First Unit Test Portion 2022_2023

Ch.1. The living world: Adaptations and Classification

Question 1:

Find my match!
 

'A' Group		'B' Group
(1)	Lotus	(a)	Flower and leaves attract insects
(2)	Aloe	(b)	Haustorial roots for absorption of food
(3)	Cuscuta	(c)	Adapted to live in deserts
(4)	Venus flytrap	(d)	Adapted to live in water

ANSWER:

'A' Group		'B' Group
(1)	Lotus	(d)	Adapted to live in water
(2)	Aloe	(c)	Adapted to live in deserts
(3)	Cuscuta	(b)	Haustorial roots for absorption of food
(4)	Venus flytrap	(a)	Flower and leaves attract insects

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Question 2:

Read the paragraph and answer the following questions.
I am a penguin. I live in polar region covered by snow. My abdomen is white. My skin is thick with a layer of fat underneath. My body is spindle-shaped. My wings are small. My toes are webbed. We live in flocks.
(a) Why is my skin white and thick and why is there a thick layer of fat underneath?
(b) Why do we live in flocks sticking close to each other?
(c) Which geographical region do I inhabit? Why?
(d) Which adaptations should you have to enable you to live permanently in the polar region? Why?

ANSWER:

a. Having black and white skin is a type of adaptation known as camouflaging. It is called counter-shading and makes it harder for both the predators and the prey to see penguins from all sorts of angles. The white chest of penguin protects them in the water by camouflaging them from being seen from below against the lighter sky coming through the waters surface. Their black backs help them blend in with the darker, deeper ocean waters below them, thus protecting them from their predators. They have thick layer of fat because it keeps them warm under such extreme cold conditions.

b. We know that penguins live in the coldest regions of earth and in order to find warmth and solace they remain in flocks with each other. In order to escape the extreme cold conditions, they nestle together to keep each other warm. 

c. Penguins are found in regions of Antarctica, South America, Africa and Australia. Many species can also be found in New Zealand and the sub-Antarctic islands. 

d. The following adaptations are required to survive in polar regions:

• black and white skin with a thick layer of fat beneath it
• skin should be covered with feathers
• small body with small wings
• presence of strong muscles in chest and wings

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Question 3:

Who is lying?
(a) Cockroach – I have five legs.
(b) Hen – My toes are webbed.
(c) Cactus – My fleshy, green part is a leaf.

ANSWER:

The cockroach is lying beacuse it has six legs and not five.
The cactus is also lying because its fleshy, green part is a stem and not a leaf.

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Question 4:

Read each of the following statements. Write a paragraph about adaptation with reference to each statement.
(a) There is extreme heat in deserts.
(b) Grasslands are lush green.
(c) Insects are found in large numbers.
(d) We hide.
(e) We have long ears.

ANSWER:

a. There is extreme heat in deserts and dry conditions prevail in this region. The animals and plants which are found in this region have special modifications which help them to survive in such environment. For example, cactus and acacia plants withstand hot and dry environment of the desert with the help of various modifications. They have thick cuticle on their leaf surface and their stomata are arranged in deep pits to minimise water loss by transpiration. They have special photosynthetic pathway, CAM in which stomata remains closed during day time. Their leaves are reduced to spines to minimise water loss, and photosynthetic functions are performed by flattened stems.
Similarly desert animals have adaptive features like- thick skin to prevent the loss of water, long legs with flat and cushioned soles, long and thick eyelashes and nostrils which are protected by folds of skin.

b. Grasslands are lush green due to the presence of diverse types of bushes and grasses. Grasses are tall so that animals like tiger, lion, elephant can remain hidden in them. Animals which are found in grasslands have adaptations like strong legs to run fast and capture their prey, claws, sharp and pointed canine. The herbivores which are found in this region have eyes below the forehead which gives them wide angle vision which protects them from predators.

c. Insects are found in large numbers because they have developed mechanisms which help them to survive even in harshest of environment. They are found in extreme conditions of deserts and Antartic region due to these modifications. For example grasshopper have long, strong hind legs that help them jump, house flies have sponging mouthparts to slurp up food, stinky bugs and walking sticks have the ability to camouflage.

​d. There are certain species which are able to hide themselves by blending their colour with that of the surrounding. This adaptive mechanism is termed as camouflage and is a method to protect oneself from the predators and prey. For example, grasshopper, lizards, butterflies, chameleon, frogs etc.

e. Animals with long ears are found in grasslands. It is an adaptive mechanism which enables them to receive sounds from long distances and from different directions. Another important function of long ears is that they act as a cooling system. 

The large ears have thin skin and contain an extensive network of blood vessels that provide a large surface area for heat exchange. These vessels swell when the animal is hot to allow the blood to cool and contract when temperatures drop to conserve heat.

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Question 5:

Answer the following.
(a) Why is the camel called the 'Ship of the desert'?
(b) How can the plants like cactus and acacia live in deserts with scarce water?
(c) What is the inter-relationship between adaptations of organisms and their surroundings?
(d) How are organisms classified?

ANSWER:

a. Camel is called the "Ship of Desert" because it is the only means of transport found in deserts. The body of a camel has undergone various modifications that help it to survive in the hot and dry conditions of the deserts.

• Camels have very long legs that help them to walk in the sand and prevent the heat of the sand from reaching their bodies. 
• They have a prominent back or hump. It stores food which helps it to survive without food in the deserts for several days.
• Another important adaptation that helps the camel to survive in the desert is its ability to conserve water. They do not sweat and excrete only small amounts of water through urine. The camel dung is dry and devoid of water.
• All this helps the camel to conserve water and enables them to live without water for several days.

b. Cactus and acacia plants withstand hot and dry environment of the desert with the help of various modifications. They have thick cuticle on their leaf surface and their stomata are arranged in deep pits to minimise water loss by transpiration. They have special photosynthetic pathway, CAM in which stomata remains closed during day time. Their leaves are reduced to spines to minimise water loss and photosynthetic functions are performed by flattened stems.

c. Adaptation is defined as the modification or change in the organism's body or behaviour that helps it to survive in a particular environment. The environment in which an animal survives consists of many different things and it must learn to adapt to each of these factors in order to survive. These factors can be in the form of climate, the kinds of food plants that grow in it, other animals that may be predators or competitors etc. This fact is evident from the following examples:

• Cactus has thick cuticle on their leaf surface and their stomata are arranged in deep pits to minimise water loss by transpiration. They have special photosynthetic pathway, CAM in which stomata remains closed during day time. Their leaves are reduced to spines to minimise water loss, and photosynthetic functions are performed by flattened stems.
• Camels have very long legs that help it to walk in the sand and prevent the heat of the sand from reaching their bodies. The camel has a prominent back or hump. It stores food which helps it to survive without food in the deserts for several days.

d. The hierarchy of classification was developed by Carolus Linnaeus. It refers to the organisation or classification of organisms in the order of rank or importance. According to this system, kingdom is the highest rank. It is divided into phyla or divisions, which are further subdivided into classes. Further divisions include order, family, genus and species, in that order. Thus, species is the basic unit of classification.

Std.VI Ch.1.Natural Resources

Question 1:

Fill in the blanks.
(a) The layer of ozone gas absorbs ………… rays that come from the sun to the earth.
(b) Of the total water available on the earth, fresh water forms ...... percent.
(c) Both ...…. and ……... constituents are present in the soil.

ANSWER:

(a) The layer of ozone gas absorbs UV rays that come from the sun to the earth.
(b) Of the total water available on the earth, fresh water forms 0.3 percent.
(c) Both biotic and abiotic constituents are present in the soil.

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Question 2:

Why is it said that – ?
(a) The ozone layer is a protective shell of the earth.
(b) Water is life.
(c) Seawater is useful even though it is not potable.

ANSWER:

a. The ozone layer acts as a protective layer for life on the earth because it absorbs harmful ultraviolet radiations of the sun. These radiations, if reach the Earth’s surface, can cause skin cancer.

b. Water is one of the most precious resource which we have on earth. All the biochemical processes which occur in plants and animals, our surroundings etc. require water to function. It is required for the existence of life on earth as it is an essential component of all the biological processes. We cannot imagine our lives without the presence of water. 

c. Although sea water is not potable, it has various other kinds of uses which prove its importance:

• Water from oceans can be used for making hydroelectricity, a form of renewable source of energy.
• It can be used as a cheap transport method.
• They can be used for the activities like scuba diving, water sports etc. which is a means of boosting the tourism and economic growth of a country.
• Nuclear power plants require coolants like water to bring down the temperature of the reactors. For this purpose several gallons of water is required and this demand is fulfilled by the water from oceans.
• They support a variety of flora and fauna which have both ecological and economical value.

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Question 3:

What will happen if –
(a) Microbes in the soil get destroyed.
(b) The number of vehicles and factories in your surroundings increases.
(c) The total supply of potable water is finished.

ANSWER:

a. Soil contains various kinds of microbes like bacteria, fungi, algae, protozoa etc. All of these microorganisms play an important roles like:

• Certain bacteria and blue-green algae have the ability to fix atmospheric nitrogen. This, in turn, enriches the fertility of soil. Such microorganisms are known as biological nitrogen-fixers. Example − Rhizobium is a symbiotic bacterium which lives in the root nodules of leguminous plants. Rhizobium fixes atmospheric nitrogen into nitrogenous compounds.
• The bacteria and fungi present in soil decompose dead organic wastes of plants and animals, and convert them into manure. The manure contributes to the humus content of the soil, thereby helping in increasing its fertility.
• Not only these, microorganisms which are found in soil are also a part of many biogeochemical cycles which would not take place in their absence.

The above points explain the fact that how important microbes are and if they are destroyed its effect can be irreversible.

b. Vehicles and factories are the major sources of air pollution. If the number of vehicles and factories increase in our surroundings, it is obvious that it would result in increased levels of air pollution. Not only air pollution but they also result in noise pollution. In case, the no. of industries increase in our surrounding it means, more trees would have to be cut down to make way for them and thus resulting in damage to the environment.

c. If the total supply of potable water is finished then the life on earth will end. Water is required for the existence of living beings and in its absence, it owuld hamper their developemnt process and their survival.

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Question 4:

Match the following.
 

Group ‘A’		Group ‘B’
(1)	Carbon dioxide	(a)	Generation of soil
(2)	Oxygen	(b)	Rain
(3)	Water vapour	(c)	Plants and food production
(4)	Microbes	(d)	Combustion

ANSWER:

Group ‘A’		Group ‘B’
(1)	Carbon dioxide	(c)	Plants and food production
(2)	Oxygen	(d)	Combustion
(3)	Water vapour	(b)	Rain
(4)	Microbes	(a)	Generation of soil

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Question 5:

Name the following.
(a) Constituents of the biosphere
(b) Biotic constituents of soil
(c) Fossil fuel
(d) Inert gases in air
(e) Gases that are harmful to the ozone layer

ANSWER:

(a) Constituents of the biosphere- hydrosphere and atmosphere
(b) Biotic constituents of soil- microorganisms and insects
(c) Fossil fuel- coal and petroleum
(d) Inert gases in air- oxygen and nitrogen
(e) Gases that are harmful to the ozone layer- carbon tetrachloride

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Question 6:

True or false?
(a) Land and soil are the same thing.
(b) The water in a lake is called ground water.
(c) It takes about 1000 years to form a 25 cm thick layer of soil.
(d) Radon is used in decorative lights.

ANSWER:

(a) Land and soil are the same thing.- False
(b) The water in a lake is called ground water.- Flase
(c) It takes about 1000 years to form a 25 cm thick layer of soil.-False
(d) Radon is used in decorative lights.- False

Page No 8:

Question 7:

Answer in your own words.
(a) Explain with the help of a diagram how soil is formed.
(b) Why is there a shortage of water even though it occupies about 71% of the earth’s surface?
(c) What are the various constituents of air? Write their uses.
(d) Why are air, water and land considered to be valuable natural resources?

ANSWER:

a. Soil is formed by the process of weathering during which rocks break down to form soil particles. This breaking down of rock occurs over a period of millions of years. Weathering can be physical, chemical, and biological. The bedrock breaks down into pieces due to the effects of heat, cold, water, wind and rain. Microbes, insects and rodents also help iin this process. The roots of trees also help in the process of weathering.




b. Although water occupies about 71% of the earth's surface, all of it is not potable water. Most of the water is available in the form of seas and oceans which is salty in nature. This saline water has its limitations and cannot be used for many purposes. Around 2.7% of water exists in frozen state or as groundwater which is unaccessible. Only 0.3% of water is available as potable water which is fit for human consumption.

c.

Constituents of air	Uses
1. Nitrogen	Required in building proteins. Useful in production of ammonia. Used in airtight packaging of food products.
2. Oxygen	Necessary for respiration and combustion.
3. Carbon dioxide	Used by plants to make their foods. Used in fire extinguishers.
4. Argon	Used in electric bulbs.
5. Heluim	Used for obtaining low temperatures. Used for generating lifts in airships.
6. Neon	Used in decorative lights and street lighting.
7. Krypton	Used in fluorescent tubes.
8. Xenon	Used in flash photography.

d. The following points elucidate the fact that air, land and water are valuable natural resources:


Importance of air:

• The importance of air can be understood by the fact that earth supports life becuase of the present of this air in our surrounding.
• It is required for various biological functions and biogeochemical cycles.

Importance of land:

• All terrestrial organisms live on land.
• We use it for the purpose of land farming, building houses, roads etc.
• The plants and animals which we use also grow on the land.
• The minerals which we obtain from deep inside the earth are also important resources. For example, petrol, coal etc.

Importance of water:

• Water plays an important role in various vital processes that are carried out by our body. All cellular processes take place in water medium.
• The availability of water plays an important role in deciding the number of individuals of each species that will be able to survive in a particular area, and also the sustainability of life in the region. 
• Fresh water is utilized by humans for consumption. 
• Water is central to the lives of aquatic animals which live in water.

EVS I: Chapter 01- Our Earth and Our Solar System

Std.V Roman Numerals

Thank You

UNIVERSE

QUESTIONS AND ANSWERS

Fun with magnets

1. How will you do this?

Question a.
Determine whether a material is magnetic or non-magnetic.
Answer:

1. To determine whether the material is magnetic or non-magnetic, a magnet is moved over it.
2. If the material sticks to the magnet, it is called magnetic material.
3. If the material does not stick to the magnet, it is non-magnetic.

Question b.
Explain that a magnet has a certain magnetic field.
Answer:

1. The space around a magnet in which the magnetic force is active is called the magnetic field.
2. Place a white paper on a drawing board and place a bar magnet in the middle of the paper.
3. Spread the iron filings on the sheet and gently tap the sheet.
4. The iron filings arrange around the magnet in definite curved lines forming a symmetric pattern.
5. The lines are closer to each other near the poles and less crowded in the middle region around the magnet.
6. Beyond a particular region, the iron filings, will not get attracted.
7. The region where iron filings are attracted is the magnetic field of the magnets.

Question c.
Find the north pole of a magnet.
Answer:

1. Take a bar magnet. Tie a thread to the centre of a bar magnet and hang it from a stand.
2. Note the direction in which the magnet settles and turn it around again.
3. Allow it to settle and note the direction.
4. The end of the magnet that points to the north is called the north pole, while the end that points to the south is called the south pole.
5. The north pole is indicated by ‘N’ and the south pole by ‘S’.

2. Which magnet will you use?

Question a.
Iron is to be separated from a trash.
Answer:

1. Sharp and heavy iron scrap material is attached to a big disc.
2. The disc is a magnet and all scrap is attracted to it.
3. It is not possible to create, store such a big size magnet. Therefore magnetism is induced in the disc with the help of electricity.

An electromagnet is used which is attached to a crane for loading and unloading, transporting scrap and loose iron material from a trash.

Question b.
You are lost in a forest.
Answer:

1. If we are lost in a forest, we should take help of a mariner’s compass which will help us to find the directions while travelling through unknown regions.
2. If mariner’s compass is not available, a bar magnet when suspended in the centre will rest in north-south direction.

Question c.
A window shutter opens and shuts continuously in the wind.
Answer:
A bar magnet can be attached to the window pane so that the window will be closed tight during strong winds also.

3. Fill in the blanks with appropriate word.

Question a.
If a bar magnet is hung by a thread tied at its centre, its north pole becomes steady in the direction of the …………… pole of the earth. (south, north, east, west)
Answer:
North

Question b.
If a bar magnet is cut into equal pieces by cutting it at right angles to its axis at two pieces …………… bar magnets are formed, and a total of …………… poles are formed. (6,3,2)
Answer:
3, 6

Question c.
There is a repulsion between the …………… poles of a magnet and attraction between its ……………. poles. (opposite, like.)
Answer:
like, opposite

Question d.
When magnetic material is taken close to a magnet, the material acquires …………… . (permanent magnetism, induced magnetism, temporary, magnet keeper)
Answer:
induced magnetism

Question e.
If a magnet attracts a piece of metal, that piece must be made of ………… .(any other metal but iron, magnetic material or iron, non-magnetic material, electromagnets)
Answer:
magnetic material or iron

Question f.
A magnet remains steady in a ………….. direction. (east-west, north-south,)
Answer:
north-south

4. Write the answers in your words.

Question a.
How is an electromagnet made?
Answer:
1. To make an electromagnet we need the following apparatus; An iron nail of 10 cm length, 1 metre long insulated copper wire, a battery cell, pins.
2. Wind the copper wire around the nail as shown in the figure. Connect the free ends of the wire to the two terminals of a cell through a plug key.
3. Close the key to complete the circuit.
4. Bring small pins near the tip of the nail and observe.
5. When the circuit is completed, the iron pins are attracted by the nail and hence, they stick to the nail.

6. When the circuit is broken, the pins fall off.
7. A magnet is prepared by passing an electric current through an insulated wire wound around the iron nail. This is an electromagnet.
8. When the current is allowed to pass, the nail becomes a magnet and attracts pin / pins stick to it.
9. When the current is put off the nail does not behave as a magnet and therefore, pins fall off.
10. The magnetism is temporary in the case of an electromagnet.

Question b.
Write the properties of a magnet.
Answer:
Magnet possess following properties/ characteristics.

1. Magnet always settles in the north-south direction.
2. The magnetic force is concentrated at the two ends or poles of a magnet.
3. If a magnet is divided into two parts, two independent magnets are formed. It means that the two poles of a magnet cannot be separated from each other.
4. A magnetic material acquires magnetism when placed near a magnet. This magnetism is called induced magnetism.
5. There is repulsion between like poles of a magnet, while there is attraction between the opposite poles.

Question c.
What are the practical uses of a magnet?
Answer:

1. Magnets are materials to which objects made from iron, nickel, cobalt are attracted. But man explored magnets and its properties and made his life comfortable.
2. Permanent Magnets: are used in caps of pin holders, doors of fridges, doors of cupboards etc.
3. Temporary magnets: Electromagnets are used in electric bells, circuit of various machines, ATM card swipe machines, MRI- Magnetic Resonance Image, loudspeakers, electric cranes, microphones, Mariner’s compasses, etc.

Activity

Question 1.
Collect information regarding how the various magnets used in our day-to-day tasks are produced.

Question 2.
Collect information about the magnetism of the earth.

Fill in the blanks.

Question 1.
Iron objects ………….. to a magnet.
Answer:
stick

Question 2.
A magnet is used in ………….. and ………….. .
Answer:
gadgets and machines

Question 3.
The materials that stick to a magnet are called ………….. materials.
Answer:
magnetic

Question 4.
Materials that do not stick to a magnet are called ………….. materials.
Answer:
non-magnetic

Question 5.
When a magnet attracts an object, that object is ………….. due to the magnetic force.
Answer:
displaced

Question 6.
Magnetism is a form of ………….. .
Answer:
energy

Question 7.
A magnet always settles in the ………….. direction.
Answer:
north-south

Question 8.
The north pole is indicated by’ …………… and the south pole by ‘……………’.
Answer:
‘N’-‘S’

Question 9.
The end of the magnet that points to the north is called the ………….. .
Answer:
Northpole

Question 10.
The end of the magnet that points to the south is called the ………….. .
Answer:
South pole

Question 11.
The magnetic force is concentrated at the two ends or ………….. of a magnet.
Answer:
poles

Question 12.
If a magnet is divided into two parts, two ………….. magnets are formed.
Answer:
independent

Question 13.
It means that the two poles of a magnet cannot be ………….. from each other.
Answer:
separated

Question 14.
A magnetic material acquires magnetism when placed near a
Answer:
magnet

Question 15.
Iron filling stick to the iron bar when the ………….. is near it.
Answer:
magnet

Question 16.
There is ………….. between like poles of a magnet.
Answer:
repulsion

Question 17.
There is ………….. between the opposite poles of a magnet.
Answer:
attraction

Question 18.
Magnetic objects ………….. magnetism.
Answer:
induce

Question 19.
Material ………….. is a mixture of aluminium, nickel and cobalt.
Answer:
Alnico

Question 20.
………….. magnets are made from a mixture of nickel, cobalt and iron.
Answer:
Permanent

Question 21.
The bar of soft or pure iron which protects a magnet is called ………….. .
Answer:
magnet keeper

Question 22.
Magnetism gets ………….. when a magnet is heated, thrown, knocked about or broken into pieces.
Answer:
destroyed

Question 23.
Electromagnetic energy is used in our ………….. life.
Answer:
day-to-day

Question 24.
The metals iron, cobalt, nickel are ………….. materials.
Answer:
magnetic

Question 25.
………….. is a natural magnet.
Answer:
Magnetite

Match the columns.

Question a.

Column ‘A’	Column ‘B’
1. Iron, nickel, cobalt	(a) Electromagnet
2. Door bell magnet	(b) Permanent magnet
3. Nickel, cobalt, aluminium	(c) Magnetic metal
4. Cupboard magnet	(d) Mariner’s compass
5. Lodestone	(e) Alnico

Answer:

Column ‘A’	Column ‘B’
1. Iron, nickel, cobalt	(c) Magnetic metal
2. Door bell magnet	(a) Electromagnet
3. Nickel, cobalt, aluminium	(e) Alnico
4. Cupboard magnet	(b) Permanent magnet
5. Lodestone	(d) Mariner’s compass

State whether true or false. If false, correct the statement.

Question 1.
Material alnico is a mixture of aluminium, nickel and iron.
Answer:
False: Material alnico is a mixture ofaluminium, nickel and cobal.

Question 2.
Magnetism of electromagnet is permanent.
Answer:
False: Magnetism of electromagnet is temporary.

Question 3.
The bar of soft or pure iron protects the magnet.
Answer:
True

Question 4.
Like poles attract each other and unlike poles repel each other.
Answer:
False: Like poles repel each other and unlike poles attract each other.

Question 5.
The magnetic force is concentrated at the centre of the magnet.
Answer:
False: The magnetic force is concentrated at the poles of the magnet

Question 6.
Magnetism is a kind of energy.
Answer:
True

Question 7.
Mariner’s compass is used for finding directions while travelling.
Answer:
True

Question 8.
Cobalt is a magnetic material.
Answer:
True

Question 9.
The north pole is indicated by ‘S’ and the south pole is indicated by ‘N’.
Answer:
False: The north pole is indicated by Wand the south pole is indicated by ‘S’.

Question 10.
Electromagnetism is used in many places in our day-to-day life.
Answer:
True

Answer the following questions in one sentence.

Question 1.
What is a magnet?
Answer:
The material to which objects made from iron, nickel, cobalt get attracted is called as magnet.

Question 2.
What is magnetism?
Answer:
The property of a material to which objects made from iron, nickel, cobalt get attracted is called as magnetism.

Question 3.
What are magnetic materials?
Answer:
Materials that stick to a magnet are called magnetic materials, e.g. cobalt, nickel, iron.

Question 4.
What are non-magnetic materials?
Answer:
Materials that do not stick to a magnet are called non-magnetic material, e.g. plastic, rubber, glass etc.

Question 5.
What are lodestones?
Answer:
Lodestones are leading stones which are used for finding the directions while travelling through unknown regions.

Question 6.
How is magnetism a kind of energy?
Answer:
Work is done by magnetic force. Thus, magnetism is a kind of energy.

Question 7.
What is an electromagnet?
Answer:
When magnetism is produced in the iron due to the electric current, it is called an electromagnet.

Question 8.
How are permanent magnets made?
Answer:
Permanent magnets are made from a mixture of nickel, cobalt and iron.

Question 9.
List the instruments where electromagnets are used.
Answer:
Electromagnets are used in doorbells, cranes, loudspeakers, voltameters, TVs, antennas, radios etc.

Question 10.
How is magnetism destroyed?
Answer:
When magnets are heated, thrown, knocked about or broken into pieces, magnetism gets destroyed.

Question 11.
What is a magnet keeper?
Answer:
A magnet keeper is a bar of soft or pure iron which protects a magnet. It is a piece of soft iron placed in the box in which a magnet is kept.

Question 12.
Magnets exist in variety of shapes.
Answer:
Today, magnets are used in many machines, gadgets and devices. They are all man-made. Hence, they can have a variety of shapes depending upon their use.

Answer the following briefly.

Question 1.
What are leading stones?
Answer:

1. It was known quite long ago to the people in China and Europe that a piece of magnetite, hung freely always settled in the north-south direction.
2. These rocks then came to be used for finding the directions while travelling through unknown regions.
3. That is why they are called leading stones or Lodestones.

Question 2.
What has led to the invention of the Mariner’s compass?
Answer:
Leading stones have led to the invention of the mariner’s compass.

Question 3.
List the different shapes of magnets.
Answer:

1. Magnets have a variety of shapes depending on their uses.
2. They are bar magnets, disc magnets, horseshoe magnets, ring shaped magnets, cylindrical magnets, and small button magnets.

Question 4.
What are permanent magnets?
Answer:

1. Magnets which do not lose their magnetism easily are called permanent magnets or Magnets which are made up of magnetic substances are permanent magnets.
2. e.g. Magnets fixed in a pin holder, magnets of a door of a cupboard are permanent magnets.
3. Permanent magnets are made from a mixture of
   • Nickel, cobalt, iron
   • Aluminium, nickel, cobalt – alnico

Give scientific reasons.

Question 1.
Why is it important to place a magnet keeper in a box along with magnets?
Answer:
Magnetism gets destroyed when a magnet is heated, thrown, knocked about or broken into pieces. A magnet keeper which is a bar of soft or pure iron protects a magnet.

Question 2.
Cranes with magnets are used.
Answer:
When a magnet attracts an object, that object is displaced due to the magnetic force. In factories, ports, garbage depots, large objects are lifted and shifted from place to place using cames. Hence cranes are fitted with magnets.

Can you tell?

Question 1.
Pins in a pin holder do not fall? While we are shutting the door of a fridge, we find that it closes automatically from certain distance and does not open unless pulled again.
Answer:
Magnet is fitted in the cap of a pin holder and in the door of a fridge. Iron objects stick to the magnet.

Question 2.
Take a magnet from the laboratory and bring it near various objects in your use. Which of them stick to the magnet? What material is each of them made of? Observe these things carefully. Classify the objects into two groups: those which stick to the magnet, those which do not.
Comb, table, cupboard – iron, spoon, scissors, pen, pencil, eraser, books, mobile, laptops, glass bangles, hair pin, cupboard handle, chair, steel lunch box, magnetic stickers, toys, gold ring.
Answer:

Stick to the magnet	Doesn’t stick to the magnet
Iron cupboard, spoon, scissors, hairpin, steel lunch box, magnetic stickers	Comb, table, pen, pencil, eraser, books, glass bangles, chair, mobile, laptops, cupboard handle, toys, gold ring

Question 3.
Take a mixture of sand, pieces of paper, sawdust, iron filings and pins in a saucer and pass a magnet around the mixture. What do you see?
Answer:
When magnet is moved over a mixture of sand, pieces of paper, sawdust, iron filings and pins, pins and iron filings will cling to the magnet. Sand, sawdust and pieces of paper will remain behind.

Question 4.
How is a Mariner’s Compass used?
Answer:

1. A Mariner’s Compass is a magnetic needle used in navigation to show direction by deflections.
2. It is a direction-finding instrument used in navigation.
3. It is placed on the maps, grounds, decks as it will point to the magnetic north pole.
4. It has two or more magnets permanently attached to a compass card which moves freely on a pivot.
5. The needle fixed on the compass bowl indicates the ship’s heading position.

Question 5.
Find out where the magnet given are used?
Answer:

Magnets	Uses
Horseshoe magnet	used in electric bell
Circular magnet	used in loudspeaker.
Magnetic needle	used in Mariner’s Compass.
Disc magnets	used in toys
Bar magnets	used in cupboard doors
Button magnet	supporting side rails or blockouts
Square magnet	Industries
Arc magnet	Electric motors and generators.
Cylindrical magnet	used in medicine, used in treatment of scoliosis patients.

Question 6.
Identify the different types of magnets as shown in the picture below.
Answer:
a. Circular magnet
b. Cylindrical magnet
c. Horseshoe magnet
d. Bar magnet