Current Affairs 7th Class

Learning Objectives
  • Introduction
  • Rectilinear propagation of light
  • Reflection of light
  •        - Laws of reflection
  • Image formation
  •      - Plane mirror      - Concave mirror      - Convex mirror
  • Refraction of light
  •      - Concave lens     - Convex lens
  • Dispersion of light
  •       - Rainbow
  • Recombination of the colors of the spectrum
  •      - Newton’s disc   INTRODUCTION Light is a form of energy which creates sensation of vision. Sun is the main source of light. The objects that have their own light are known as luminous objects. Eg. Sun, stars, candle, bulb, etc. The objects that do not have their own light are known as non-luminous objects. Eg. Table, chair, etc. Non luminous objects become visible by light falling on them from some luminous objects.   Do you know? Scientists study the properties and behaviors of light in a branch of physics known as optics   RECTILINEAR PROPAGATION OF LIGHT Light travels in a straight line as long as it is travelling in the same medium. This property of light is known as rectilinear propagation of light. It explains a lot of phenomena associated with light. Light does not require any material medium to propagate. It travels with a very high speed of about \[\text{3}\times \text{1}{{0}^{\text{8}}}\text{m}/\text{s}\] in air or vacuum.   REFLECTION OF LIGHT When light falls on a surface, it bounces off the surface. This is called reflection of light. Reflection always involves two rays - an incoming or "incident" ray and an outgoing or "reflected" ray   Note: we are able to see an object because light from the object can move through space and reach our eyes. Once light reaches our eyes, signals are sent to our brain, and our brain decode the information in order to detect the appearance, location and movement of the objects we are looking at.   Incident ray: This is the ray of light that falls from the source of light on the surface i.e., AO. Reflected ray: This is the ray of light which is reflected from the surface i.e., BO. Normal: An imaginary line perpendicular on reflecting surface is known as normal i.e., NO. Angle of incidence (i): The angle formed between the incident ray and the normal is called the angle of incidence i.e., Z AON. Angle of reflection (r): The angle formed between the reflected ray and the normal is called the angle of reflection i.e., Z BON.   Do you know? Between 18% and 35% of more...

    Learning Objective
  • Introduction
  • Electric circuit and symbols for electrical components
  • Heating effect of electric current
  • - Electric fuse - Electric bulb - CFL
  • Magnetic effect of electric current
  • - Electromagnet - Electric bell
  • Hazards, safety measures and conservation of electricity
  •     INTRODUCTION Electricity is one of the most versatile forms of energy. Electric current is the flow of negatively charged particles called electrons. Depending on whether the electrons remain stationary or move, electricity is classified as static or current electricity. The electric current is generated when electrons are in excess in an electrified object and are free to move towards an object which is less charged. The difference in charge between one object and another object creates potential difference when connected through a conducting wire. Potential difference is the amount of work done per unit charge moved.   Do you know? Both electron and proton have same amount of charge 1.6\[\times \]\[{{10}^{-19}}\] C in magnitude but during positive or negative electrification, it is the electron and not proton that get transferred.   ELECTRIC CIRCUIT AND SYMBOLS FOR ELECTRICAL COMPONENTS Current always flows in a closed loop. This closed loop is called electric circuit. A standard method of drawing an electric circuit is called electric circuit diagram. Symbols of various electric components like cell, wire, battery, and switch are used while sketching electric circuit diagrams. The following table gives the symbols of electrical components. Electrical component
    Connecting wire
    Bulb
    Cell
    Battery
    Key
    Open (OFF) Switch more...
    Learning Objectives
  • What is respiration
  • Respiration in different organisms
  • Cellular respiration
  • Respiration in plants
  • Types of respiration- aerobic and anaerobic respirations
  • Cellular respiration
  •   Do you know? The right lung is slightly larger than the left. The highest recorded sneeze speed is 165 km/hour.   RESPIRATION IN ORGANISMS Respiration The biological process in which food is utilized to produce energy is called respiration. Respiration is necessary for survival of the living beings. A living being cannot survive even for a few seconds, without respiration. During respiration, it is mainly the carbohydrate which is oxidized to produce energy. This can be shown by following equation: Carbohydrate + Oxygen\[\to \]Carbon dioxide + Water + Energy   Site of Respiration Respiration happens inside the cells. As respiration happens inside the cell, it is also called cellular respiration. A cell organelle; called mitochondria; is the site of cellular respiration.   TYPES OF RESPIRATION Aerobic Respiration Aerobic respiration takes place in the presence of oxygen. Carbon dioxide and water are the end products of aerobic respiration. Aerobic respiration happens in most of the organisms. Glucose   \[\xrightarrow{\text{Abresence of oxygen }}\] Carbon dioxide + Water + Energy   Anaerobic Respiration Anaerobic respiration takes place in the absence of oxygen. Anaerobic respiration usually happens in most of the microbes. Alcohol and carbon dioxide are formed at the end of anaerobic respiration. In some cases, lactic acid is formed at the end of anaerobic respiration. Glucose   \[\xrightarrow{\text{Abresence of oxygen }}\] Alcohol + Carbon dioxide + Energy Glucose \[\xrightarrow{\text{Abresence of oxygen }}\]Lactic acid + Energy
    • Anaerobic respiration also happens in our muscle cells. When someone runs or walks too fast, one may feel a throbbing pain in calf muscles. This happens because of deposition of lactic acid; produced by anaerobic respiration. Once the person takes rest for some time, the pain goes away.
    • Yeast respires in the absence of oxygen.
      Do you know?
    • The surface area of lungs is roughly the same size as a tennis court.
    • The capillaries in the lungs would extend 1600 km if placed end to end.
    • The breathing rate is faster in children and women than man.
    • A person at rest usually breathes between 12 and 15 times a minute.
      Glucose is converted into alcohol and carbon dioxide by yeast in the absence of oxygen. Yeast is used in beverage industries to produce beer and wine. During day time, plants utilize oxygen to perform photosynthesis. During the night, plants release carbon more...

    Learning Objectives
  • Importance of water
  • Availability of water
  • Sources of water
  • Depletion of water table
  • Scarcity of water
  • Water management
  • Water conservation
  •   INTRODUCTION About 3000 million years ago the first life form originated in Oceans that covered the Earth. Water is essential for life. We cannot imagine life without water. Not only is water necessary for carrying out the various reactions that occur inside our bodies, it is also required by the industries and laboratories.   Availability of Water on Earth Nearly 71 percent of the earth is covered by water in the form of oceans, seas, lakes, rivers, ice, ground water and moisture in the air. However, most of it is not fit for human consumption. Water that is fit for human consumption is called freshwater. Only 0.006 percent of the water on the earth is actually available for our use.   If a bucketful of water shows the total water on the earth, then a mug of water shows the total freshwater available on the earth. Out of this, a glass of water shows the water which is available as groundwater. About one-fourth spoonful of water shows all the water available in lakes and rivers of the world. In nature, water exists in three forms: solid, liquid and gas.   Forms of Water
    • As a solid, it exists as icecaps at the poles, snow-covered mountains and glaciers.
    • As a liquid, it is in the form of water in oceans, lakes and rivers, and underground water.
    • Its gaseous form is the water vapour in the air around us.
      Water Cycle Water is available in all the three states of matter. Ice is the solid state, water is the liquid state and vapour is the gaseous state; in which water is available. The water on the earth keeps on changing in all the three states in a cycle. This is known as water cycle. The water cycle helps in keeping the amount of water on the earth as constant.   Do you know?
    • Over 90% of the world’s supply of fresh water is located in Antarctica.
    • It takes 200000000 liters of water per second to grow food for the planet.
    • Water is the only mineral found naturally on earth in three forms; liquid, solid and gas.
      Following are the main steps of water cycle in nature: Evaporation: Water from the surface of the earth keeps on more...

     TENSES   The concept of time can be split into:
  • The Present - What you are currently doing.
  •              I eat, I am eating
  • The Past - What you did some time back.
  •              I ate, I was eating
  • The Future - What you will do later.
  •              I will eat, I will be eating In the English language, tenses play an important role in sentence formation. The tense of a verb shows the time of an event or action. There are four types of tenses. Simple, Perfect, Continuous and Present Perfect Continuous and each of these has a present, past and future form.   PRESENT TENSES SIMPLE PRESENT TENSE In Simple Present, the action is simply mentioned and there is nothing being said about its completeness.
    • I eat.
    • I sleep.
    • I play
      PRESENT CONTINUOUS TENSE In Present Continuous, the action is on-going/ still going on and hence continuous.
    • I am eating.
    • I am sleeping.
    • I am playing.
      PRESENT PERFECT TENSE In Present Perfect, the action is complete or has ended and hence termed Perfect.
    • I have eaten.
    • I have slept.
    • I have played.
      PRESENT PERFECT CONTINUOUS TENSE In Present Perfect Continuous, the action has been taking place for some time and is still ongoing.
    • I have been eating.
    • I have been sleeping.
    • I have been playing.
      PAST TENSES SIMPLE PAST TENSE In Simple Past, the action is simply mentioned and understood to have taken place in the past.
    • I ate.
    • I slept.
    • I played.
      PAST CONTINUOUS TENSE In Past Continuous, the action was ongoing till a certain time in the past.
    • I was eating.
    • I was sleeping.
    • I was playing.
      PAST PERFECT TENSE Past Perfect is used to express something that happened before another action in the past.
    • I had eaten.
    • I had slept.
    • I had played.
      PAST PERFECT CONTINUOUS TENSE Past Perfect Continuous is used to express something that started in the past and continued until another time in the past.
    • I had been eating.
    • I had been sleeping.
    • I had been playing.
      FUTURE TENSES SIMPLE FUTURE TENSE Simple Future is used when we plan or make a decision to do something. Nothing is said about the time in the future.
    • I will eat.
    • I will sleep.
    • I will play.
      FUTURE CONTINUOUS TENSE The future continuous tense is used to express action at a particular moment in the future. However, the action will not have finished at the moment.
    • I will be eating at 9 a.m.
    • I will be sleeping when you arrive.
    • I will be playing at 5 p.m.
      FUTURE PERFECT TENSE Future Perfect expresses action that will occur in the future before another action in the future.
    • I will have eaten before 10 a.m.
    • I will have slept before you arrive.
    • I will have played before 6 p.m.
      FUTURE PERFECT CONTINUOUS TENSE Future more...

     COLLOCATIONS   The knowledge of Collocations is very important for proper use of English Language. If we cannot use right collocations, a grammatically correct sentence will stand out awkward. English Collocations fall into the category of Phraseology which means a particular mode of expression, especially one characteristic of a particular speaker or subject area. It is the study of set or fixed expressions, such as idioms, phrasal verbs, and other types of multi-word lexical units (often collectively referred to as phrasemes). In this type of use the component parts of the expression take on a meaning more specific than or otherwise not predictable from the sum of their meanings when used independently. We can say Collocation is the way words are habitually used together to produce a specific meaning. This includes, among others, verbal phrases, verbs compounds, noun compounds, compounds with particles and adjective-noun collocates. In addition to producing specific meaning, collocations or its initiatory parts, increase the predictability of the message and anchor it in the context of communication by signaling to the listener or reader that a specific meaning is about to be proved.   There are several different types of collocations. Collocations can be:
    • Adjective Collocations
    • Adverbial Collocations
    • Verbal Collocations
    • Genitive Collocations
      Example of seven main types of collocations:
  • adverb + adjective
    • Invading that country was an utterly stupid thing to do.
    • We entered a richly decorated
    • Are you fully aware of the implications of your action?
  • adjective + noun
    • The doctor advised him to take regular exercise.
    • The Titanic sank on its maiden voyage.
    • He was writhing on the ground in excruciating pain.
  • noun + noun
    • Let's give Mr Sharma a round of applause.
    • The ceasefire agreement came into effect at 11 am.
    • I'd like to buy two bars of soap, please.
  • noun + verb
    • The lion started to roar when it heard the dog barking.
    • Snow was falling as our plane took off.
    • The bomb went off when he started the car engine.
  • verb + noun The prisoner was hang
    • The prisoner was hanged for committing murder.
    • I always try to do my homework in the morning, after making my bed.
    • He has been asked to give a presentation about his work.
  • verb + expression with prep
    • We had to return home because we had run out of money.
    • At first her eyes filled with horror, and then she burst into tears.
    • Their behaviour was enough to drive anybody to crime.
  • verb + adverb
    • She placed her keys gently on the table and sat down.
    • Sweety whispered softly in Raj’s ear.
    • I vaguely remember that it was growing dark when we left.
      SOME EXAMPLES OF COMMON COLLOCATIONS VERB COLLOCATIONS more...
     COMPREHENSION (PROSE & POETRY)   READING COMPREHENSION Being an area that tests a candidate's understanding of the language, comprehension consists of questions based on given text (a passage, one or more paragraphs). Questions may even be based on certain real-life situations to test how good a candidate is at fact-finding, sifting through information, interpreting text, concluding from given information and discerning between stated and implied meanings of the given information. Understanding of vocabulary, rhetorical tools, hunting for the required information while keeping the holistic picture in mind, etc., are essential comprehension skills at play in this area. Poetry comprehension requires deeper understanding of the poetic devices and literary expressions. You have to be acquainted with these areas practising small passages first.   TIPS FOR POETRY COMPREHENSION
  • Realize complete understanding, as with any poem, will not come after one reading.
  • Use clues from the poem's title to identify the topic. Often the topic will not be stated explicitly in the poem.
  • Read through the poem once to get a general idea of what the poem's about. Don't try to figure it out the first time through.
  • Pay attention to punctuation and the physical structure of the poem.
  • Consider, first, the literal meaning of the poem; that is, what is the concrete object or idea being discussed. Once that is identified, concern yourself with analysis and symbolic meaning.
  • Analyze imagery and figurative language. What is the author's purpose?
  • Identify parts of the poem that confuse you. Can you use the poem's context to interpret confusing parts?
  • Consider multiple ways of interpreting the poem. There may be more than one correct interpretation.
  • Read the poem aloud. Sound devices are often clues to the poem's meaning.
  • The role of vocabulary development and instruction play an important role in helping students to understand the complex cognitive process of reading.
  • The reader must be actively involved with the text by intentionally thinking about what he or she is reading.
  • To comprehend means 'to understand and grasp'. A comprehension exercise is, therefore, meant to test a candidate's ability to understand and retain the contents of a given passage.   Trend of Questions: In this type of questions, generally a long passage consisting of certain paragraphs is given, followed by 10-15 questions based on it. The questions may be based on: (i) Theme of the passage (ii) Choosing the correct or wrong statement on the basis of the given passage (iii) View of the author regarding the main point discussed in the passage (iv) Synonyms or Antonyms of some selected words in the passage   The technique of Solving:
  • Read the passage carefully once and detect its theme.
  • Note what the questions are about.
  • Answer the questions.
  • "In Questions on Synonyms & Antonyms, what is to be remembered is that the answer is to be given according to the sense in which the word has been used in the passage, not just on the basis of its literal meaning.   Example: Read the following passage and answer the more...

     ADVERTISEMENTS GRAPHS/IMAGES   DEFINITION Advertising brings a product (or service) to the attention of potential and current customers. Advertising is focused on one particular product or service. Thus, an advertising plan for one product might be very different from that for another product. Advertising is typically done with signs, brochures, commercials, direct mailings or e-mail messages, personal contact, etc. Advertising is the activity of drawing public attention to a product or service in order to encourage people to buy it.   CREATING AN ADVERTISEMENT It seems very difficult to craft a perfect advertisement to entice potential consumers or influence public opinion. But the right way to make a good advertisement is to keep simple. An ad sums up everything that is smart, innovative, and distinguished about your brand, and is almost indispensable in today's economic marketplace.   WRITING THE ADVERTISEMENT Advertisers create ads for an intended audience. They have a purpose behind designing an advertisement and publishing it in a particular way. Advertising affects people in different ways. People today are exposed to a large amount of advertising. A catchy, snappy tagline is the sole of an advertisement. Keeping short and sweet within six or seven words might serve the purpose. Loud sounding advertisements appeal less to our senses. The immediate purpose of advertisement is to garb the consumer's attention and convince him or her that your product is different from others.   AVOID THE SAME OLD CLICHES Being memorable is the key to good advertisement. Avoid terms like-new and improved, guaranteed, or free gift-is there any other kind?
    • Startle the reader to pay attention because it is especially useful if you have a lot to say. For example long announcement wouldn't turn many heads if it weren't for the unusual, confrontational tagline; if the reader wants to get the joke, she or he has to read more.
    • Know how to walk the line between controversial and entertaining. Pushing the limits of good taste to help your ad grab attention is common practice, but don't go too far — you want your product to be recognised on its own merits, not because it was tied to a tasteless advertisement.
    • Use a persuasive technique. There are tried and true methods that advertisers rely on to make their ads stick.
    These include:
    • Common sense: Challenging the consumer to think of a good reason why not to purchase a your product or service.
    • Humour: Making the consumer laugh, make you more likeable and memorable. Your advertised lines should be short.
    • Repetition: Repeating key elements will bring good results.
    • Exigency: Convincing the consumer that time is of the essence. Limited-time only offers, fire sales, and the likes are the commonest ways to do this, but again, avoid meaningless phrases that will slip under your customers' radar.
    • Know the customer. Even the cleverest ad won't work if it doesn't appeal to the target audience. Are you looking for a certain age group? Do you want people with a more...

     DRAWING CONCLUSIONS AND INFERENCES   DEFINITION When we read a text, the author does not always tell us everything. The author may leave out details on purpose. He may also depend on the reader’s general knowledge to fill in the blanks. Inference: an idea that is suggested by the facts or details in a passage. Conclusion: a decision about what may happen or about the result an event may have Making an inference and drawing a conclusion are very similar skills. Ach requires the reader to fill in the blanks left out by the author. An author may not include information for several reasons: they may think you already know it, it may not seem important to them, or they may want you to find the result.   How to make an inference or draw a conclusion
    • Observe all the facts, arguments, and information given by the author
    • Consider what you already know from you own experience
    • When faced with multiple choice answers, determine whether each is true or false based on the information in the passage
    Example The woman waited nervously in the line. When the counter was empty, she carefully unloaded her items from her cart. Lines creased her forehead as if to show the calculations ringing up in her head. Finally, the cashier began ringing up the items as the woman clutched her purse. Inference/ conclusion: The woman may not have enough money to cover the cost of her groceries
    • Think about the fact of the passage and what may result from them
    • Think about causes and effects
    The writer may only provide a list of effects, so you have to figure out the cause. The child stood on the sidewalk clenching her ice cream cone. Beads of sweat collected on her little nose as she furiously licked at the ice cream dripping down her hand. Inference/ conclusion: IT must be hot day because her ice cream is melting, and she is sweating.
    • Try saying “If…. then"
    If the girl is sweating, then it may be warm outside.   Remember
    • Most writing suggests more than it says
    • By making inference, you get more from the story.
    • Conclusions may be missing from the things you read, so you have to draw your own
      PRACTICE ACTIVITIES Sujata almost wished that she hadn't listened to the radio. She went to the closet and grabbed her umbrella. She would feel silly carrying it to the bus stop on such a sunny morning. 1. What probably happened? (a) Sujata realised that she had an unnatural fear of falling radio parts. (b) Sujata had promised herself to do something silly that morning. (c) Sujata had heard a weather forecast that predicted rain. (d) Sujata planned to trade her umbrella for a bus ride. "Larry, as your boss, I must say that it's been very interesting working with you," Miss Sharma said. "However, it seems that our more...

     PARA JUMBLES   DEFINITION The section deals with the problems of Jumbled paragraph and sentences and sentence and phrase arrangement of the given phrases or sentences. The student has to choose a logical sequence to make a meaningful sentence or paragraph. This form of exercise tests the student's ability to (a) Figure out the logic of the events (b) Sequence of different parts of a combination according to correct grammatical usage. In either sentence or paragraph structuring, the student has to check which part follows the other according to the logical theme of the sentence/paragraph. (a) Phrase arrangement or Jumbled Sentence. (b) Sentence arrangement or Jumbled Paragraph. In a jumbled sentence, a sentence is broken into four parts and the student has to figure out, the right sequence to form a logical, sensible sentence. Consider the following example.   Example I. P: by her indulgent parents Q: the child was so spoiled R: when she did not receive all of their attention S: that she pouted and became sullen (a) RQPS                                 (b) QRPS (c) QPSR                                 (d) QSPR In this question, a single sentence has been broken into four different parts and the student has to find out the logical sequence of the sentence. In order to do that, consider the following. Strategy I: Decide on the opening phrase, first. The opening part of the sentence will usually contain the subject of the sentence. So locate the subject and select that part as the first in sequence. Now, select all options in the answer that begin with the part you have chosen as the first. In example 1, the subject is the child and the opening part will be Q, thus, we can eliminate option (a). Now, since the subject is passive, the verb form will be followed by 'by' and the doer. So, find the second part beginning with by and containing the doer of the action which in this case is P. Thus, we can reach the right answer, option (c). Strategy II: If the Subject is passive, mostly, the following part will begin with 'by and contain the doer of the action in the sentence.   Example II. Unsurpassed power (P)/modern society (Q)/in (R)/ women enjoy (S) (a) RQPS                                  (b) SRPQ (c) SPRQ                                (d) PSRQ The subject of the sentence is women so the opening part would be S. Thus, we have to choose between options (b) and (c). The subject in this sentence is active. So, we must find the object which will be the next Part. In the given question, the object is unsurpassed power. Thus, the answer is (c). Strategy III: When the subject is active, follow the sequence- SUBJECT - VERB - OBJECT Strategy IV: Preposition is never the last part. If a preposition is given as one of the parts match it with other parts to find out what will follow the preposition. In Example III 'in' could only be followed by Modem society, so more...


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