from its predators. The larva traps itself inside the cocoon in order to pupate. The color of the cocoon varies, depending upon what the silkworm eats. It can range from white to golden yellow. The second molting occurs inside the cocoon, when the larva turns into a brown pupa. It takes about 2-3 weeks for the pupa to metamorphose into an adult moth.



The adult stage completes the life cycle of Bombyx mori. It is the reproductive stage where adults mate and females lay eggs. Moths are flightless and lack functional mouth parts, so are unable to consume the food/nutrition.

Once the adult moth comes out of its cocoon, its only purpose is to find a member of the opposite sex, and mate. Males are larger than females and more active. They flap their wings rapidly to attract the females. Within 24 hours of mating, the male moth dies, while the female lays abundant eggs, after which it dies as well. There on, a new silkworm life cycle begins.

Features of silk

  • Silk is strong and shiny fiber
  • Silk fiber has high elasticity
  • Silk clothes can be worn on all seasons
  • Silk is longest natural fiber
  • Silk fiber lasts for long time

Importance and uses of silk

  • Silk is used to make clothes and curtains
  • Silk is used to make synthetic fiber by mixing it
  • Silkworm larva are used as food also
  • Cultivation of silk improves economy

Friday, August 28, 2020

Compost and Chemical Fertilizer

Compost  Fertilizer: Compost is organic matter that has been decomposed in a process called composting.
This process recycles various organic materials otherwise regarded as waste products
and produces a soil conditioner (the compost).

Compost is rich in nutrients. It is used, for example, in gardens, landscaping, horticulture, urban agriculture and organic farming. The compost itself is beneficial for the land in many ways, including as a soil conditioner, a fertilizer, addition of vital humus or humic acids, and as a natural pesticide for soil. Compost is useful for erosion control, land and stream reclamation, wetland construction, and as landfill cover. Compost is either prepared by decaying soft plants on pit or from animal manure. The advantages of compost fertilizers are

  • Provide humus in soil
  • Act as natural insecticide for soil
  • Preserve humidity of soil
  • They contain most of all nutrients needed for plants

  • Maintain acidity of soil
  • No environmental pollution
  • No harm to microorganism in soil


  • Heavy and nuisance for transport
  • Long term process of formation
  • Expensive compared to chemical fertilizer

Chemical fertilizer: The fertilizers prepared from chemical process by use of different minerals is called chemical fertilizers.

  • Nitrogen fertilizer: Ammonium nitrate, Ammonium sulphate and urea are known as nitrogen fertilizers.  Nitrogen fertilizers help plant to grow their tissues, protein synthesis and photosynthesis. Due to lack of nitrogen in soil plant leaves turn to yellow, flower and fruit become small and premature fall.
  • Phosphorus fertilizer: ammonium phosphate, super phosphate and triple phosphate are examples of phosphorus fertilizers. It helps plant to develop fruit and seed properly.
  • Potassium fertilizer: potassium chloride, potassium nitrate and potassium sulphate examples of potassium fertilizers. Potassium help protein synthesis and photosynthesis in plants.

Chemical fertilizers are cheaper and easier to transport than organic fertilizer but they have following drawbacks

  • Pollution is created on air, water and soil
  • Depreciation of fertility of soil
  • Rivers and streams are polluted and aquatic animals are affected
  • Unwanted weeds are grown heavily
  • Ecosystem is affected

Soap and Detergent

 Soap is a salt of higher fatty acid obtained from the reaction of oil or fat with alkali. Soap is a cleanser used in daily life for washing clothes and our body parts. The process of making soap from oil or fat by reaction with alkali is called saponification. In general soap is formed by following chemical reaction.

For bathing purpose high quality vegetable oils are used to make soap such as olive oil, coconut oil etc and for washing purpose animal fat is used. If sodium hydroxide(NaOH) is used with oil of fat solid soap or hard soap is formed. Instead of NaOH, if potassium hydroxide(KOH) is used for saponification liquid soap of soft soap is formed such as shampoo and saving cream. If soap is dissolved in alcohol and vaporized transparent soap is obtained.

Qualities of good soap

  • Bubbly- this give the soap ability to lather.
  • Cleansing - the ability of the soap to trap the dirt on the skin and wash it away.
  • Hardnes-the frimness of the soap bar.
  • Conditioning- the amount of moisture that is left on the skin.
  • Creamy- this measure the stability and creaminess of the soap lather.
The Detergent: Detergents are substance obtained from hydrocarbons used for cleansing clothes. They are more soluble than soaps.They are also called soapless soap as they clean clothes as soap but chemical nature is very different from soap. Sodium lauryl sulphate, alkyl benzene sulphonate and sodium pyrophosphate are example of detergent.


 Plastic is an artificial polymer which can be changed to any shape. The word plastic is driven from greek word “plastiko” which means changeable shape. Raw material to make plastic is obtained from crude mineral oil.

Monomer:  Monomer is  a molecule of any of a class of compounds, mostly organic, that can react with other molecules to form very large molecules, or polymers. The essential feature of a monomer is polyfunctionality, the capacity to form chemical bonds to at least two other monomer molecules.

Polymer:  polymer is a large molecule made up of chains or rings of linked repeating subunits, which are called monomers. Man made  polymer is called plastic.

Polymerization:  Polymerization is a chemical reaction in which two or more molecules combine to form larger molecules that contain repeating structural units.

Plastics are mainly of two types:

1.  Thermoplastic: The plastic which melts on heating and reshaped and reused again is called thermoplastic. Polythene, polyvinyl chloride(PVC), polystyrene etc are examples of thermoplastic.

2. Thermosetting Plastic: thermosetting plastic is a polymer that irreversibly becomes rigid when heated. Such a material is also known as a thermoset or thermosetting polymer. Initially, the polymer is a liquid or soft solid. Thermosetting plastics cannot be remolded and reused. Bakelite is an example of thermoplastic which is used to make heat and electric insulators.

Features of Plastics

Lightweight with a high strength-to-weight ratio

Can be manufactured inexpensively and mass produced

Water resistant

Shock resistant

Thermally and electrically insulating

 Uses of plastics

1. Making Plastic utensils and furniture

2. polythene bags

3.making heat and electric insulators

4. making artificial fiber to to make clothes


A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing a nonmetallic mineral, such as clay, at a high temperature. Common examples are earthenware, porcelain, flower vase and brick.

The soil used to make clear white ceramic is called kaolin. To prepare ceramic mud is finely powdered using ball mill, mixed with water and converted to shape of vessel. The shaped mud is dried on mild sunlight. Then it is heated on furnace at suitable temperature. To make it non porous and shiny common salt powder is spread on heating. This process is called glazing. After that they are colored to make more attractive. Ceramics are non porous and so used make cup plate and other utensils, electric insulator, floor tiles, and even artificial joints and teeth. As they do not react with acid, base salt and other solvant the can be used to make vessel storing them


Glass is a hard, transparent and brittle material with nature of super cooled liquid. On glass formation process it is cooled to below its melting point and then solidifies. Glass on windows after long time becomes slightly thicker at bottom part as glass molecules move down very slowly under gravity. Main raw material of glass is silica(SiO2). And the main source of silica is sand. Let’s discuss about some types of glass here.

1.  Silica Glass: Silica is heated to 1600oC to melt it and cooled down to form silica glass. It is used to make laboratory apparatus and electrical appliances.

2. Water Glass: Water glass is formed by heating silica with Sodium Carbonate or Potassium Carbonate at 800oC.  It is called water glass as it is slightly soluble in water. This glass is used to make silica garden.

3. Ordinary Glass: This glass is formed by heating 50% Silica, 15% Sodium Carbonate, 10% Calcium Carbonate and 25% old glass pieces at temperature of about 850oC. Bottles, windows glass and many other general purpose glass is made from this glass. This glass is also called soft glass and soda lime glass.

4. Hard Glass or Soda Lime Glass: This glass is prepared by heating potassium Carbonate and Calcium Carbonate with silica. It has high melting point and used to make hard glass test tube and othe laboratory apparatus.

5. Borosilicate Glass or Pyrex Glass: It is formed by heating sodium carbonate, calcium carbonate and boric oxide with silica. This is used to make heat resistive lab apparatus

6. Lead crystal Glass: This glass is formed by heating potassium carbonate and lead monoxide with silica. Mostly it is used to make lenses, spectacle glass etc as it has high refractive index.

To make coloured glass we have add some metal oxide on heating process.


A cement is a binding material, a substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand, steel rod and gravel together. Cement mixed with fine aggregate produces mortar for masonry, or with sand and gravel, produces concrete. Concrete is the most widely used material in existence and is only behind water as the planet's most-consumed resource. Making procedure: First of all lime stone is crushed to about 2cm size and clay is mixed on 2:1 ratio. The mixture is grounded to fine powder and slurry is formed by mixing water. The slurry is lifted to tower and slowly comes down via rotating kiln. The slurry is slowly heated with coal upto 1300-1600oC of temperature. Due to this cement clinker is formed. After cooling of clinker, it is grounded in grinder with mixing about 2.5% of gypsum. Now cement is ready.

Uses of cement:

Following are the different uses of cement in construction works:

1. To prepare cement mortar

2. To prepare cement concrete

3. To build fire proof and thermal proof structures

4. To build hydrographic and frost resistant structures

5. To build chemical proof structures

6. As a grout material

7. To construct Cement concrete roads

8. To manufacture precast members

9. For aesthetic concrete construction

Electric Energy Consumption

 Electric Energy Consumption is calculated from electric meter installed by electricity authority at our

home. This meter measures electric energy in kilowatt hour. For our convenience 1 Kilowatt hour is said to be 1 Unit. The cost of 1 Unit electricity is same all over the country and differs from country to country. Thus to calculate energy consumption we need following data.

Electric power in kilowatt, time in hour and to calculate amount to pay we need rate per unit of electricity.

Q. If a heater of 1,200 watts is used daily for 30 minutes what is monthly power consumption? How much will be electricity bill if per unit we have to pay Rs.12?

Here, Power(P) = 1,200 watts = 1,200/1,000Kw = 1.2 Kw

Time of consumption per day = 30/60 = 0.5 hours

Total Time of consumption(T) = 0.2 x 30 =15 hours

So, energy consumption = P x T = 1.2 x 15 = 18 units

Amount to pay = consumption x rate  = 18 x 12 = Rs.216.

Q. At a home there are 5 bulb of 60W used daily for five hours and one iron of 1,000W used daily for an hour. What monthly bill should be paid with the rate of Rs. 10 per unit?

Here, for bulbs,

 P = 5 x 60 = 300W =300/1000 = 0.3 Kw

T = 5 x 30 =150 hrs(Monthly)

Consumption = P x T = 0.3 x 150 = 45 units

For Iron, P = 1,000W = 1Kw

T = 1hr x 30 = 30 hrs(Monthly)

Consumption = P x T = 1 x 30 = 30 units

Total consumption = 45 + 30 = 75

Rate = Rs. 10 per unit

So, total bill = consumption x rate = 75 x 10 = Rs. 750


Transformer is a passive electrical device used to increase or decrease AC voltage. It is based upon principle of electromagnetic induction. There are two coils on transformer. The coil on which power in fed is called primary coil and that one from which output power is taken is called secondary coil. Both coils are wound on laminated iron to reduce loss of electric energy by heating due to eddy current. Transformer cannot change the voltage of DC current. There are two types of transformers regarding to voltage level

  • Step Up Transformer: It is used to increase voltage of AC current. In step up transformer number of turns on secondary coil is greater than that of primary coil.
  • Step down Transformer: It is used to decrease the voltage of AC current. In step down transformer number of turns in primary coil is greater tha that in secondary coil.


Transformer Formula

The value of the power for an electric circuit is the value of the voltage by the value of the current intensity. As in the case of a transformer, the value of the power in the primary is the same value for the power in the secondary we have:

(input voltage on the primary coil) × (input current on the primary coil ) = (output voltage on the secondary coil ) × (output current on the secondary coil)

This can be written as an equation:

Vp × Ip = Vs × Is

We can also work out the transformer output voltage if we know the input voltage and the number of turns on the primary and secondary coils.

inputvoltageontheprimarycoiloutputvoltageonthesecondarycoil                          = numberofturnsofwireontheprimarycoilnumberofturnsofwireonthesecondarycoil

This can be written as an equation:

VpVs = npns


Vpinput voltage on the primary coil.
Vsinput voltage on the secondary coil.
Ipinput current on the primary coil.


Isinput current on the secondary coil.
npthe number of turns of wire on the primary coil.
nsthe number of turns of wire on the secondary coil.