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Thursday, 31 October 2013
Sunday, 27 October 2013
Ch 16 : Garbage In Garbage Out
CBSE Class 6 - Science - CH 16 - Garbage In Garbage Out
Q1: Fill in the blanksAnswer:
1. Converting plant and animal waste including that from kitchen, into manure, is called composting.
2. A garbage dump is also used as landfill.
3. The method of making compost from kitchen garbage using redworms is called vermicomposting.
4. Consuming food packed in such plastic bags could be harmful to our health.
Q2: (a) Which kind of garbage is not converted into compost by the redworms?
(b) Have you seen any other organism besides redworms, in your pit? If yes, try to find out their names. Draw pictures of these.
1. Converting plant and animal waste including that from kitchen, into manure, is called composting.
2. A garbage dump is also used as landfill.
3. The method of making compost from kitchen garbage using redworms is called vermicomposting.
4. Consuming food packed in such plastic bags could be harmful to our health.
Q2: (a) Which kind of garbage is not converted into compost by the redworms?
(b) Have you seen any other organism besides redworms, in your pit? If yes, try to find out their names. Draw pictures of these.
 |
| redworms - friends of farmers |
Answer: Non bio-degradable waste like pieces of cloth, polythene bags, broken glass, aluminium wrappers, nails, old shoes and broken toys cannot be converted into compost by the redworms.
(b) Besides redworms there are spiders, small bugs, flies, moulds and small insects etc. can be seen in the pit. Compost is also rich of microbes which can't be seen with unaided eye.
Q3: Discuss:
(a) Is garbage disposal the responsibility only of the government?
(b) Is it possible to reduce the problems relating to disposal of garbage?
Answer:
(a) Garbage Disposal is the responsibility of every citizen. If we continue to generate so much garbage, very soon our beautiful earth will convert into a big garbage-bin. Non-biodegradable waste like plastic is harmful to our environment as well as to our health. We must ensure ways to reduce production of garbage. Wherever possible, we must use recyclable material in our daily use.
(b) Yes it is possible to reduce the problems relating to disposal of garbage to a large extent. We should use those materials which are recyclable. We should avoid or reduce the use of non-biodegradable materials at minimum level. While throwing out garbage in trash can, we should separate biodegradable waste from non-biodegradable and throw them in separate bins.
Q4: (a) What do you do with the left over food at home?
(b) If you and your friends are given the choice of eating in a plastic plate or a banana leaf platter at a party, which one would you prefer and why?
Answer: (a) Left over food can be collected and be converted into compost. We can feed our pet animals with left over food. If enough food is left (e.g. after a party), we may distribute the food to shelter homes.
(b) Banana leaf is a better choice. It is bio-degradable and can be disposed easily. On the other hand, eating in plastic plate is not good. Plastic material may contain harmful substance which can make the contained food toxic. which is harmful to our health. Also plastic is non-biodegradable, it will not dispose off easily.
Q5: (a) Collect pieces of different kinds of paper. Find out which of these can be recycled.
(b) With the help of a lens look at the pieces of paper you collected for the above question. Do you see any difference in the material of recycled paper and a new sheet of paper ?
Answer:
(a) Almost all kinds of paper are recyclable i.e. newspapers, magazines, papers, notebooks, envelopes etc.
(b) The difference between new sheet and recycle paper is subtle. Usually hand made recycled paper is of coarse quality.
Q6: (a) Collect different kinds of packaging material. What was the purpose for which each one was used? Discuss in groups.
(b) Give an example in which packaging could have been reduced?
(c) Write a story on how packaging increases the amount of garbage.
Answer:
(a) Different kinds of packaging materials used commonly are:
- Cardboard - used as shoe boxes
- Plastic Bags - Toys covers, sarees bags
- Wooden Boxes - Fruit baskets
- Jute Bags - School bags, shopping bags
(b) Since plastic is
harmful to our environment and is non-biodegradable. We should avoid using
plastic packaging.
(c) The basic purpose of packaging is to protect the product from tampering and to maintain its freshness. However, most of the packaging material is used to beautify the boxes and make them look attractive on the shelves. Unfortunately a large volume of packaging material goes waste and is thrown into dustbin. For example, if you go to any park, there dustbins are full of potato chips wrappers. It unnecessarily increases the amount of garbage. It also increase the cost of the product due to unnecessary packaging. We should seriously consider how to reduce unnecessary packaging. We should prefer buy products carry less packaging material.
Q7: Do you think it is better to use compost instead of chemical fertilisers? Why?
Answer: No doubt compost is better to use than chemical fertilizers due to following reasons:
(c) The basic purpose of packaging is to protect the product from tampering and to maintain its freshness. However, most of the packaging material is used to beautify the boxes and make them look attractive on the shelves. Unfortunately a large volume of packaging material goes waste and is thrown into dustbin. For example, if you go to any park, there dustbins are full of potato chips wrappers. It unnecessarily increases the amount of garbage. It also increase the cost of the product due to unnecessary packaging. We should seriously consider how to reduce unnecessary packaging. We should prefer buy products carry less packaging material.
Q7: Do you think it is better to use compost instead of chemical fertilisers? Why?
Answer: No doubt compost is better to use than chemical fertilizers due to following reasons:
- Compost is much easier to prepare.
- Compost is environment friendly whereas fertilizers can harm our health and the environment.
- Compost does not pollute our environemnt.
- Compost decomposes bio-degradable waste into natural soil. It conserves our environment.
Q8: How do redworms prepare
vermicompost?
Answer: Red worms have a special structure called gizzards in their bodies with which they grind food material and covert it into manure.
Q9: What will happen if garbage is not disposed off?
Answer: If garbage is not properly disposed off, these garbage dumps turn into breeding grounds for micro-organisms, flies, cockroaches and mosquitoes, that may cause diseases.
Q10: Why is it illegal to burn leaves and other plant wastes?
Answer: Burning of leaves and other plant wastes produces smoke and gases that are harmful to
our health. They may lead to asthma and lung diseases. Instead of burning, these plant wastes must be converted into manure.
Q11: Why should we not throw plastic bags or wrappers carelessly on roads and other places?
Answer: The plastic bags thrown away carelessly on roads and other places get into drains and the sewer system. As a result, drains get choked and the water spills on the roads. During heavy rains,
it might even create a flood like situation.
Sometimes, these bags are eaten by stray animals like cows, dogs etc. These bags are toxic in nature and affect their health.
Answer: Red worms have a special structure called gizzards in their bodies with which they grind food material and covert it into manure.
Q9: What will happen if garbage is not disposed off?
Answer: If garbage is not properly disposed off, these garbage dumps turn into breeding grounds for micro-organisms, flies, cockroaches and mosquitoes, that may cause diseases.
Q10: Why is it illegal to burn leaves and other plant wastes?
Answer: Burning of leaves and other plant wastes produces smoke and gases that are harmful to
our health. They may lead to asthma and lung diseases. Instead of burning, these plant wastes must be converted into manure.
Q11: Why should we not throw plastic bags or wrappers carelessly on roads and other places?
Answer: The plastic bags thrown away carelessly on roads and other places get into drains and the sewer system. As a result, drains get choked and the water spills on the roads. During heavy rains,
it might even create a flood like situation.
Sometimes, these bags are eaten by stray animals like cows, dogs etc. These bags are toxic in nature and affect their health.
Ch 15 : Air Around Us
CBSE class 6 - Science - CH 15 - Air Around Us
Q1: What is the composition of air?
Answer: Air is a mixture gases, water vapours and dust particles. Largely it consists of:
Q2: What are the important properties of air?
Answer: Important properties of air are:
Q3: Which gas in the atmosphere is essential for respiration?
Answer: Oxygen is essential for living organisms.
Q4: How will you prove that air supports burning?
Answer: Place a burning candle in a tray. Cover it with a glass jar. To make it air-tight, fill tray with water. After sometime, burning candle dims and goes off. Water level also rises up in the jar. It shows air support burning.
Explanation: During burning, oxygen is consumed and carbon-dioxide is released. After sometime no oxygen is left inside the jar and flame goes out. Once the candle goes off, the temperature surrounding the candle cools down and volume of air (carbon dioxide) decreases. Thus water rises up little in the jar.
Q5: How will you show that air is dissolved in
water?
Answer: Take some water in a glass vessel or beaker. Heat it slowly on a tripod stand. Well before the water begins to boil, look carefully at the inner surface of the vessel. These bubbles come from the air
dissolved in water.
Q6: Why does a lump of cotton wool shrink in water?
Answer: Air is present in the cotton wool. When dipped in water, air present in wool escape and it shrinks.
Q7: Fill in the blanks:
Answer:
1. The layer of air around the earth is known as _atmosphere_.
2. The component of air used by green plants to make their food, is _carbon dioxide__.
3. Air occupies _space_.
4. Aquatic animals use _dissolved_ air in water for respiration.
Q8: List five activities that are possible due to the presence of air.
Answer:
Q9: How do plants and animals help each other in the exchange of gases in the atmosphere?
Answer: There is the interdependence of plants and animals. Both plants and animals respire i.e. they inhale oxygen and gives out carbon dioxide in the atmosphere. Plants take carbon dioxide from the atmosphere and prepare food. This is called photosynthesis. During this process, plants give out oxygen to the atmosphere. Therefore plants and animals help each other in the exchange of gases in the atmosphere.
Q10:Why do why earthworms come out of the soil, only during heavy rains?
Answer: Most of the small organisms like earth worms, rodents live inside the soil. They usually live in burrows and holes in the soil. These burrows also make spaces available for air to move in and out of the soil. However, when it rains heavily, water fills up all the spaces occupied by the air in the soil. In this situation, animals living in the soil have to come out for respiration.
Q11: What is the use of Nitrogen?
Answer: Nitrogen is used in protein synthesis. Nitrogen is an important constituent of amino-acids which manufacture proteins, Proteins are required by living organisms to grown and repair their body parts.
Q12: How Oxygen is removed from the atmosphere?
Answer:
Q1: What is the composition of air?
Answer: Air is a mixture gases, water vapours and dust particles. Largely it consists of:
- Nitrogen (79%)
- Oxygen (20%)
- Carbon Di-Oxide (1%)
- Other gases like Helium, Hydrogen etc.
- Water Vapours
- Dust particles
Q2: What are the important properties of air?
Answer: Important properties of air are:
- Air occupies space.
- Air is present every where including water and soil.
- Air is transparent.
- Air is colourless.
- Air is essential for life on earth.
Q3: Which gas in the atmosphere is essential for respiration?
Answer: Oxygen is essential for living organisms.
Q4: How will you prove that air supports burning?
Answer: Place a burning candle in a tray. Cover it with a glass jar. To make it air-tight, fill tray with water. After sometime, burning candle dims and goes off. Water level also rises up in the jar. It shows air support burning.
Explanation: During burning, oxygen is consumed and carbon-dioxide is released. After sometime no oxygen is left inside the jar and flame goes out. Once the candle goes off, the temperature surrounding the candle cools down and volume of air (carbon dioxide) decreases. Thus water rises up little in the jar.
Q5: How will you show that air is dissolved in
water?Answer: Take some water in a glass vessel or beaker. Heat it slowly on a tripod stand. Well before the water begins to boil, look carefully at the inner surface of the vessel. These bubbles come from the air
dissolved in water.
Q6: Why does a lump of cotton wool shrink in water?
Answer: Air is present in the cotton wool. When dipped in water, air present in wool escape and it shrinks.
Q7: Fill in the blanks:
Answer:
1. The layer of air around the earth is known as _atmosphere_.
2. The component of air used by green plants to make their food, is _carbon dioxide__.
3. Air occupies _space_.
4. Aquatic animals use _dissolved_ air in water for respiration.
Q8: List five activities that are possible due to the presence of air.
Answer:
- Animals use air for respiration.
- Plants use air to prepare their food. (photosynthesis)
- Power generation by wind mills.
- Burning of fuels and substances.
- Air helps in the scattering of seeds and pollens of plants. (pollination).
- Air helps in the movements of sailing yachts, gliders, parachutes and aeroplanes.
Q9: How do plants and animals help each other in the exchange of gases in the atmosphere?
Answer: There is the interdependence of plants and animals. Both plants and animals respire i.e. they inhale oxygen and gives out carbon dioxide in the atmosphere. Plants take carbon dioxide from the atmosphere and prepare food. This is called photosynthesis. During this process, plants give out oxygen to the atmosphere. Therefore plants and animals help each other in the exchange of gases in the atmosphere.
Q10:Why do why earthworms come out of the soil, only during heavy rains?
Answer: Most of the small organisms like earth worms, rodents live inside the soil. They usually live in burrows and holes in the soil. These burrows also make spaces available for air to move in and out of the soil. However, when it rains heavily, water fills up all the spaces occupied by the air in the soil. In this situation, animals living in the soil have to come out for respiration.
Q11: What is the use of Nitrogen?
Answer: Nitrogen is used in protein synthesis. Nitrogen is an important constituent of amino-acids which manufacture proteins, Proteins are required by living organisms to grown and repair their body parts.
Q12: How Oxygen is removed from the atmosphere?
Answer:
- Through combustion or burning of substances,
- Through respiration by living beings.
- Rusting of iron.
Ch 14 : Water
CBSE Class 6 - Science - CH14 - Water
Q1: Fill up the blanks in the following:(a) The process of changing of water into its vapour is called _________________.
(b) The process of changing water vapour into water is called _________________.
(c) No rainfall for a year or more may lead to _________________ in that region.
(d) Excessive rains may cause _________________.
(e) Water disappears from wet clothes by the process of ___________________.
(f) In winter mornings , __________is formed due to condensation of water vapour near the ground.
(g) The major natural source of water is _________________.
(h) Many tiny water droplets high up in the air, come together and fall down as _____________, __________ and ___________.
Answer:
(a) evaporation
(b) condensation
(c) drought
(d) flood
(e) evaporation
(f) fog
(g) oceans and sea
(h) rain, hail, snow
Q2: State for each of the following whether it is due to evaporation or condensation:
(a) Water drops appear on the outer surface of a glass containing cold water.(b) Steam rising from wet clothes while they are ironed.
(c) Fog appearing on a cold winter morning.
(d) Blackboard dries up after wiping it.
(e) Steam rising from a hot girdle when water is sprinkled on it.
Answer:
(a) Water drops appear on the outer surface of a glass containing cold water. - condensation
(b) Steam rising from wet clothes while they are ironed. - evaporation
(c) Fog appearing on a cold winter morning. - condensation
(d) Blackboard dries up after wiping it. - evaporation
(e) Steam rising from a hot girdle when water is sprinkled on it. - evaporation
Q3: Which of the following statements are “true” ?
Answer:
(a) Water vapour is present in air only during the monsoon. (False ✗)
(b) Water evaporates into air from oceans, rivers and lakes but not from the soil.(False ✗)
(c) The process of water changing into its vapour, is called evaporation.(True ✓)
(d) The evaporation of water takes place only in sunlight.(False ✗)
(e) Water vapour condenses to form tiny droplets of water in the upper layers of air where it is cooler.(True ✓)
(f) Life is possible on earth without water (False ✗)
(g) When water is heated, it changes into ice. (False ✗)
(h) Evaporation of water takes place at all times. (True ✓)
(i) Saline water is fit for drinking and other domestic, agricultural and industrial needs. (False ✗)
(j) About two-thirds of the earth is covered with water. (True ✓)
Q4: Suppose you want to dry your school uniform quickly. Would spreading it near an anghiti or heater help? If yes, how?
Answer: Yes, spreading school uniform near anghiti or heater would help dry it quickly. Heater will warm up the surroundings and increase the rate of evaporation. Therefore school uniform will dry up quickly.
Q5: Take out a cooled bottle of water from refrigerator and keep it on a table. After some time you notice a puddle of water around it. Why?
Answer: It is due to condensation of water vapours present in air. The cold surface of the bottle cools the air around it, and the water vapour of the air condenses on its surface.
Q6: To clean their spectacles, people often breathe out on glasses to make them wet. Explain why the glasses become wet.
Answer: When we breathe out, moist air comes out which make the glasses wet. Also when we breathe out, we release carbon-dioxide gas which cools the surroundings by absorbing heat from air, thus condenses the water vapours.
Q7: How are clouds formed?
Answer: Clouds are formed due to the process of evaporation and condensation. When air moves up, it gets cooler and cooler. At sufficient height, the air becomes so cool that water vapours present in the air condense. They form tiny droplets and float in air as clouds.
Q8:
When does a drought occur?
Answer: When there is insufficient or no rainfall occurs for more than a year in a region, the scarcity of water happens. Ponds and wells dry up. The soil continues to lose water due to evaporation and transpiration and eventually dry. This leads to drought.
Q9: What is rainwater harvesting? What are the two rainwater harvesting techniques?
Answer: Collecting rain water and storing it for later use is called rainwater harvesting. The two techniques of rainwater harvesting are:
Q10: Explain Water cycle with diagram.
Answer: The continuous journey of water in nature from earth to clouds and back to the earth is called water cycle. The water cycle mainly consists of following processes:
Q11: Explain how floods causes extensive damage to human life and property?
Answer:
Q12(MCQ): What do we see on the surface of the glass containing ice-chilled water ?
(a) dust
(b) water vapour
(c) water droplets
(d) ice
Answer: (c) water droplets
Q13(MCQ): Evaporation of water in shade is
(a) fast
(b) faster
(c) slow
(d) none of these
Answer: (b) faster
Q14(MCQ): The process of changing water into water vapours is called
(a) filtration
(b) condensation
(c) evaporation
(d) sedimentation
Answer: (c) evaporation
Q15(MCQ): How much water is consumed by a city-dweller in washing, bathing, flushing the toilet etc.?
(a) 2-3 litres
(b) 10-15 litres
(c) 100-300 litres
(d) 1000-1500 litres
Answer: (c) 100-300 litres
Q16(MCQ): If tap of your bathroom is leaking drop by drop, how much water is lost per day?
(a) 1 bucket full of water
(b) 2 buckets full of water
(c) 8 buckets full of water
(d) 20 buckets full of water
Answer: (c) 8 buckets full of water
Q1: Fill up the blanks in the following:(a) The process of changing of water into its vapour is called _________________.
(b) The process of changing water vapour into water is called _________________.
(c) No rainfall for a year or more may lead to _________________ in that region.
(d) Excessive rains may cause _________________.
(e) Water disappears from wet clothes by the process of ___________________.
(f) In winter mornings , __________is formed due to condensation of water vapour near the ground.
(g) The major natural source of water is _________________.
(h) Many tiny water droplets high up in the air, come together and fall down as _____________, __________ and ___________.
Answer:
(a) evaporation
(b) condensation
(c) drought
(d) flood
(e) evaporation
(f) fog
(g) oceans and sea
(h) rain, hail, snow
Q2: State for each of the following whether it is due to evaporation or condensation:
(a) Water drops appear on the outer surface of a glass containing cold water.(b) Steam rising from wet clothes while they are ironed.
(c) Fog appearing on a cold winter morning.
(d) Blackboard dries up after wiping it.
(e) Steam rising from a hot girdle when water is sprinkled on it.
Answer:
(a) Water drops appear on the outer surface of a glass containing cold water. - condensation
(b) Steam rising from wet clothes while they are ironed. - evaporation
(c) Fog appearing on a cold winter morning. - condensation
(d) Blackboard dries up after wiping it. - evaporation
(e) Steam rising from a hot girdle when water is sprinkled on it. - evaporation
Q3: Which of the following statements are “true” ?
Answer:
(a) Water vapour is present in air only during the monsoon. (False ✗)
(b) Water evaporates into air from oceans, rivers and lakes but not from the soil.(False ✗)
(c) The process of water changing into its vapour, is called evaporation.(True ✓)
(d) The evaporation of water takes place only in sunlight.(False ✗)
(e) Water vapour condenses to form tiny droplets of water in the upper layers of air where it is cooler.(True ✓)
(f) Life is possible on earth without water (False ✗)
(g) When water is heated, it changes into ice. (False ✗)
(h) Evaporation of water takes place at all times. (True ✓)
(i) Saline water is fit for drinking and other domestic, agricultural and industrial needs. (False ✗)
(j) About two-thirds of the earth is covered with water. (True ✓)
Q4: Suppose you want to dry your school uniform quickly. Would spreading it near an anghiti or heater help? If yes, how?
Answer: Yes, spreading school uniform near anghiti or heater would help dry it quickly. Heater will warm up the surroundings and increase the rate of evaporation. Therefore school uniform will dry up quickly.
Q5: Take out a cooled bottle of water from refrigerator and keep it on a table. After some time you notice a puddle of water around it. Why?
Answer: It is due to condensation of water vapours present in air. The cold surface of the bottle cools the air around it, and the water vapour of the air condenses on its surface.
Q6: To clean their spectacles, people often breathe out on glasses to make them wet. Explain why the glasses become wet.
Answer: When we breathe out, moist air comes out which make the glasses wet. Also when we breathe out, we release carbon-dioxide gas which cools the surroundings by absorbing heat from air, thus condenses the water vapours.
Q7: How are clouds formed?
Answer: Clouds are formed due to the process of evaporation and condensation. When air moves up, it gets cooler and cooler. At sufficient height, the air becomes so cool that water vapours present in the air condense. They form tiny droplets and float in air as clouds.
 |
| Drought credits:wikipedia |
Answer: When there is insufficient or no rainfall occurs for more than a year in a region, the scarcity of water happens. Ponds and wells dry up. The soil continues to lose water due to evaporation and transpiration and eventually dry. This leads to drought.
Q9: What is rainwater harvesting? What are the two rainwater harvesting techniques?
Answer: Collecting rain water and storing it for later use is called rainwater harvesting. The two techniques of rainwater harvesting are:
- Rooftop rainwater harvesting.
- Allowing water to into ground directly through roadside drains.
Q10: Explain Water cycle with diagram.
Answer: The continuous journey of water in nature from earth to clouds and back to the earth is called water cycle. The water cycle mainly consists of following processes:
- Evaporation and Transpiration
- Condensation
- Precipitation
- Accumulation
- When the sun heats up the water in rivers, ponds, oceans and lakes, it turns water into vapours. Plants also lose water into air due to transpiration.
- At sufficient heights, the water vapours in the air cool down and condense to form clouds
- Precipitation occurs when too much water vapours condense. The clouds become heavy and begin to fall as rain, hail or snow.
- The water falls on the earth, it goes into lakes, oceans, rivers and ground.
Q11: Explain how floods causes extensive damage to human life and property?
Answer:
- Droughts results in drying up of the crops and vegetation.
- Its leads to scarcity of food and fodder for humans and animal life.
- It leads to malnutrition in humans and animals.
Q12(MCQ): What do we see on the surface of the glass containing ice-chilled water ?
(a) dust
(b) water vapour
(c) water droplets
(d) ice
Answer: (c) water droplets
Q13(MCQ): Evaporation of water in shade is
(a) fast
(b) faster
(c) slow
(d) none of these
Answer: (b) faster
Q14(MCQ): The process of changing water into water vapours is called
(a) filtration
(b) condensation
(c) evaporation
(d) sedimentation
Answer: (c) evaporation
Q15(MCQ): How much water is consumed by a city-dweller in washing, bathing, flushing the toilet etc.?
(a) 2-3 litres
(b) 10-15 litres
(c) 100-300 litres
(d) 1000-1500 litres
Answer: (c) 100-300 litres
Q16(MCQ): If tap of your bathroom is leaking drop by drop, how much water is lost per day?
(a) 1 bucket full of water
(b) 2 buckets full of water
(c) 8 buckets full of water
(d) 20 buckets full of water
Answer: (c) 8 buckets full of water
Ch 13 : Fun With Magnets
Class 6 - Science - CH 13 - Fun with Magnets
Q2: State whether the following statements are true or false.
Answer:
The two ends of the bar magnet represents the two poles.
Magnetic compass works on the same principle. In past it was used by sailors or travellers to find directions.
Q8: You are given an iron strip. How will you make it into a magnet?
Q9: How is a compass used to find
directions?
Answer: The natural magnet is called magnetite.
Q12: Name the place it is believed where natural magnet was found first time.
Q1: Fill in the blanks in the
following:
Answer:
(i) Artificial magnets are made in
different shapes such as _bar-magnet_, _cylindrical_
and _horse-shoe magnet_.
(ii) The Materials which are
attracted towards a magnet are called_magnetic materials_.
(iii) Paper is not a
_magnetic_ material.
(Explanation: Paper does not
attract to magnet. Therefore it is a non-magnetic material).
(iv) In olden days, sailors used to
find direction by suspending a piece of _bar magnet_.
(v) A magnet always has
_two__ poles (i.e. North Pole and South Pole).
Q2: State whether the following statements are true or false.
Answer:
(i) A cylindrical magnet has only
one pole. - False (✗)
(ii) Artificial magnets were
discovered in Greece. - False - (✗)
(iii) Similar poles of a magnet
repel each other. - True - (✓)
(iv) Maximum iron filings stick in
the middle of a bar magnet when it is brought near them.- False - (✗)
(v) Bar magnets always point
towards North-South direction. - True -
(✓)
(vi) A compass can be used to find
East-West direction at any place. - True -
(✓)
(vii) Rubber is a magnetic
material. False - (✗)
Q3: It was observed that a
pencil sharpener gets attracted by both the poles of a magnet although its body
is made of plastic. Name a material that might have been used to make some part
of it.
Answer: The blade of the pencil sharpener is made of
iron. Iron is a magnetic in nature. That's why the sharpener gets attracted by
the poles of a magnet.
Q4: Column I shows different
positions in which one pole of a magnet is placed near that of the other. Column
II indicates the resulting action between them for each situation. Fill in the
blanks.
Answer: | Column I | Column II |
|---|---|
| N-N | Repulsion |
| N-_S_ | Attraction |
| S-N | Attraction |
| _N_-S | Repulsion |
Q5: Write any two properties of
a magnet.
Answer:
- Each magnet has two poles i.e. North Pole(N) and South Pole(P)
- Opposite poles of two magnet attract each other while like poles of two magnet repel each other.
- A freely suspended magnet always aligns in N-S direction.
 |
| Bar Magnet |
Q6: Where are poles of a bar magnet
located?
 |
| Magnetic Compass |
Q7: A bar magnet has no markings
to indicate its poles. How would you find out near which end is its north pole
located?
Answer: Hang up the magnet by a cotton thread so that
it hangs freely. When it comes to rest, we notice that the magnet is lying in a
North - South direction.
Magnetic compass works on the same principle. In past it was used by sailors or travellers to find directions.
Q8: You are given an iron strip. How will you make it into a magnet?
Answer:
- Take a rectangular piece of iron. Place
it on the table. - Take a bar magnet and place one of its poles near one edge of the bar of iron.
- Without lifting the bar magnet, move it along the length of the iron bar till you reach the other end.
- Lift the magnet and bring the pole (the same pole you started with) to the same point of the iron bar from which you began
- Move the magnet again along the iron bar in the same direction as you did
before. Repeat this
process about 30-40 times. - Bring few allpins near to the iron bar and check if it is converted to a magnet or not.
 |
| Compass Directions |
Answer: A magnetic compass consists of a small
pointed magnet which is suspended freely. A freely suspended magnet always
aligns in N-S direction. The red coloured magnetic needle points to North
direction. Once we know North direction, we can easily find out the other
directions.
E.g. If North is upwards, South is
downward side, East will be on right hand side and West shall be on left hand
side.
Q10: A magnet was brought from
different directions towards a toy boat that has been floating in water in a
tub. Affect observed in each case is stated in Column I. Possible reasons for
the observed affects are mentioned in Column II. Match the statements given in
Column I with those in Column II.
Answer:
| Column I | Column II |
|---|---|
| Boat gets attracted towards the magnet | Boat is made of magnetic material |
| Boat is not affected by the magnet | Boat is made up non-magnetic material |
| Boat moves towards the magnet if
north pole of the magnet is brought near its head |
Boat is fitted with a magnet with
south pole towards its head |
| Boat moves away from the magnet
when north pole is brought near its head |
Boat is fitted with a magnet with
north pole towards its head |
| Boat floats without changing its direction. | Boat has a small magnet fixed along
its length |
Q11: What is
magnetite?
Answer: The natural magnet is called magnetite.
Q12: Name the place it is believed where natural magnet was found first time.
Answer: Magnesia in Ancient Greece.
Q13: How magnets were
discovered?
Answer: There was a shepherd called Magnes who lived
in Ancient Greece. He used to carry a stick with iron piece attached to it while
taking his sheep for grazing to nearby mountains. One day he found his stick was
attracted to a rock. This was the way he discovered natural magnet.
Q14: What are magnetic
materials? Give two examples.
Answer: The materials which get attracted to magnets
are known as
magnetic materials.
magnetic materials.
Examples are: Iron, Nickel,
Cobalt
Q15: What are non-magnetic
materials? Give examples.
Answer: The materials which do not get attracted to
magnets are called non-magnetic materials.
Examples: Plastic, wood,
paper
Q16: How do magnets loose their
magnetic property?
Answer: Magnets lose their property on heating, hammering and dropping.
Q17: If a bar magnet is cut lengthwise into three parts, how many number of Poles will form?
Answer: Six (Three North and three south)
Answer: Magnets lose their property on heating, hammering and dropping.
Q17: If a bar magnet is cut lengthwise into three parts, how many number of Poles will form?
Answer: Six (Three North and three south)
Ch 12 : Electricity and Circuits
CBSE Class 6 - Science - CH 12 - Electricity and Circuits
Q1. Fill in the blanks :(a) A device that is used to break an electric circuit is called _______________.
(b) An electric cell has _______________ terminals.
(c) Electric cell is a device which converts energy of chemicals into ________________energy.
(d) The electric energy which is supplied in our home comes from electric _______________houses.
(e) An electric ______________ is a continuous path along which the current flows.
(f) If the filament of a bulb breaks, it is said to be ______________.
(g) Rubber is a good example of electric ______________.
Answer:
(a) switch
(b) two terminals
(c) electrical
(d) poles nearby
(e) circuit
(f) fused
(g) insulator
Q2: Mark 'True' or 'False' for following statements:
Answer:
(a) Electric current can flow through metals. (✓ True)
(b) Instead of metal wires, a jute string can be used to make a circuit. (✗ False)
(c) Electric current can pass through a sheet of thermocol. (✗ False)
(d) When current flows through a circuit, the circuit is called open circuit. (✗ False)
(e) An electric bulb has one terminal (✗ False)
Q3: What is an electric cell?
Answer: An electric cell is a device which converts chemical
energy into electric energy. It has two different metal plates:
Q4: Explain why the bulb would not glow in the arrangement shown in Fig. below:
Answer: The handle of the screw driver acts as an insulator. It does not allow current to flow and circuit is still open. Therefore the bulb does not glow in the arrangement.
Q5: Complete the drawing shown in Fig below to indicate where the free ends of the two wires
should be joined to make the bulb glow.
Answer: The bulb
will glow when circuit is complete i.e. one end of the wire from clip is
connected to positive terminal. Second end of the wire from the clip is
connected to the bulb.
Q6:
Would the bulb glow after completing the circuit shown in Fig. above (Q5) if
instead of safety pin we use an eraser?
Answer: No. An eraser is made of rubber which is a poor conductor of electricity. Therefore, bulb would not glow.
Q7:
What is the purpose of using an electric switch? Name some electrical gadgets
that have switches built into them.
Answer: An electric switch is a simple device which is used to break or complete an electric circuit. Switches are widely used in different electrical or electronic gadgets. A few are:
Answer: No.
Q9: Would the bulb glow in the circuit shown in Fig. below?
Answer: The electric bulb has two terminals, both the
wires are connected to the one terminal of the bulb. Current will not flow from
the bulb and it will not glow. To make glow, the two wires should be connected
to each terminal of the bulb, as shown below.
Q10:
What are the components of an electric circuit?
Answer: In general a circuit has the following components:
Q11: How many terminals are there in an electric cell?
Answer:An electric cell has two terminals; positive and negative. The metal cap is the positive terminal of the cell. The metal disc is the negative terminal.
Q12: Using the "conduction tester" on an object it was found that the bulb begins to
glow. Is that object a conductor or an insulator? Explain.
Answer:Since the object allows current to flow and completes the circuit. Due to this bulb begins to glow. It means the object is a conductor of electricity.
Q13: What are conductors? Give examples.
Answer: The materials which allow electric current to pass through them are called conductors.
Examples are: All metals (copper, silver, iron) are good conductors. Water usually contains impurities and traces of salt is also a good conductor. Human body is also a conductor.
Q14: What are insulators? Give examples.
Answer: Materials that do not allow electricity to pass through them are called insulators. Insulators oppose electric current and so they are used as protection from the dangerous effects of electricity.
Examples of insulators are glass, air, plastic, cotton, thermocol, wood and rubber.
Q15: Why should an
electrician use rubber gloves while repairing an electric switch at your home?
Explain
Answer: Electricians need to touch copper wires or they may accidentally come in contact with live wires (wires carrying current). Since human body is also a good conductor, electricians may get shock. Rubber is good insulator. To prevent themselves from electric shock or flow of current, the electricians use rubber gloves while repairing.
Q16: The handles of the tools like screwdrivers and pliers used by electricians for repair work usually have plastic or rubber covers on them. Can you explain why?
Answer: Without the help of insulators, the use of electrical tools like pliers and screwdrivers is impossible. Wood and plastics are insulators and help in avoiding direct contact with electric current. When electricians touch these live electric wires with the tools covered with plastic and wood, current does not flow in their body avoid any accident.
Q17(MCQ): In an electric bell, the electric energy is transformed into ____________energy.
(a)Mechanical energy
(b) Magnetic energy
(c) Sound energy
(d) Light energy
Answer: (b) Magnetic energy
Q18(MCQ): The tiny coiled metal wire present inside the bulb is called____________.
(a) Element
(b) Conductor
(c) Filament
(d) None of these
Answer: (c) Filament
Q19(MCQ): Which of the following is NOT a good conductor of electricity?
(a) Mercury
(b) Copper
(c) Plastic
(d) Aluminum foil
Answer: (c) Plastic
Q20(MCQ): Which of the following is a good conductor of electricity?
(a) Wood
(b) Paper
(c) Glass
(d) Graphite
Answer: (d) Graphite
Q21: What will happen if you join the two terminals of a cell without connecting them through a switch or a bulb?
Answer: By doing so, the chemicals in the electric cell get used up very fast and the cell will no longer produce electric current. It will stop working.
Q22: Why do an electric bulb and an electric cell have two terminals?
Answer: Because the two terminals (positive and negative) can be connected to form an electric circuit.
Q23: Is Distilled water a conductor of electricity?
Answer: No. The distilled water is the purest water and it acts as an insulator. Therefore, it used in batteries as an insulator. The tap water, sea water contains some traces of salts and impurities, due to which it becomes good conductor of electricity.
Q1. Fill in the blanks :(a) A device that is used to break an electric circuit is called _______________.
(b) An electric cell has _______________ terminals.
(c) Electric cell is a device which converts energy of chemicals into ________________energy.
(d) The electric energy which is supplied in our home comes from electric _______________houses.
(e) An electric ______________ is a continuous path along which the current flows.
(f) If the filament of a bulb breaks, it is said to be ______________.
(g) Rubber is a good example of electric ______________.
Answer:
(a) switch
(b) two terminals
(c) electrical
(d) poles nearby
(e) circuit
(f) fused
(g) insulator
Q2: Mark 'True' or 'False' for following statements:
Answer:
(a) Electric current can flow through metals. (✓ True)
(b) Instead of metal wires, a jute string can be used to make a circuit. (✗ False)
(c) Electric current can pass through a sheet of thermocol. (✗ False)
(d) When current flows through a circuit, the circuit is called open circuit. (✗ False)
(e) An electric bulb has one terminal (✗ False)
Answer: An electric cell is a device which converts chemical
energy into electric energy. It has two different metal plates:
- one is the positive terminal
- the other is the negative terminal
Q4: Explain why the bulb would not glow in the arrangement shown in Fig. below:
Answer: The handle of the screw driver acts as an insulator. It does not allow current to flow and circuit is still open. Therefore the bulb does not glow in the arrangement.
Q5: Complete the drawing shown in Fig below to indicate where the free ends of the two wires
should be joined to make the bulb glow.
Answer: No. An eraser is made of rubber which is a poor conductor of electricity. Therefore, bulb would not glow.
Answer: An electric switch is a simple device which is used to break or complete an electric circuit. Switches are widely used in different electrical or electronic gadgets. A few are:
- Toggle switches used in houses.
- Pushbutton switches used in microwaves, water pump, mixer etc.
- Joystick switches used in Video Games Controllers, Toy Cars etc.
Answer: No.
Q9: Would the bulb glow in the circuit shown in Fig. below?
Answer: In general a circuit has the following components:
- A cell or battery : source of electricity.
- Connecting wires
- Bulb or electric device
- Key or switch.
Q11: How many terminals are there in an electric cell?
Answer:An electric cell has two terminals; positive and negative. The metal cap is the positive terminal of the cell. The metal disc is the negative terminal.
Q12: Using the "conduction tester" on an object it was found that the bulb begins to
glow. Is that object a conductor or an insulator? Explain.
Answer:Since the object allows current to flow and completes the circuit. Due to this bulb begins to glow. It means the object is a conductor of electricity.
Q13: What are conductors? Give examples.
Answer: The materials which allow electric current to pass through them are called conductors.
Examples are: All metals (copper, silver, iron) are good conductors. Water usually contains impurities and traces of salt is also a good conductor. Human body is also a conductor.
Q14: What are insulators? Give examples.
Answer: Materials that do not allow electricity to pass through them are called insulators. Insulators oppose electric current and so they are used as protection from the dangerous effects of electricity.
Examples of insulators are glass, air, plastic, cotton, thermocol, wood and rubber.
Answer: Electricians need to touch copper wires or they may accidentally come in contact with live wires (wires carrying current). Since human body is also a good conductor, electricians may get shock. Rubber is good insulator. To prevent themselves from electric shock or flow of current, the electricians use rubber gloves while repairing.
Q16: The handles of the tools like screwdrivers and pliers used by electricians for repair work usually have plastic or rubber covers on them. Can you explain why?
Answer: Without the help of insulators, the use of electrical tools like pliers and screwdrivers is impossible. Wood and plastics are insulators and help in avoiding direct contact with electric current. When electricians touch these live electric wires with the tools covered with plastic and wood, current does not flow in their body avoid any accident.
Q17(MCQ): In an electric bell, the electric energy is transformed into ____________energy.
(a)Mechanical energy
(b) Magnetic energy
(c) Sound energy
(d) Light energy
Answer: (b) Magnetic energy
Q18(MCQ): The tiny coiled metal wire present inside the bulb is called____________.
(a) Element
(b) Conductor
(c) Filament
(d) None of these
Answer: (c) Filament
Q19(MCQ): Which of the following is NOT a good conductor of electricity?
(a) Mercury
(b) Copper
(c) Plastic
(d) Aluminum foil
Answer: (c) Plastic
Q20(MCQ): Which of the following is a good conductor of electricity?
(a) Wood
(b) Paper
(c) Glass
(d) Graphite
Answer: (d) Graphite
Q21: What will happen if you join the two terminals of a cell without connecting them through a switch or a bulb?
Answer: By doing so, the chemicals in the electric cell get used up very fast and the cell will no longer produce electric current. It will stop working.
Q22: Why do an electric bulb and an electric cell have two terminals?
Answer: Because the two terminals (positive and negative) can be connected to form an electric circuit.
Q23: Is Distilled water a conductor of electricity?
Answer: No. The distilled water is the purest water and it acts as an insulator. Therefore, it used in batteries as an insulator. The tap water, sea water contains some traces of salts and impurities, due to which it becomes good conductor of electricity.
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