Electric Charge

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The branch of physics which deals with the study of charges at rest, the force between them, fields and potential due to these charges. It is called Electrostatics or static electricity or frictional electricity.

Electric Charge

The charge is something possessed by a material object that makes it possible for them to exert electrical force and to respond electrical forces. The property of protons and electrons which gives rise to an electric force between them is called electric charge. It is a scalar quantity and its SI units is coulomb (C).

Types of Charges

There are two types of charge
  1. Positive charge
  2. Negative charge
An object can obtain positive charge by losing electrons while other can attain negative charge by gaining electrons. Charge always resides on the surface of the charged conducting object. An object can be charged by different methods like friction and induction. The proton possesses the positive charge. The electron possesses the negative charge (-e).

e = ±1.6 x 10-19

Properties of Electric Charge

  1. Two like charge repel each other, while two, unlike charge, attract each other.
  2. Electrification by friction can be explained on the basis of the transfer of electron. Charges are always distributed on the surface of the conductor.
  3. If a car is struck by lightning, persons sitting inside the car are shielded from the electricity and not harmed at all, since, all the charges remain on the outer surface and move to the ground through the lowest metallic part of the car.
  4. Charge is invariant (i.e., charge does not change with change in velocity)
  5. A charged body attracts lighter neutral body.
  6. Electric charge is additive (i.e., the total charge on a body is the algebraic sum of the charge present in different parts of the body). e.g., if a body has different charges as +2q, +4q, + -3q, –q, then total charge on the body is +2q.
  7. During any process, the net electric charge of an isolated system remains constant (i.e., conserved). In simple words, the charge can be neither created nor destroyed.
  8. Charge on a body can only have some particular values, this property of charge is called quantization of charge. The charge on a body always occurs in an integral multiple of charge on one electron (e).

Charging by induction

In charging by induction, a charged body imparts to another body some charge of opposite nature without any actual contact between them. In this process, the charging body does not lose any charge as it is not in contact with the charged body. Thus, we can say that induction is a process when the charge on a body is rearranged under influence of a nearby charged body (not in contact).

Coulomb’s Law

It states that two stationary point charges attract or repel each other with a force which is directly proportional to the product of the magnitude of charges and inversely proportional to the square of the distance between them. Consider two point charges q1 and q2 placed at a distance r from each other, then force between them is

F ∝ q1q2/r²

or

F = q1q2/4πεor² = 9×109×q1q2/r²

where the term 1/4πεo is called dielectric constant of the medium and εo(=8.85×10-12–¹²C²/N-m²) is called absolute permittivity of free space. If there is another medium between the point charges except for air or vacuum, then εo is replaced by εo,εr which is known as relative permittivity of the medium.

Transpiration, Guttation biology Definition

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Loss of water in the vapor state from the aerial parts of plants is known as transpiration. 98-99% of water absorbed by a plant is lost through transpiration. Most of the transpiration occurs through leaves and is called foliar transpiration. Stomata are tiny pore complexes, which occur on the soft aerial parts of the plants, especially the leaves. They hardly occupy 1-2% of the leaf surface, but due to perimeter diffusion, the exchange capacity of stomata is very high – almost equal to the whole surface area of the leaf. Each stoma is surrounded by two small specialized and differentially thickened guard cells. Guard cells contain chloroplasts while the same are absent from other epidermal cells.

Amount of Transpiration:

Due to transpiration 98 – 99% of absorbed water is lost. Only 0.2% is employed in photosynthesis. Rest is used for growth.

Psychrometer

An instrument for measuring atmospheric humidity as well as an amount of water transpired.

Percentage of various modes of Transpiration :

(i) Stomatal Transpiration: 50 – 97% of the total. (ii) Cuticular/Epidermal Transpiration: Ordinarily 3 – 10% but in herbaceous mesophytic plants, it may be up to 50%. (iii) Lenticular Transpiration: 0.1%. (iv) Bark Transpiration: 0.5%

Relative Humidity and Stomata:

Stomata remain open at R.H. above 70% and close below R.H. of 50%.

Transpiration on Hills:

High due to lower atmospheric pressure but low due to lesser hours of light and lower temperature. Transpiration is, therefore, near average but the plants show xeromorphy due to lesser water availability.

Turgor Changes in Guard Cells:

Schwendener (1881) was the first to point out that stomatal opening and closing is due to turgor changes in guard cells.

CO2 and Stomata:

Low CO2 concentration induces stomata to open. High CO2 level causes stomatal closure.Photoactive Stomata: Stomata open in response to light.

Photoactive Stomata

Stomata open in response to light. The action spectrum consists of red and blue light (blue light is more effective in the stomatal opening). Since most of the transpiration is stomatal. The action spectrum of transpiration is red and blue light.

Wilting

It is a loss of turgidity and drooping of leaves and other soft aerial parts of the plant due to the rate of water absorption being less than the rate of water loss in transpiration. Rapid absorption of water during daytime for meeting requirement of transpiration produces water deficit around the rootlets.Factors Influencing Transpiration:

Factors Influencing Transpiration:

(i) Light increases transpiration through the opening of stomata and increased protoplasmic permeability. Solar radiations also increase temperature which simulates more loss of water. (ii) Temperature: Increase in temperature increases transpiration. (iii) Humidity: Increase in moisture decreases transpiration and vice versa. (iv) Wind (Air movement): Air movement increases the rate of transpiration by bringing dry air and removing moist air from the transpiring material. High-velocity wind, however, closes stomata. (v) Atmospheric Pressure: Low atmospheric pressure increases transpiration. (vi) Availability of Water: The water availability influenced the transpiration. Reduced availability of soil water causes Wilting or loss of turgidity causing their drooping and rolling. (vii) Leaf or Transpiring Area: Reduction in leaf area reduces transpiration as in succulents, cacti, and euphorbia. (viii) Root/ Shoot Ratio: Higher root/shoot ratio has higher transpiration. (ix) Stomata: Sunken stomata reduce transpiration. Stomatal opening and number have the direct effect on transpiration. (x) Hair: They minimize transpiration. (xi) Cuticle: Transpiration is lower with the increase in thickness of cuticle.

Guttation definition biology

Loss of water in the liquid state from uninjured parts of plants. It usually occurs from tips and margins of leaves during the night or early morning when there is high atmospheric humidity as during wet seasons. Guttation occurs in some plants only (345 genera), e.g., Cucurbits, Potato, Tomato, Garden Nasturtium, Colocasia and other aroids, many kinds of grass. Photometer: It is an instrument for measuring the rate of transpiration by shoots through measuring the speed of their water absorption. Pyrometer: An instrument that gives a rough idea about the degree of stomatal opening

Gravitation

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Gravitation
Gravitation is defined as the non-contact force of attraction between any two bodies in the universe (no matter how far the bodies are). The earth attracts (or pulls) all the bodies towards its center. The force with which the earth pulls the bodies towards it is called the gravitational force of the earth or gravity of the earth.

Characteristics of Gravitational Force

  1. Gravitational force is action at a distance force i.e., it does not need any contact between the two bodies.
  2. It is a force between two bodies form action-reaction pair i.e., the force exerted by two bodies on each other are equal in magnitude and opposite in direction.
  3. Gravitational force is the weakest force in nature.
  4. It is 1036 small than electrostatic force and 1038 times smaller than nuclear force.
  5. Gravitational force is a constant as well as conservative force.
  6. The Gravitational force between two small bodies is very small. On the other hand, the gravitational force between two large bodies (say, the sun and the earth) is large.
Gravitational force is an inverse square force because it is inversely proportional to the square of the distance between the two bodies.

Universal law of Gravitation (Newton’s Law)

The universal law of gravitation was given by Newton. According to this law, the attractive force between any two objects in the universe is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. Consider two bodies A and B having masses m1 and m2, whose centers are at a distance r from each other.

Gravitational Force, F ∝ m1m2/r²

F=Gm1m2/r²

where G is universal gravitational constant. The value of G is 6.67 x 10-11 Nm2kg-2 and dimensional formula of G is [M-1L3T-2]. The law of gravitation is applicable for all bodies, irrespective of their size, shape, and position. Importance of Universal Law of Gravitation Universal law of gravitation successfully explained several phenomena like i) The force that binds us to the earth ii) Motion of the moon around the earth iii) Presence of atmosphere around a planet  

Sources of Energy

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Sources of Energy
Any system which is capable of providing useful energy in a convenient form at a steady rate over a long period of time.

Classification of Sources of Energy

Renewable Sources of Energy

These are the sources of energy which are being produced continuously in nature. These are inexhaustible e.g., solar energy, wind energy, hydro energy, biofuels (wood, biogas) hydrogen energy from the ocean (tidal energy, sea waves energy, ocean thermal energy). Advantage of renewable sources of energy are
  1. These sources will last as long as the earth receives light from the sun.
  2. These sources are freely available in nature.
  3. These sources do not cause any pollution.

Non Renewable Sources of Energy

These are the sources of energy which have accumulated in nature over a long time and cannot be quickly replaced. These sources of energy will be exhausted one day e.g., fossil fuels such as coal, petroleum, natural gas, fissionable materials. These are also called conventional sources of energy. Disadvantages of non-renewable sources of energy are
  1. Due to their extensive use, these sources are depleting fastly.
  2. It is difficult to discover and exploit new deposits of these sources.
  3. These sources are the major cause of environmental pollution.

Fuel

It is a source of energy used for different household and commercial purposes. e.g., coal, LPG, biogas, CNG, etc. Features of an ideal or a good fuel are
  1. It should have a high calorific or heat value so that it can produce maximum energy by low fuel consumption.
  2. It should have a proper ignition temperature so that it can burn easily.
  3. It should not produce harmful gases during combustion.
  4. It should be cheap in cost and easily available in plenty for everyone
  5. It should be easy to handle and convenient to store and transport from one place to another.
  6. It should not be valuable to any other purpose than as a fuel.
  7. It should burn smoothly and should not leave much residue after its combustion.
   

Energy

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Energy
Energy is measured as the capacity to do a work. It is a scalar quantity having SI unit same as the work i.e., joule (J) and CGS unit is erg. A larger unit of energy is kilojoule. An object having energy can exert a force (and hence do a work) on another object. Where it happens, energy is transferred from former object to latter object. The energy and power do not mean the same, these are different. Energy refers to the total amount of work done while power determines the rate of doing work.

Different Forms of Energy

Energy can manifest in several forms. 
  1. Heat Energy. The energy possessed by a body due to its temperature
  2. Internal Energy. The total energy possessed by a body by virtue of particular configuration of its molecules and also their random motion
  3. Electrical Energy. The energy required to maintain the flow of current in an electric appliance
  4. Chemical Energy. The energy absorbed or released during a chemical reaction
  5. Nuclear Energy. The energy absorbed or released during a nuclear reaction (nuclear fission or nuclear fusion)

Kinetic Energy

The energy possed by a body due to its motion, is called its kinetic energy and is given by

KE=½mv²=p²/2m

v = velocity of a body at any time, m= mass of the body and p=linear momentum Thus, kinetic energy of an object increses with its speed. e.g.,
  • When a fast moving cricket ball hits a stationary wicket, the wicket is thrown away.
  • When a raised hammer falls on a nail placed on a piece of wood, it drives the nail into the wood.

Potential Energy

The energy possessed by a body due to change in its position or shape, is callled potential energy. e.g.,
  • Water stored in dam has potential energy due to its position at the height.
  • A stone lying on the roof of the building has potential energy due to its height.
  • A wound spring of a watch has potential energy due to its shape.
The sum of potential energy and kinetic energy of an object, is known as mechanical energy.

Gravitational Potential Energy

When an object is raised through a certain height above the ground, its energy increses. This is because work is done on it against gravity while it is being raised. The energy present in such an object is the gravitational potential energy. The gravitational potential energy of an object at a point above the ground is defined as the work done in raising it from the ground to that point against the gravity.

Gravitational potential energy U = mgh

g= acceleration due to gravity, h= height above the surface, m = mass of the body.

Work-Energy Theorem

According to this theorem, work done by all the forces acting on a body is equal to the change in kinetic energy of the body

Work done = Change in kinetic energy

Law of Conservation of Energy

According to the law of conservation, energy can only be transformed from one form to another. It can neither be created nor be destroyed. e.g., when an object is dropped from the height, its potential energy continuously converts into kinetic energy. When an object is through upwards, its kinetc energy continuously converts into potential energy. The total energy before and after transformation always remains constant.

PE + KE = constant or mgh+1/2mv²=constant

Transformation of Energy

The conversion of energy from one form to other is known as the transformation of energy. The phenomenon of transformation of energy from useful to useless form is known as dissipation of energy.
  • Green plants prepare their own food (chemical energy) using solar energy through the process of photosynthesis.
  • When we throw a ball, the muscular energy which is stored in our body gets converted into kinetic energy of the ball.
  • When an athlete runs, the body’s internal energy is converted into kinetic energy.

Einstein’s Mass-Energy Equivalence

According to Einstein, neither mass nor energy of the universe is conserved but they are interconvertible. The conversion is expressed by the equation E=mc² c=3×108m/s is the speed of light

Work

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Work

Work

When a body is displaced by applying a force on it, then work is said to be done. Example., a girl pulls a trolley and the trolley moves through a distance. In this way, she has exerted a force on the trolley and it is displaced. Hence, work is done. If a body is displaced by a distance (s) on applying a force (F) on it, then the work was done

W= F.s

Thus, work can be defined as ‘work done by a force on an object is equal to the magnitude of the force multiplied by the distance moved in the direction of the force. The SI unit of work is newton-meter (N-m) or joule (J) and its CGS unit is erg. It is a scalar quantity, it has only magnitude and no direction. If F=1 N and s=1 m, then work done by the force will be 1 J.

1 joule = 107 erg

Work done by a Force Acting at an angle

When force F acts on an object in such a direction that it makes an angle θ with the direction of displacements the work done by the force

W=Fscosθ

Value of work will be maximum at θ=0º and minimum at θ=90º

Types of Work

There are three types of work

Positive work

When the force and displacement are in the same direction, then work done will be positive (i.e., work is done by force). e.g., a boy pulls an object towards himself.

Negative work

When the force and displacement are in opposite directionthen work done will be negative (i.e., work is done against force.) e.g., a body is made to slide over a rough horizontal surface, then frictional force acts in the direction opposite tot he direction of displacement, so work done by friction will be negative.

Zero Work

When the force and displacement are in perpendicular direction, then work done is zero e.g.,
  • If a coolie is moving forward carrying load on his head, in this case force is acting vertically downward (weight of load) and displacement is along horizontal direction, so work done is zero.
  • If a body is moving on circle, then after completing one circle work done is zero, because of zero displacement.

Force

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Force
Any action which causes pull or push on a body is called force. Forces are used in our everyday actions like pushing, pulling, lifting stretching, twisting and pressing. Force produces any of the following effects on the body. A force can
  • Move a stationary body
  • Change the state of rest or motion
  • Stop a moving body
  • Change (increase or decrease) the speed of a body.
  • Force Change the shape and size of a body.
  • Change the direction of the motion of a moving body
Force is a vector quantity, its SI unit is Newton and the CGS unit is dyne.

1 newton = 1 kg-ms-2

1 newton = 105 dyne

e.g., a force is used when we kick a football, we lift a box from the floor, we stretch a rubber band, etc.

Fundamental or basic Force in Nature

Gravitational Forces

Every object in this universe attracts each other, this force of attraction is called gravitational force. It is the weakest force among all existing forces and is negligible for all lighter and smaller bodies but becomes significant and considerable in all celestial bodies.

Weak nuclear Forces

These forces were discovered during the study of the phenomenon of β-decay, in radioactivity. These are the forces of interaction between elementary particles of short lifetimes. The weak nuclear forces are 1025 times stronger than gravitational forces.

Electromagnetic Forces

The electromagnetic forces are the forces between charged particles. When the charges are at rest, the forces are called electrostatic forces. The forces between unlike charges are attractive and the forces between like charges are repulsive. These forces are governed by Coulomb’s law. Matter consists of elementary particles like electrons and protons. The electrons and protons are charges. Electromagnetic forces are much stronger than the gravitational force. It dominates all phenomena on atomic and molecular scales.

Strong Nuclear Forces

The forces that bind the neutrons and protons together in a nucleus are called the strong nuclear forces. These forces act between two protons or two neutrons or a proton and a neutron, but only if the particles are very close together. These are strongest forces in nature. These are 1038 times stronger than gravitational forces, 102 times stronger than electrostatic forces and 1013 times stronger than the weak forces.

Types of Force

Balanced Forces

When the net effect produced by a number of forces acting on a body is zero, then the forces are said to be balanced forces. Balanced forces can only bring a change in the shape of the body e.g., If the block is pulled from both the sides with equal forces, the block will not move, such forces are called balanced forces.

Unbalanced Forces

When the net effect produced by a number of forces on a body is non-zero, then the forces are said to be unbalanced forces.
  • An object moves with a uniform velocity when the force acting on the object are balanced and there is no net external force on it.
  • If an unbalanced force is applied to the object, there will be a change either in its speed or in the direction of its motion. Thus, to accelerate the motion of an object, an unbalanced force is required.

CAT Preparation in 60 Days

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CAT Preparation in 60 Days
CAT 2017 will be conducted on 13th October 2017, it’s almost 2 months remaining for the preparation of examination. According to CAT exam pattern, it has a sectional time limit and one cannot choose which section to attempt first and which to attempt second. So how does one prepare for CAT exams in this short span of time: Make a timetable for your CAT and assign more time to the topics in which you feel you are weak. This article will help you to prepare for your CAT exam in a short span of time.

Verbal Ability Section

Read a lot to deal with the Verbal Ability & Logical Reasoning Section of CAT, reading articles on a daily basis not only help improve your vocabulary but also improves your ability to understand and comprehend a lot faster. Read the daily newspaper and weekly magazines, these will also help you to build your General Knowledge.

Grammer

Questions based on grammar are asked in each and every CAT examination, if you feel you are weak in grammar then it’s your turn to go back to basics and face the problems. Grammar is important because it helps you to connect complex and convoluted ideas, it also helps you to read and understand things quickly.
Some best books to improve grammar are:
  • Wren & Martin
  • Better English by Norman Lewis

Data Interpretation and Logical Reasoning

Data Interpretation and Logical Reasoning is always the second section to appear in the CAT examination. Approximately 16 questions are asked from this section.

Get acquainted with caselets

Get familiar with the questions asked in Data Interpretation and Logical Reasoning, the questions asked in this section will be in the form of caselets, and each case consists of 3-4 questions. Data Interpretation (DI) questions are asked in the form of a line, bar graphs, and piecharts etc. Logical Reasoning Questions are mainly based on arrangements, Blood Relations, Family Tree, Venn Diagrams.

Questions on Intensive Calculation

Data Interpretation questions are calculation intensive, use the onscreen calculator provided during the exam. Try to solve questions using calculation trick, as it will save a lot of time.

Quantitative Ability

Quantitative Ability (QA) is the first section of the CAT Question paper. Below are some points which will help candidates to prepare well for the CAT examination. First, go through the syllabus of Quantitative Aptitude for CAT, analyze which section has more weightage and which have less, after that, try to attempt a cat sample paper then evaluate your own weakness and strengths. Pick your old school books to read the topics in which you saw yourself weak and need to work more. Don’t leave out important topics, as it is not possible to read each and every topic, so at least try to read those important topics. Practice lot of CAT sample paper, solving sample paper and the mock test will help you to get acquainted with the types and patterns of questions asked in CAT examination. For a better understanding of each and every topic of CAT examination watch these videos or subscribe to Byju’s YouTube Channel. https://www.youtube.com/watch?v=ZLiPr8xvCe8

Transmission of Heat

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As we know that heat flows from the body at higher temperature to the body at a lower temperature, this flow of heat is known as transfer of heat from one place to another. For that, we have to learn about conduction, convection, and radiation.

Conduction, Convection, and Radiation

Conduction

In solids, heat is transmitted from higher temperature to lower temperature without actual movements of the particles. This mode of transmission of heat is called conduction, e.g., when one of a metallic rod is heated, its other end becomes hot

Convection

The mode of transfer of heat from one part of the medium to another part by the actual movement of the heated particles of the medium is called convection. In liquid and gases, transmission of heat takes place by convection process.

Application of convection

Different applications of convection are as follows i) Formation of Sea Breeze Die to solar heat, the land, and seawater get heated. The ground is heated more quickly than water because water has greater specific heat. The air in contact with the ground is heated due to conduction, so it expands and becomes lighter than the surrounding cooler air. So, the warm air rises resulting in air currents, the cooler air from above moves down fill space. This creates the sea breeze near a large quantity of sea water. In this way, a thermal convection cycle is set up which transfers away from the ground. ii) Formation of Trade Wind The steady surface wind on the earth blowing from north-east towards equator, is called trade wind. Solar heat reaching the equatorial region is higher than that of polar region. So, the air in contact with equator gets heated, becomes lighter and moves towards pole and the cooler air at poles moves towards the equator. So. convection currents set up from equator towards poles. The rotation of earth modifies this current, due to this the air closed to the equator has high speed of 1600 km/h towards east and zero at the poles. iii) Ventilation Convection process is an important part in the ventilation of rooms. When the fire is lighted, the air in the chimney is warmed. It becomes less dense than the air in the room. The warm air is forced out by the cold fresh air which enters the room through the inlet and gaps in the doors and the window. Thus, draughts of air are formed in the room which help to keep the fire supplied with oxygen.

Radiation

The mode of transfer of heat from one body to another without any actual movement the particles involved and without heating, the intervening medium is called radiation. For radiation, there is no need of any medium because it is of electromagnetic nature.    

How far apart to plant tomatoes ?

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Tomatoes plants are transplanted at the plant to plant distance of 45x75cm in indetermined and 45-60×30-40cm in the determined crop.

Tomato is a transplanted crop. Seeds are grown in a raised bed. 25-30 days old seedlings are transplanted. At this age, they got the 10-15cm of height. The tomatoes are transplanted in the evening, on a sunny day. Whole day transplanting is done in a cloudy day. In some of the areas, the tomato is directly sown. Direct sowing has reduced the infestation of root-knot the nematode, bacterial wilt and damping off. The seedlings are transplanted at the side of ridge later earthing up is done to keep the plant in the middle of the ridge.For indeterminate varieties and hybrids, row to row spacing of 60 to 120 cm and plant to plant distance from 45 to 75 cm is adopted. In case of determinate types spacing is 45 to 60 cm x 30 to 40 cm is adopted. What will be your answer please comment below?
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