Science class 10 PYQ, Study notes of Physics

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REPEATED PREVIOUS YEAR QUESTIONS

CLASS 10th - SCIENCE

1. (a) What is the colour of ferrous sulphate crystals? How does

this colour change after heating?

(b) Name the products formed on strongly heating ferrous

sulphate crystals. What type of chemical reaction occurs in this

change

2. A student suffering from myopia is not able to see distinctly

the objects placed beyond 5 m. List two possible reasons due to

which this defect of vision may have arisen. With the help of ray

diagrams, explain

2. A student suffering from myopia is not able to see distinctly the objects placed beyond

5 m. List two possible reasons due to which this defect of vision may have arisen. With

the help of ray diagrams, explain

ANSWER: Two possible reason due to which the defect of vision may have arisen

are:

(1) increase in curvature of the lens.

(2) increase in length of the eyeball.

3. (a) Define excretion.

(b) Name the basic filtration unit present in the kidney.

(c) Draw excretory system in human beings and label the following organs of excretory

system which perform following functions: (i) form urine. (ii) is a long tube which collects

urine from kidney. iii) store urine until it is passed out.

ANSWER: (a) The biological process involved in the removal of these harmful metabolic wastes from the body is called excretion. (b) The basic filtration unit in the kidney is known as Nephron. (c) i. kidney form urine. ii. The ureter is the long tube which collects the urine from Kidney. iii. The urinary bladder is a structure which stores the urine until it is passed.

(c)

4. Both soap and detergent are some type of salts. What is the

difference between them? Describe in brief the cleansing action

of soap. Why do soaps not form lather in hard water? List two

problems that arise due to the use of detergents instead of

soaps.

5. (i) Name and state the rule to determine the direction of

force experienced by a current carrying straight conductor

placed in a uniform magnetic field which is perpendicular to it.

(ii) An alpha particle while passing through a magnetic field

gets projected towards north. In which direction will an

electron project when it passes through the same magnetic

field?

5. (i) Name and state the rule to determine the direction of force experienced by a current

carrying straight conductor placed in a uniform magnetic field which is perpendicular to it.

(ii) An alpha particle while passing through a magnetic field gets projected towards north. In

which direction will an electron project when it passes through the same magnetic field?

ANSWER: (i) Fleming's left hand rule. According to this rule : Stretch the thumb, fore finger and middle finger of your left hand such that they are mutually perpendicular. If the forefinger points in the direction of magnetic field and the middle finger in the direction of current, then the thumb will point in the direction of motion or force acting on conductor. (ii) As the direction of the force on a negatively charged electron will be opposite to that of a positively charged alpha particle hence, an electron will experience a force that pushes it towards the south when it passes through the same magnetic field as that of alpha particle.

6. (a) What is ozone? How is it formed in the upper layers of the Earth's atmosphere? How

does ozone affect our ecosystem?

(b) “We do not clean a pond in the same manner as we do in an aquarium." Give reason to

justify this statement.

ANSWER: (a) Ozone is a molecule formed by three atoms of oxygen.

UV radiations split some molecular oxygen (O2) into free oxygen atoms (O + O).

These atoms then combine with molecular oxygen to form ozone.

Ozone layer shields the surface of the earth from damaging UV radiation of the

sun. / Depletion of ozone layer causes harmful effects on the organism.

(b)A pond is a natural ecosystem. It has decomposers whereas an aquarium is

an artificial ecosystem and does not contain decomposers. Therefore it needs

regular cleaning for proper functioning.

7. Write the name and the structural formula of the compound

formed when ethanol is heated at 443K with excess of conc.

H2SO4. State the role of conc. H2SO4 in this reaction. Write

chemical equation for the reaction.

8. (a) If the image formed by a mirror for all positions of the

object placed in front of it is always diminished, erect and

virtual, state the type of the mirror and also draw a ray diagram

to justify your answer. Write one use such mirrors are put to

and why.

(b) Define the radius of curvature of spherical mirrors. Find the

nature and focal length of a spherical mirror whose radius of

curvature is + 24 cm.

8. (a) If the image formed by a mirror for all positions of the object placed in front of it is

always diminished, erect and virtual, state the type of the mirror and also draw a ray diagram

to justify your answer. Write one use such mirrors are put to and why.

(b) Define the radius of curvature of spherical mirrors. Find the nature and focal length of a

spherical mirror whose radius of curvature is + 24 cm.

ANSWER:

(a) If the image formed by a mirror for all positions of the object placed in front of it is always diminished, erect and virtual, then the type of the mirror is Convex. Such mirrors are used as rear view mirrors in automobiles, as this type of mirror gives erect, and a wider field of view of objects coming behind the automobile.

9. Which one of the two multicellular organisms Spirogyra and

Planaria reproduces by regeneration and why? Give an

example of any other organism which can also reproduce by

the same process.

9. Which one of the two multicellular organisms Spirogyra and

Planaria reproduces by regeneration and why? Give an example of

any other organism which can also reproduce by the same process.

ANSWER: Planarians can regenerate new

heads, tails, sides, or entire organisms from

small body fragments in a process taking days

to weeks. For example, a planarian split

lengthwise or crosswise will regenerate into

two separate individuals. Whereas in Spirogyra

asexual reproduction takes place by

fragmentation.