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29 July 2014

IX Bio. Why do we fall ill? NCERT solved questions

Q. What is an antibiotic? Give its one example 

Ans: Antibiotic is a chemical substance that kill bacteria, secreted by microorganismswhich can kill the pathogens Example – Penicillin 

Q. (i) Which disease is more harmful : Acute or Chronic disease ? Why? 
(ii) Why are we advised to take bland and nourishing food when we are sick? 

Ans: (i) Chronic disease 

Because chronic diseases have drastic long term effects on people’s health as compared to acute disease


(ii) (a) Such food does not contain oil or fat and spices so it is digested easily

(b) It provides sufficient energy for recovery after the disease

(c) It provides adequate amount of nutrients required for regeneration of cells and tissues.

Q. (i) How atmospheric inert nitrogen gas is converted into usable nitrogenous form for the various life forms? (ii) Draw a labelled diagram to show nitrogen cycle in nature
Ans: (i) (i) By the help of free living nitrogen fixing bacteria or nitrogen fixing bacteria found in roots of legumes.

(b) Physical process : During lighting, the high temperatures and pressures created in the air convert nitrogen into oxides of nitrogen. These oxides dissolve in water to give nitric and nitrous acids and fall on land along with rain.

Q. (i) What are the consequences of Global warming (ii) Why is water essential to life?
Ans: (i) Rise in temperature (ii) Melting of glacier

(ii) (a) All life processes require water. (b) Water is needed for transportation of substances from one part of body to other in dissolved farm.

Q. Name the causal organism of AIDS. Why a person suffering from AIDS cannot fight even very minor infections ?
Ans: HIV (virus)

The virus goes to the immune system and damages its function. So the body can no longer fight off even minor infections.

Q. Write the symptoms when following organs are targeted by microbes. (a) Lungs (b) Liver (c) Brain.
Ans: Lungs – cough , breathlessness. Liver – Jaundice Brain – Headache, vomiting, fits

Q. What is immunization? List two diseases against which vaccines are available.
Ans: Immunization is the process in which a person's immune system is enhanced by giving inactive form of the disease causing agent ( immunogen). This agent develops the human immune system to fight against that agent and if attacked again by the same agent the immune systems give a more stronger response and eliminate the disease.

Two diseases for which vaccines are available are Polio and Diphtheria.

Q. Write the full form of AIDS. List four modes of transmission of virus of this disease.
Ans: Aquired Immuno Deficiency Syndrome

Modes of transmission of virus of this disease

a) Through sexual contact

b) Through blood trsnsfusion From mother to child

c) Through infected needled or syringes

Q. Health workers are exposed to more sick people than others in the community. Writeany four preventive measures they take to avoid sickness.
Ans: Preventive measures:

(i) Hand washing after any direct contact with patients

(ii) Wearing gloves while treating or examining the patient.

(iii) Proper disposal or sterilizing the instruments.

(iv) Immunisation.

Q. Same drug does not work against the microbes belonging to different groups. Why? State the mechanism of antibiotics in killing bacteria.
Ans: Every micro organism has its own biochemical cycle. So one type of antibiotic can stop or block biochemical cycle of one type of micro organism only but not all type of micro organisms. Antibiotic destroy the cell wall during the asexual reproduction cycle hence the bacteria can be easily killed.

Q. “Water is essential for living organisms”. State two reasons to justify this statement.
Ans: Water is needed by organisms to maintain their body temperature. Water is needed by organisms to perform many biochemical reactions.

Q. List the names of three diseases caused by virus stating their mode of communication in each case.
Ans: (1) Influenza (2) Hepatitis (3) AIDS

Mode of communication

(1) Blood transfusion (2) Unprotected sexual contact (3) Use of contaminated needles syringes etc. (4) From mother ‘to foetus thmyh’ placenta

Q. List four preventive measures against communicable diseases.
Ans: 1. Health education 2. Isolation 3. Proper sanitation 4. Sterilization of articles used by patients 5. Vaccination 6. Provision of safe water supply

Q. A person has lost his power to fight infections. Name the disease the person is suffering from. State the pathogen and modes of transmission of this disease.
Ans: Suffering from AIDS Name of pathogen is a virus known as HIV. Mode of transmission of HIV is :

1. Intimate sextual contact

2. Blood transfusions

3. Contaminated needles, syringes or razors (Any 2 points)

Check it out

Class IX Biology Chapter - Why do we fall ill?   NCERT Solutions
CCE Test Paper Biology     Chapter:  Why do we fall ill?   Solved Questions
NCERT Solved Board Questions 9th Science: Ch-13.  Why do we fall ill?
Class IX  Biology Ch-13.Why do we fall ill-Chapter Notes

21 July 2014

CLASS VIII physics Chapter Sound Solve CBSE Exam Assignments

Q.1 How does a sound making object differ from one that is silent?
Answer: Sound making object can vibrate easily.                      
Q.2 How does sound from a sound producing body travel through air to reach our ears?
Answer: Sound from a sound producing body travel through air to reach our ears by making regular compression and rarefaction.
Q.3  Why are the voices of men, Women and children different?
Answer: The voices of men, women and children differ from each other due to the following factors:
1) The pitch is one of the most essential factors to determine the voice of the individual. For example, men have lower-pitched voices while women have higher-pitched voices.
2) Second factor which brings in the difference in the voices is the length and the thickness of vocal cords.
Q.4  Why a sound cannot be heard on the moon?
Answer: A sound cannot be heard on the moon due to absence of medium air
Q.5  How do astronauts talk to one another on the surface of moon and Why?
Answer:  Astronauts communicate with the help of radio waves on moon because these waves do not need a medium to travel
Q.6  If you want to hear a train approaching from far away, why is it more convenient to put the ear to the track?
Answer: This is because sound can travel through railway track (solid ) faster than through air.
Q.7  State one observation from everyday life which shows that sound travels much more slowly than light?
Answer: We hear thunder after lightining.
Q.8  What is the scientific name for the following? The number of vibrations made per second.
Answer: Frequency
Q.9   Why do we not hear the screams of a bat?
Ans: This is because the screams are ultra sonic(above 20,000 hertz) which human ear cannot hear.
Q.10  Which of the following frequency of sound can be heard by a dog but not by a man?                                                                     (a) 50,000 hertz (b)   15,000 hertz
Answer:  A sound of frequency 50,000 hertz can be heard by a dog but not by a man
Q.11 Explain how, noise pollution {or excessive loud noise} is harmful to human beings.
Answer: Noise pollution can lead to a number of health-related problems. Some of them are as follows:
(i) Hearing loss  (ii) inability to sleep         (iii) Hypertension (iv) Severe headache (v) Stress
Q.12  State the various measures which can be taken to control {or reduce} noise pollution in our surroundings.
Answer: Noise pollution can be reduced by using silencers in vehicles, industrial machines, and home appliances reducing use of vehicle horns, running TV, radio and music systems at low volumes. Planting of trees along roads and buildings also help to reduce noise pollution.
Q.13 Give two causes of noise pollution from the homes.
Answer: . In the home noise pollution is caused by television radio and  music systems at high volume, some kitchen appliances, desert coolers, air conditioners etc.
Q.14   Sound of different pitch can be produced using a flute. Explain, how?  
Answer: If we blow a flute, the air column vibrates and produces sound. Flute contains small air columns, when air is bowed through the mouth piece the air columns start vibrating which produces sound.
Q.15.How does Sound produced by humans?
Answer:     In humans sound is produced by the vioce box or larynx. It is the upper part of the wind pipe. Two vocal cords are stretched across the voice box leaving a narrow slit. When the lungs force air through the slit, it vibrates and produces sound.
Q. 16. How Jal Tarang produces sound?
Answer: In Jal-tarang musical instrument the cup containing minimum water produces the sound of lowest frequency or lowest pitch. As the amount of water in the cup goes on increasing, the frequency (or the pitch) of the sound produced also goes on increasing.
Q. 17. If 125 oscillations are produced in 5 seconds, what is the frequency in hertz?
Answer: in 5 seconds 125 oscillations are produced
So, in 51 seconds 125/5 = 25 oscillations are produced
Hence, the frequency = 25Hz
Q. 18. What is the frequency of a vibrating body whose time-period is 0.05 second?              
Answer: f = 1/t = 1/0.05 = 100/5 = 20HZ
Q. 18. State true or false
(i) Sound can be produced by beating an object irrespective of whether there are vibrations or not.
(ii)The sound of a tabla normally has a lower pitch than the sound of a violin.
(ii)A short flute will produce sound of lower pitch than a long flute.
Answer: (i) –False [Sound is produced from a vibrating object.]
(ii) -True [The sound of a tabla normally has a lower pitch than the sound of a violin.]
(iii) –True[A short flute will produce sound of lower pitch than a long flute.]
Q.19. Give reasons Why Trees planted along the roads reduce noise?
Answer: Trees are planted along the roads and around buildings so that it could cut off sound vibrations produced from vehicles speakers etc. by absorbing them, hence leading in prevention of Noise pollution.
Q.20. what are transverse and longitudinal waves?
Answer: Longitudinal waves: A wave in which the particles of the medium vibrate back and forth in the same direction in which the wave is moving is called longitudinal wave. Example: sound waves.
Transverse waves: A wave in which the particles of the medium vibrate at right angles to the direction, in which the wave is moving, is called transverse wave. Example: Light waves.
Assignments for practice 

1. How sound is produced?

2. What do you understand by a ‘wave’?

3. Write three differences between sound and light waves.

4. What do you understand by “sound energy cannot be produced”?

5. What is the name of the wave that can travel through vacuum?

6. Explain by some experiment that sound waves require medium for their propagation.

7. How sound waves travel through some medium?

8. Why sound waves do not propagate through vacuum?

9. What are the transverse waves? Give two examples.

10. What are longitudinal waves? Give two examples.

11. Give two points of difference between longitudinal and transverse waves.

12. How will you prove that the sound waves exhibit longitudinal behaviour?

13. What are rarefaction and compression in case of sound waves?

14. Distinguish between crests and troughs.

15. Write the SI unit of velocity of a wave.

16. What are the factors that describe the sound wave and define them?

17 Why is a thundering sound heard later than lightening?

18. Sound travels with different speeds in different media. Comment.

19. How far is a compression and its nearest rarefaction in a longitudinal wave?

20. Define sound ranging.

21. What is the frequency range of sound for human beings?

22. What are the ultrasonic and supersonic waves?

23. What type of waves are produced by animals like bats and dolphins?

24. Explain two applications of ultra sound waves?

25. Explain how ultrasound waves are used to detect a flaw in an object?

26. Which sound wave is used in ECG (echocardiography)?

27. Give the full form of SONAR.

28. Name the technique used to measure the depth of a sea.

29. How will you determine the depth of a sea using SONAR?

30. How do the bats fly in dark?

31. How RADAR is different from SONAR?

32. Explain the function of ear by explaining its each part.



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03 July 2014

X Science Questions From CBSE Examination Papers Ch: Magnetic Effect of currents

1. Q. What is solenoid? Draw the pattern 0f magnetic field line of a solenoid through which steady current flows
2 Marks
2. Q. What are permanent magnet and electromagnet? Give two use of each.
2 Marks
3. Q. Differentiate short circuit and over loading?
2 Marks
4. Q. Draw the pattern of magnetic field lines of produce by current carrying circular loop
2 Marks
5. Q. What is role of fuse in domestic circuit? Why we use the fuse of defined rating not be replaced by one with large rating?
2 Marks
6. Q. How will deflection of compass get affected if current in straight wire is increased? support your answer with reason?                                        
2 Marks
7. Q. No two field line intersect each other . Explain?                          
2 Marks
8. Q. What is the direction of thumb indicates in right hand thumb rule? In what way this rule is different from Fleming’s left hand rule?  
2 Marks
9. Q. Why does a current carrying conductor kept in a magnetic field experience force? On what factor does the direction of this force depend? Name and state the rule used determination of direction of current?
2 Marks
10. Q. Two circular coil A and B placed closed to each other If the current in coil A is changed, will some current be induced in the coil B? Give reason?
2 Marks
11. Q. What do you mean by term magnetic field line? List any two properties?
2 Marks
12. Q. Give an activity to show magnetic field produce by current carrying circular loop?
2 Marks
13. Q. What precautions should be taken to avoid the overloading of domestic circuit? 
2 Marks
14. Q. Why do we connect earth wire in house give two reason?
2 Marks
15.Q. Write four properties of magnetic field lines?
2 Marks

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