STD-6, CHAPTER-14: FABRIC FROM FIBRE, EXERCISE QUESTION ANSWERS

 A.     FILL IN THE BLANKS.

1.      Cotton plants grow well in _____ soil.

Ans: black

2.      Cotton is obtained from the _____ of the cotton plant, called _____.

Ans: fruit, bolls

3.      The body coat of sheep is called the ______.

Ans: fleece

4.      Wool is obtained from the body coat of animals like the ____, _____ or _____.

Ans: sheep, goat, camel

5.      Jute is obtained from the _____ of jute plant.

Ans: bark (stem)

B.      MATCH THE FOLLOWING:

 

1.      Fibres into threads                                       a. dyeing

2.      Thread into fabric                                         b. finishing

3.      Colouring the fabric                                     c. spinning

4.      Making patterns on fabric                          d.  weaving

5.      Making fabric smooth and shiny               e. printing

      Ans:

1.      Fibres into threads                                       c. spinning

2.      Thread into fabric                                        d. weaving

3.      Colouring the fabric                                     a. dyeing

4.      Making patterns on fabric                          e. printing

5.      Making fabric smooth and shiny               b. finishing

 

C.      TICK THE CORRECT OPTION.

 

1.      Which one of these is not a man-made fibre?

(a)   nylon        (b) tereyline           (c) linen        (d) rayon

      Ans: linen

2.      From the following, the only incorrectly matched ‘pair’ is-

(a)   Silk-mulberry              (b) jute-stem         

(c) cotton-seeds                (d) coir-outer covering of coconut

      Ans: cotton-seeds

3.      The process, of pulling and twisting of strands to make a fibre, is known as-

(a)   printing

(b)   spinning

(c)    weaving

(d)   dyeing

       Ans: spinning

4.      ‘Weaving’ is done by using machines called-

(a)   taklis                                    (b)  charkhas

(c)    looms                                   (d)  needles

      Ans: looms

5.      Jute and cotton plants grow well, respectively, in-

(a)   Alluvial, and black, soils

(b)   Black, and alluvial, soils

(c)    Black, and ordinary, soils

(d)   Ordinary, and alluvial, soils

      Ans: alluvial, and black, soils

D.     ANSWER THE FOLLOWING QUESTIONS IN BRIEF.

 

1.      How are clothes important for us?

Ans: Clothes protect ourselves from heat, cold, rain and germs.

2.      Define the term ‘natural fibres’.

Ans: Fibres, which are obtained from natural sources, that is, plants and animals, are called natural fibres.

3.      Give two examples of plant fibres.

Ans: Cotton and jute are two examples of plant fibres.

4.      Name the kind of soil that is suitable for growing jute plants.

Ans: Alluvial soil is suitable for growing jute plants.

5.      Where is coir obtained from?

Ans: Coir is obtained from the outer covering of coconut.

E.      ANSWER THE FOLLOWING QUESTIONS.

 

1.      State the conditions that help in growth of cotton plant.

Ans: i) Black soil is suitable for the growth of cotton plant.

ii) Warm and humid climates, having temperature of over 16⁰ C, provide the most suitable conditions for the growth of the cotton plant.

2.      Why do we need to use ‘fresh soil’ for cultivating jute plant every year? State any three uses of jute.

Ans: i) Jute plant uses up the fertility of the soil to a large extent. Fresh soil is, therefore, needed every year for growing jute plants.

ii) Jute is used for making ropes, gunny bags and mats.

3.      Give the difference between ‘spinning’ and ‘weaving’.

Ans:

Spinning	Weaving
The process of twisting the raw fibres together to make yarn, is called spinning.	The process of making clothes from yarn is called weaving.
Charkha is used for spinning.	Loom is used for weaving.

 

4.      Write, in correct sequence, the names of the steps involved in the production of cloth.

Ans: The steps involved in the production of cloth are,

i) collecting fibres from different sources

ii) spinning

iii) weaving

iv) dyeing

v) printing

vi) finishing

vii) tailoring

5.      Differentiate between natural and synthetic fibres. State any three advantages of synthetic fibres over natural fibres.

Ans:

NATURAL FIBRES	SYNTHETIC FIBRES
Fibres, obtained from natural sources, like plants and animals, are called natural fibres.	Fibres, made from chemicals, that are prepared in factories are called synthetic fibres.
Cotton, Jute, Linen are some examples of natural fibres.	Nylon, terylene and rayon are some examples of synthetic fibres.

 

Three advantages of Synthetic fibres over natural fibres

They are stronger, wrinkle-free, do not shrink and are not spoiled by moths.

STD-4, CHAPTER-10: WATER POLLUTION, EXERCISE QUESTION ANSWERS

 

D.     ANSWER THE FOLLOWING QUESTIONS IN BRIEF.

 

1.      Name any two materials which can make rain water impure.

Ans: dust and smoke can make rain water impure.

2.      Name any two human activities which can cause water pollution.

Ans: Throwing wastes and bathing cattle in water bodies can cause water pollution.     

3.      Which two pollutants are often dumped by the factories into the rivers?

Ans: Waste materials and harmful chemicals are often dumped by the factories into the rivers.

4.      Name any two diseases that may be caused by drinking polluted water.

Ans: Two diseases that may be caused by drinking polluted water are typhoid and cholera.

5.      Write the names of two types of materials, used by farmers, to increase the production of crops.

Ans: The two types of materials, used by farmers, to increase the production of crops are, pesticides and chemical fertilisers.

 

E.      ANSWER THE FOLLOWING QUESTIONS.

 

1.      How do wastes, from factories and fields, affect the aquatic animals?

Ans: Wastes, from factories and fields, increase the growth of micro-organisms in water. This reduces the supply of oxygen for the aquatic animals.

2.      How can polluted water affect the crops?

Ans: When polluted water is used for irrigation, the fertility of the soil gets reduced and crops can get damaged.

3.      Why are oil spills harmful for marine life?

Ans:  Oil spills form a cover on the surface of water. This cuts off the oxygen supply to the animals living under water.

4.      State any four effects of water pollution.

Ans: (i)  Water pollution leads to the death of marine animals.

(ii) It decreases the fertility of the soil.

(iii) It causes diseases like jaundice, cholera etc.

(iv) It reduces the oxygen supply to the aquatic plants and animals.

5.      State four ways of reducing water pollution.

Ans: Four ways to reduce water pollution are,

(i) wastes from factories and power houses should not be allowed to flow into rivers directly.

(ii) People should not wash clothes, or use soaps if they bathe, in rivers.

(iii) Water, from drains or sewage, should not be allowed to enter into wells or rivers.

(iv) The use of chemical fertilisers should be minimised.

STD-6, CHAPTER-13: MAGNETS, EXERCISE QUESTION ANSWERS

 

A.     FILL IN THE BLANKS.

1.      The materials which do not get attracted towards a magnet are called _______.

Ans: non-magnetic substances

2.      The bar magnet is an example of a ______ magnet.

Ans: artificial

3.      Even the smallest piece of a bar magnet has two _____.

Ans: poles

4.      Earth has its magnetic _______ towards its geographical south pole.

Ans: north pole

5.      Magnets have been used for ______ purposes.

Ans: navigation

B.      WRITE TRUE OR FALSE FOR THE FOLLOWING STATEMENTS.

 

1.      Naturally occurring magnets are called loadstones.                                             True

2.      An aluminium foil would get attracted by a magnet.                                           False

3.      Bar magnets have a ‘north seeking’ pole as well as a ‘south seeking’ pole.    True

4.      Two magnetic poles, of the same kind, attract each other.                                False

5.      When two magnets are moved farther apart from each other, the forces, that attract or repel them, tend to become stronger.                                                                                            False

C.      TICK THE CORRECT OPTION.

 

1.      The magnetic material, that was discovered first of all, is-

(a)   iron        (b) steel         (c) loadstone       (d) cobalt

      Ans: loadstone

2.      A magnet can attract-

(a)    a glass object             (b) a flower         (c)  a book         (d) an iron nail

      Ans: an iron nail

3.      A material, that is often used to make a temporary magnet, is-  

(a)   steel       (b)  alnico      (c)   ticanol     (d) soft iron

       Ans: soft iron

4.      When we suspend a bar magnet from a thread, it comes to rest along the–

(a)    North-west direction                                  (b)  east-west direction

(c)     South-west direction                                  (d) north-south direction

      Ans: north-south direction

5.      A device, which generally does not use a magnet, is-

(a)   A CD player                                    

(b)   A telephone

(c)    A geyser

(d)   An electric motor

      Ans: a geyser

D.     ANSWER THE FOLLOWING QUESTIONS IN BRIEF.

 

1.      State any two properties of a bar magnet.

Ans: Two properties of a bar magnet are, attractive property and directive property.

2.      Maximum iron filling stick to the two ends of a bar magnet. Why?

Ans: The magnetic strength is maximum at the two ends of a bar magnet. So, maximum iron fillings stick to the two ends of a bar magnet.

3.      Suppose we bring the north pole of one bar magnet towards the north pole of another freely suspended bar magnet. What are we likely to observe?

Ans: When we bring the north pole of one bar magnet towards the north pole of another freely suspended bar magnet, we will observe that the freely suspended magnet moves away. This is due to the fact that like poles repel each other.

4.      Two magnets X and Y, are placed as shown in the diagram. It is observed that magnet X floats above magnet Y. Give reason for this observation.

Ans: We know that the like poles of two magnets repel each other. Here also, the like poles of both the magnets are facing each other. Hence, the magnets are repelling each other. This is the reason the magnet X is floating above the magnitude Y.

5.      You are given a knitting needle made of steel. How can you make it into a magnet?

Ans: We can turn a knitting needle made of steel into a magnet by moving a bar magnet, along the length of the needle, a large number of times always in the same sense.

E.      ANSWER THE FOLLOWING QUESTIONS.

 

1.      Distinguish between the following:

(a)   Permanent magnet and temporary magnet

Ans: Permanent magnet: These magnets retain their magnetic properties for a longer duration. Permanent magnets can be made using steel, cobalt steel, alnico and ticanol.

Temporary Magnet: These magnets retain their magnetism for a shorter period of time. Electromagnets are a commonly used form of temporary magnets.

(b)   Magnetic and non-magnetic materials

Ans: Magnetic Materials: Materials which get attracted towards a magnet are called as magnetic materials. Examples are cobalt, iron, nickel etc.

Non-magnetic Materials: Materials which do not get attracted towards a magnet are called non-magnetic materials. Examples are wood, plastic etc.

2.      Two bar magnets, ‘P’ and ‘Q’ are kept as shown in the following diagram.

(a) If point ‘c’ represents the south pole of the magnet Q, which point represents the north pole of magnet P?

Ans: As the two magnets are repelling each other, so we can say that the point ‘b’ and ‘c’ represent the like poles. Therefore, point ‘b’ of the magnet ‘P’ is south pole. Thus, the point ‘a’ of the magnet ‘P’ represents the north pole.

(b) What will happen when the end ‘d’, of magnet ‘Q’ is brought towards the end ‘b’ of magnet ‘P’?

Ans: As ‘c’ represents the south pole, so ‘d’ of magnet ‘Q’ is the north pole. So, when the ‘d’ end of ‘Q’ is brought towards the end ‘b’ of magnet ‘P’, they will attract each other.

3.      Describe, in brief, the construction of a compass needle. State its main use.

Ans: ‘The compass’ consists of a magnetic needle pivoted at its centre and free to rotate a horizontal plane. The needle is fitted in a horizontal box having a glass cover. The compass also has a dial with directions marked on it.

The compass needle always points in N-S direction and thus can be used for finding direction.

4.      Draw a labelled diagram to show the ‘proper way of storing two bar magnets’, when they are not in use. State the advantage of such a ‘proper storing’.

Ans: Advantage of proper storage of magnets:

(i) helps in preserving the magnetism in a magnet

(ii) helps in prolonging the life of a magnet

5.      Write the different ways through which magnets can be made to lose their magnetism.

Ans: Magnets can lose their magnetism in the following ways:

(i) by improper storage

(ii) by heating

(iii) by dropping

(iv) by hammering

6.      Anushtha saw a steel clip at the bottom of a very shallow puddle of water. She used a magnet, to take out this clip, without wetting her hands, or the magnet. Describe how she must have done this.

Ans: A magnet can attract an iron object even from a distance. Hence, Anushtha used the attractive property of magnet.

STD-X, ELECTRICITY, PROBLEMS ON OHM'S LAW

 

1.  Calculate the potential difference required across a conductor of resistance 5 Ω to flow a current of 1.5 A through it.

 

ANS: Given, R = 5 Ω

                       I = 1.5 A

From Ohm’s law, V = IR = 1.5 x 5 = 7.5 V

 

2.  How much electric current is produced on applying p.d of 30 volts on a wire of resistance 20 Ω?

 

ANS: Given, R = 20 Ω

                      V = 30 V

According to Ohm’s law, V=IR

Therefore, I = V/R = 30/20 = 1.5 A

 

3.  If 5 ampere current flowing through a wire, develops a potential difference of 50 volts across its ends, find the resistance of the wire.

 

ANS: Given, I = 5 A

                      V = 50 V

Using Ohm’s law, V = IR

Therefore, R = V/I

                       = 50/5 = 10 Ω

 

4.  The p.d. between the terminals of an electric heater is 60 V when it draws a current of 4 A from the source. What current will the heater draw if the p.d. is increased to 120 V?

 

( As, current is directly proportional to Potential difference

So, as V is doubled (from 60 V to 120 V), current will also be doubled. So, the answer will be 2 x 4 = 8 A)

ANS: Given, V = 60 V

                       I = 4 A

According to Ohm’s law, V = IR

                                 So, R = V/I = 60/4 = 15 Ω

When the potential is increased to 120 V, the current is given by,

                                       I = V/R = 120/15 = 8 A

The current through the heater becomes 8 A.

 

5.  A relay with a resistance of 12 Ω is in an electric circuit with one side at a potential of 85 volts and the other at 71 volts. How much current is in the relay?

 

ANS: The p.d. across the relay = V₂ – V₁ = 85 V – 71 V =  14 V

Therefore, the current in the relay, I = V/ R = 14/12 = 1.2 A

PROBLEMS FOR PRACTICE

6.  A lamp of resistance 80 Ω draw a current of 0.75 A. Find the line voltage.

7.  An electric heater draw a current of 5 A when connected to 220 V mains. Calculate the resistance of its filament.

8.  How much current will an electric heater draw from a 200 V source, if the resistance of the filament is 100 Ω?

9.  How much current does an electric heater draw from a 220 V line, if the resistance of the heater (when hot) is 50 Ω?

10.  A bulb when cold has 1 Ω resistance. It draws a current of 0.3 A when glowing from a source of 3 V. Calculate the resistance of the bulb when it is glowing and explain the reason for the difference in resistance.