List of top Science Questions

At the time of short circuit, the current in the circuit
Which of the following correctly describes the magnetic field near a long straight wire?

Write word equations and then balanced equations for the reaction taking place when:
(a) dilute sulphuric acid reacts with zinc granules.
(b) dilute hydrochloric acid reacts with magnesium ribbon.
(c) dilute sulphuric acid reacts with aluminium powder.
(d) dilute hydrochloric acid reacts with iron filings.

Which one of the following types of medicines is used for treating indigestion?

10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the amount HCl solution (the same solution as before) required to neutralise it will be

A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The solution contains

A solution turns red litmus blue, its pH is likely to be

Explain why the bulb would not glow in the arrangement shown in Fig. 9.13.

the bulb would not glow in the arrangement

The process that you saw in Activity 11.7 is used for purification of copper. A thin plate of pure copper and a thick rod of impure copper are used as electrodes. Copper from impure rod is sought to be transfered to the thin copper plate. Which electrode should be attached to the positive terminal of the battery and why?
electroplating

Suppose the two photographs, shown in Fig. had been taken at an interval of 10 seconds. If a distance of 100 metres is shown by 1 cm in these photographs, calculate the speed of the fastest car.

Suppose the two photographs, shown in Fig. had been taken at an interval of 10 seconds

Can the process of rusting be called combustion? Discuss.
Differentiate between regular and diffused reflection. Does diffused reflection mean the failure of the laws of reflection?
Fill in the blanks with suitable words.
  1. Time taken by an object to complete one oscillation is called ___ .
  2. Loudness is determined by the ___ of vibration.
  3. The unit of frequency is ___.
  4. Unwanted sound is called __________ .
  5. Shrillness of a sound is determined by the ___ of vibration.

Given below is a square of letters in which are hidden different words related to respiration in organisms. These words may be present in any direction — upwards, downwards, or along the diagonals. Find the words for your respiratory system. Clues about those words are given below the square.

a square of letters in which are hidden different words related to respiration in organisms

  1. The air tubes of insects
  2. Skeletal structures surrounding chest cavity
  3. Muscular floor of chest cavity
  4. Tiny pores on the surface of leaf
  5. Small openings on the sides of the body of an insect
  6. The respiratory organs of human beings
  7. The openings through which we inhale
  8. An anaerobic organism
  9. An organism with tracheal system
Identify the part which vibrates to produce sound in the following instruments.
  1. Dholak
  2. Sitar
  3. Flute
Mention against each of the following whether regular or diffused reflection will take place when a beam of light strikes. Justify your answer in each case.
1. Polished wooden table
2. Chalk powder
3. Cardboard surface
4. Marble floor with water spread over it
5. Mirror
6. Piece of paper
The bulb does not glow in the setup shown in Fig.11.10. List the possible reasons. Explain your answer.
bulb setup
Describe the different methods of asexual reproduction. Give examples.
Explain in what way noise pollution is harmful to human.
Write a short paragraph on the harmful effects of microorganisms.

Draw:

1) a leaf

2) a taproot and

3) a flower,

you have studied for Table 4.3

Match items in column A with those in column B. 
A B
(i) Kharif crops(a)Food for cattle
(ii)Rabi crops(b)Urea and super phosphate
(iii)Chemical fertilizers(c)Animal excreta, cow dung urine and plant waste
(iv)Organic manure(d)Wheat, gram, pea
  (e)Paddy and maize
Give reasons.
  1. Water is not used to control fires involving electrical equipment.
  2. LPG is a better domestic fuel than wood.
  3. Paper by itself catches fire easily whereas a piece of paper wrapped around an aluminium pipe does not. 
Explain why objects moving in fluids must have special shapes.
Would the bulb glow in the circuit shown in Fig. 9.15?
Would the bulb glow in the circuit