STARS OF PIS AHMEDABAD STD VI

Thursday, February 24, 2022

SCIENCE CHAP 14. Air Around Us WORKBOOK QUESTION ANSWER

Objective type questions

14. Air Around Us

1. Choose the correct option.

a) The amount of nitrogen present in the atmosphere is __________. i) 20% ii) 78%

iii) 16% iv) 0.03%

ans: 78%

b) _________________ gas is used in extinguishing fires.

i) Oxygen ii) Hydrogen

iii) Carbon dioxide iv) Nitrogen

ans: Carbon dioxide

c) _____________ mark the beginning of the oxygen cycle. i) Bacteria ii) Land animals iii) Sea animals iv) Plants

ans: Plants

2. Name the following:

a) The excessive cutting of trees.

ans: Deforestation

b) The envelope of air surrounding the earth.

ans: Atmosphere

c) The method used for separation of husk from grains using wind. ans: Winnowing

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3. State whether the following statements are true or false.

a) Windmills are used to draw water from tube wells.

ans: True

b) The amount of water vapour present in the atmosphere is fixed. ans: False

c) Nitrogen supports combustion.

ans: False

4. Assertion-reasoning type questions:

In following questions, the Assertion and Reason have been put forward. Read the statements carefully and choose the correct alternative from the following: (A) Both Assertion and Reason are true and the Reason is a correct explanation of the Assertion.

(B) Both Assertion and Reason are true but Reason is not a correct explanation of the Assertion.

(D) Both Assertion and Reason are false.

a) Assertion: The ruler stoops to one side, when one of the balloons tied at the two ends of a ruler is punctured.

Reason: Air is invisible.

ans: (B) Both Assertion and Reason are true but Reason is not a correct explanation of the Assertion.

b) Assertion: Use of alternate sources of energy such as wind energy and solar energy should be encouraged.

Reason: Alternate sources of energy do not cause air pollution.

ans: (A) Both Assertion and Reason are true and the Reason is a correct explanation of the Assertion.

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Theory type questions

5. Define the following:

a) Oxygen cycle

ans: The cycle in nature in which the oxygen is consumed for respiration and is released during the process of photosynthesis is called oxygen cycle.

b) Air pollution

ans: The presence of undesirable substances in the air that cause harmful effects is known as air pollution.

6. Answer the following in brief.

a) What is the significance of hair and mucus present inside the nose of human beings?

ans: They prevent the dust particles from entering our lungs.

b) Which harmful gases are produced by burning of fuels in automobiles and factories?

ans: Harmful gases such as carbon monoxide, oxides of nitrogen and hydrogen sulphide produced by burning of fuels in automobiles and factories.

c) Give one use of nitrogen.

ans: It is used in the manufacture of fertilisers.

7. Give reasons for the following statements.

a) It is difficult to breathe at higher altitudes.

ans: As the layer of air is very thin at higher altitudes.

b) If a burning candle is covered using a tumbler, it goes off in sometime. ans: Oxygen is necessary for burning. The candle goes off as it uses up all

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the oxygen present inside the glass.

Picture based question

8. Observe the given picture and answer the questions that follow.

a) Why do you see bubbles escaping from the bottle?

ans: The bottle had air which escaped on tilting the bottle in the form of bubbles.

b) What can you conclude from the above activity?

ans: Air occupies space.

Real life learning

9. There is a chemical factory in your locality that emits lots of gases into the atmosphere. The harmful effects of this are seen on people living in nearby areas. Suggest any one step that the chemical factory can follow to reduce air pollution. ans: The chemical factory should install long chimneys so that the harmful gases are released high up in the air and away from humans.

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Fun based questions

10. Fill in the missing letters appropriately.

1. The process of formation of water vapour from water by heating. E V A P O R A T I O N

2. The harmful substances present in the air.

P O L L U T A N T S

HOTS

11. Higher Order Thinking Skills (HOTS)

What will happen if all plants were to vanish from the surface of the earth? Justify your answer.

ans: ∙ As the plants mark the beginning of the oxygen cycle, no plants means no photosynthesis.

∙ No photosynthesis means no oxygen for respiration and the very life on the earth will come to an end.

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Monday, February 7, 2022

SCIENCE CHAP 12 ELECTRICITY & CIRCUITS WORKBOOK QUES - ANSWER

Ch 12. Electricity and Circuits

1. Choose the correct option. (Ap/U)

a) Which of the following materials allow an electric current to pass through them?

i) Cotton ii) Copper

iii) Wood iv) Plastic

Ans: Copper

b) A dry cell consists of zinc metal that acts as the__________ terminal and a carbon rod that acts as the ___________ terminal of the cell.

i) negative, negative ii) positive, negative

iii) negative, positive iv) negative, negative Ans: negative, positive

c) _________ acts as the negative terminal of a bulb.

i) bottom of the bulb ii) Ammonium chloride iii) metal case iv) Manganese dioxide Ans: metal case

2. State true or false: (U)

a) Electricity is a form of energy resulting from the existence of charged particles.

Ans: True

b) We should use water to extinguish a fire in electric wires.

Ans: False

c) Electrons do not revolve around the nucleus in fixed orbits.

False

3. Give an example for each of the following. (Ap)

a) Natural resources used to generate electricity

Ans: Sun, wind, water and nuclear energy

b) Secondary cells

Ans: Car batteries

4. In the following questions, two statements are given- one labelled Assertion (A) and the other labelled Reason (R). Read the statements carefully and choose the correct alternative (A), (B), (C) and (D) as given below. (An)

(A) Both A and R are true and R is the correct explanation of the assertion. (B) Both A and R are true but R is not the correct explanation of the assertion.

(D) A is false but R is true.

a) Assertion : In an electric bulb, the filament is made up tungsten. Reason: Tungsten does not melt even when the filament glows at a very high temperature.

(A) Both A and R are true and R is the correct explanation of the assertion.

b) Assertion: If you notice a spark in a switch, put it off immediately with the help of a metal stick.

Reason: Metal is a good conductor of electricity.

(D) A is false but R is true.

5. Explain the following: (U)

a) Nucleus

Ans: Protons and neutrons form the central part of the atom called the nucleus.

b) Conductors

Ans: The materials that allow an electric current to flow through them.

6. Answer the following questions in brief. (R/U)

a) What is an electric cell? Name the two types of electric cells. Ans: Electric cell is a device that generates an electric current. It converts chemical energy into electrical energy. Electric cells are of various shapes and sizes.

Primary cell/dry cell and secondary cell/lead-acid accumulators

b) Name the scientist who has discovered electricity. Why is electricity important?

Ans: Benjamin Franklin

All gadgets and devices like computers, televisions, washing machines, refrigerators, fans, air conditioners, etc. which make our lives comfortable work on electricity.

7. State the function of each of the following: (R)

a) Electric switch

Ans: An electric switch is used to open or close an electric circuit.

b) The plastic coating of electric wires

Ans: Protect us from getting electric shocks.

8. You are given two dry cells, switch and bulb. Draw an electric torch showing two dry cells. Which component of the torch is responsible for the flow of electric current? (C)

Ans:

The electric cells inside the torch are responsible for the flow of electric current.

9. Observe the picture and answer the questions that follow. (Ap) (a) (b) (c)

In which of the following arrangements will the bulb? Give Reason. (b)

In (b), the bulb will glow as the circuit is complete.

10. Aditya performed an experiment to observe the flow of electric current through an electric bulb. The bulb is connected to the cells in two different ways as shown in (a) and (b). Which of these is the correct way to connect the bulb? Why? (U)

(a) (b)

(b) To complete the circuit and for the flow of current in the electric circuit, the arrangement of cells are in correct order.

11. Who am I ? (U)

1. I am displayed on electric poles and transformers, warning you to stay away from me.

Danger sign

2. I am a continuous flow of electrons

Electric current

3. I am round in shape. I provide energy to electronic devices like wrist watches and pocket calculators.

Button cell

12. Higher Order Thinking Skills (HOTS) (U)

Seema was testing electric circuits. She tested two conditions as given in fig A and fig B.

REFER TO TEXTBOOK FOR DRAWING

(a) What will be the direction of flow of current in fig A and fig B? fig A – P to Q

fig B – Q to P

(b) In which of the above figures will the bulb glow?

Both fig A and fig B

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SCIENCE CHAP ELECTRICITY & CIRCUITS TEXTUAL Q-ANS

Q5 Answer following questions in one word or one sentence.

a. What forms the negative terminal of a dry cell?

Answer:-The outer covering of a dry cell consists of zinc metal which acts as the negative terminal for the dry cell.

b. Give one example of a conductor.

Answer:- copper

c. What are insulators?

Answer:- The materials that do not allow any current to pass through them are called insulators.Eg:- Rubber,wood

d. In which direction does a current flow in a circuit ?

Answer:- Current flows in a circuit from positive terminal to negative terminal.

e. What is the central part of an atom made up of protons and neutrons called? Answer:- Nucleus.

Q6 Answer the following questions in short.

a. What is an electric circuit? State its components.

Answer :- The complete path through which an electric current flows is called an electric circuit.

An electric circuit consists of following components:

b. State the difference between conductors and insulators.

Answer:-

c. State the difference between open circuit and closed circuit?

Answer:-

d. Name the type of electric cells, State one difference between them. Answer:- There are two types of electric cell

1. Primary cell

2. Secondary cell

Difference between primary and secondary cell.

Primary Cell	Secondary Cell
Primary cells are batteries that cannot	Secondary cells are batteries that be

be recharged or reused	recharged or reused (known as lead acid accumulator)
Two types of dry cells are pencil cell and button cell	Car batteries are examples of secondary cells
Can be used only once	Can be used more than once

e. What is an electric current? list some source of electric current.

Answer:- An electric current is the flow of charge due to electrical energy. Sources of electric current

1. Coal, petroleum

2. Sun

3. Wind

4. Water

5. Nuclear energy

6. Oil

7. Gas

Q.7 Give reason:

a. wires have a plastic and rubber covering.

Answer:- Plastic and rubber are insulators which prevent current to flow from wire and protects us from electric shocks.

b. copper wire is used instead of wood in an electric circuit.

Answer:- copper wire is a good conductor of electricity and wood is an insulator. That is why copper wire is used in electric circuits.

c. It is advisable not to put our hands inside a plug socket.

Answer:- Our body is a good conductor of electric current and hence we can get an electric shock if we put our finger inside a plug a socket.

d. Tungsten is used as a filament in a bulb.

Answer:- Tungsten is used as a filament in a bulb because the melting point of tungsten is very high hence it does not melt even when the filament glows at a very high temperature.

Q.8 Answer the following questions in detail.

a. list out the safety measures that should be followed while handling electrical appliances. Answer :-

b. Explain the working of a bulb.

Answer:- The incandescent light bulb turns electricity into light by sending the electric current through a thin wire called a filament. Electrical filaments are made up mostly of tungsten metal. The resistance of the filament heats the bulb. Eventually the filament gets so hot that it glows, producing light.

c. Explain the structure of primary cell.

Answer :-

a. In picture ‘V’ the bulb will glow…..because wires are connect with correct terminals. b.

Answer:- a. the bulb will glow in set up ‘A’.

Because the l in set up ’ A’ the switch is on.

b. the ends of conducting wires are bare because those ends are required to be connected with battery and only conducting surface can flow current through them.