Electric Currents and Circuit

A. Fill in the blanks.

1. The thin coiled wire, that gives light, when heated up, is known as the ___________ of
an electric bulb.
2. An electrical device needs at least ___________ terminals.

3. An electric bulb glows when a ___________ flows through it.

4. The device, that is used to ‘break’ or ‘make’ an electric circuit, is called an

___________.

5. The materials, which (easily) let electricity flow through them, are called ___________.

6. Electric current ___________ pass through a sheet of plastic.

Answer: (1) filament (2) two (3) current (4) electric switch (5) conductors (6) does not

B. Write True or False for the following statements.

1. A dry cell stops working when the chemicals in it get used up.

2. Electric current is taken to flow from the negative terminal of the (electric) cell to the
positive terminal of the cell.

3. We need to complete the relevant electric circuit to enable an electric device to work.

4. Button cells are used in wrist watches.

5. We can use a polyester thread, in place of metal wires, to complete an electrical circuit.

Answer: (1) True (2) False (3) True (4) True (5) False

C. Tick the correct option.

Answer:
(1) filament
(2) filament gets heated up and then starts emitting light.
(3) a source of electric current, a few conducting wires as well as an electric switch.
(4) both switches 1 and 2 are in their ‘ON’ positions.
(5) option B.

D. Answer the following questions in brief.

1. State the function of the metallic strips used in a torch?

Answer: Metallic strips act as the conducting wires through which electricity flows when
switch is in ‘ON’ position.

2. The given diagram shows a dry cell with its different parts marked as 1, 2, 3, 4 and 5.
Which of them are the ‘two terminals’ of the dry cell?

Answer: The two terminals are:

• 1-metal cap (positive)

• 5-Zinc case (negative)
3. Write the meaning of the term ‘electric circuit’?

Answer: A complete and closed path through which an electric current can flow is known
as an electric circuit.

4. State the role of an electric switch in an electric circuit.

Answer: Electric switch helps us to start and stop the flow of current as and when
required.

5. Tools, like screw drivers and pliers, used by electricians, have handles made up of, (or
covered with) plastic, rubber or wood. Why?

Answer: Plastic, rubber or wood are good insulators and do not allow electricity to pass
through them and thus prevent electricians from electric shock.

6. Why should we always dry our hands before touching an electric appliance, or a
switch?
Answer: We should always dry our hands before touching an electrical appliance or a
switch because ordinary water is a reasonably good conductor of electricity and thus, we
may get an. electric shock leading to serious injuries.

E. Answer the following questions.

1. Write in brief, the working of an electric torch.

Answer: When we slide/press the switch of an electric torch, electricity starts flowing from
the electric cells to the electric bulb. This flow of electric current heats up the filament of
the bulb. The bulb, therefore, lights up.

2. A student, while performing an experiment in the science laboratory, connected an

electric bulb to an electric cell through an electric switch. He noticed that the bulb did not
glow when the electric switch was set in its ON position. Mention ‘any two reasons for this
observation.

Answer: Two possible reasons for this observation are: –

1. Connections may be loose or unclear.

2. Cell may not be working. Or The bulb may be fused.

3. Separate out the devices, listed below, into categories that usually work with (i) either
batteries or mains (ii) batteries only (iii) mains only.

kettle, iron press, calculator, toaster, mobile phone, washing machine, radio, transistor,
computer, microwave oven.

Answer:

Either batteries or mains: Computer

Batteries only: Calculator, mobile phone, radio, transistor

Mains only: Kettle, iron press, toaster, Microwave oven, washing machine.

4. Match the labels to the correct parts of the circuit given below. Will this circuit work?
Justify your answer.
Answer: No, this circuit will not work because switch is in its off position.

5. Distinguish between the term’s conductors and insulators of electricity. Give two
examples of each type.

Answer:

Conductors: Materials, which allow electricity to pass through them easily, are called
conductors.

Examples – silver, copper.

Insulators: Materials, which do not allow electricity to pass through them, are called
Insulators.

Examples-rubber, plastic.

Light and Shadows

A. Fill in the blanks.

1. An object that allows light to pass through it (almost) completely, is known as a

___________ object.

2. A shadow is observed, on a screen, when an ___________ object comes in, between it

and a source of light.

3. Shadows formed are always ___________ irrespective of the colour of the object.

4. A ___________ is a natural phenomenon that sometimes occurs on a new moon day.

5. When light is reflected from a plane mirror, it changes its ___________ of propagation.

Answer: (1) transparent (2) opaque (3) black (4) Lunar eclipse (5) direction

B. Match the following:

 Match the following
Answer: (1) e, (2) d, (3) a, (4) c, (5) b

C. Tick the correct option.

1. Objects, like the sun, which emit light of their own, are called

Answer: luminous objects

2. An object, through which we can see partially, but not very clearly, is

Answer: a sheet of tracing paper

3. The ‘something’, which can change its shape and size, and may appear and disappear
anywhere/anytime, is known as a-

Answer: shadow

4. When sun (during early morning) is behind an object, the size of its shadow in
comparison to that of the object would be

Answer: larger

5. The image, formed by a pinhole camera, is

Answer: inverted and diminished

D. Answers the following questions in brief.

1. Classify the materials given below as opaque, transparent or translucent.

air, smoke, fog, aluminum sheet, wooden board, cello tape, polythene sheet, lime juice,
wax, rubber, Tyre and milk

Answer:

Opaque materials – aluminum sheet, wooden board, rubber, tyre and milk.

Transparent materials – air, cello tape, Polythene sheet, lime juice.

Translucent materials – smoke, fog, wax.

2. State the type of path that light ordinarily follows when going from one point to
another?

Answer: straight line

3. Do fishes cast shadows in water?

Answer: Yes, fishes cast shadows in water because the body of a fish is opaque. Hence if
sunlight falls on it, shadow will form on the other side. But it depends on how far is the
screen from the fish.

4. On a sunny day, two identical bedsheets, of red and green color, are hanging on a
clothes line. What would be the color of the shadows of these two bed sheets?

Answer: Shadow will form black in color. It is so because the color of shadow does not
depend on the color of the object.

5. State the relative positions, of the sun, moon and the earth, during a lunar eclipse.

Answer: During the lunar eclipse the earth comes in between the sun and the moon in a
straight line.

E. Answer the following questions.

1. Cover the face of a torch with a transparent coloured paper. Send its beam through an
opaque object. What do you observe?
Answer: When we Cover the face of a torch with a transparent coloured paper and send its
beam through an opaque object. Then we observe that a shadow is formed in black colour.
It means that the colour of the shadow does not depend on the colour of the light.

2. With the help of suitable diagrams, show that the size of shadow formed, depends upon
the relative position of the source and the opaque object.

Answer: Send a beam of light from the powerful torch over a circular piece of cardboard
to obtain its shadow on the screen (opposite wall).

Diagram (a) and (b)

Now move the Cardboard piece towards the torch piece. We observe that the shadow has
become larger in its size as compared to the first case.

3. Raghav set up the following arrangement in the science laboratory. He put (i) a steel
glass (ii) a transparent glass, at the position P. one by one. Would a shadow be formed in
each case? Give reason for your answer.

Answer:

(i) In this case shadow will form because a steel glass is an opaque material.

(ii) In this case shadow will not form because a transparent glass is kept at P.

4. With the help of a diagram, show the formation of an image by a pinhole camera.

Answer:

formation of an image by a pinhole camera

5. Give the meaning of the term ‘Lateral inversion. Suggest how it may be used to send a
‘coded (secret)’ message.

Answer: When we raise our right hand in front of a plane mirror, our image appears to
raise its left hand and vice-versa. This property is called lateral inversion.

The ambulance vans needed medical emergencies make use of the phenomenon of lateral
inversion. The word AMBULANCE is written in lateral inversion on their front side. The
driver of a car going ahead of this vehicle sees it as AMBULANCE and therefore gives the
right way to such vehicles.

Magnets

A. Fill in the blanks.

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

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

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

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

5. Magnets have been used for ___________ purposes.

Answer: (1) Non-magnetic materials (2) permanent (3) Magnetic poles (4) north poles (5)
different

B. Write True or False for the following statements.

1. Naturally occurring magnets are called loadstones.

2. An aluminum foil would get attracted by a magnet.

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

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

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

Answer: (1) True (2) False (3) True (4) False (5) False

C. Tick the correct option.

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

Answer: loadstone

2. A magnet can attract-

Answer: an iron nail

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

Answer: soft iron

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

Answer: north-south direction

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

Answer: a geyser

D. Answers the following questions in brief.

1. State any two properties of a bar magnet.

Answer: Two properties of a bar magnet are-

1. Attractive property: – the magnet is capable of attracting a small piece of iron, steel, etc.

2. Directive property: – a freely suspended magnet always points along the north and
south direction.
2. Maximum iron filling stick to the two ends of a bar magnet. Why?

Answer: Maximum iron filling stick to the ends of a bar magnet because strength of a bar
magnet is maximum near the poles.

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?

Answer: we observe repulsion, when we bring the north pole of one bar magnet towards
the north pole of another freely suspended bar magnet.

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

Answer: Magnet X floats above magnet Y, because of the two magnets X and Y are having
same poles towards each other.

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

Answer: We can make the steel needle into a magnet by placing it near a bar magnet for
some time, this is because the needle acquires some magnetism.

E. Answer the following questions.

1. Distinguish between the following:

(a) permanent magnets and temporary magnets.

Permanent magnets Temporary magnets

These are magnets that once made
These are magnets that once made remain as
remain as a magnet only for a short
magnets for a long period of time.
interval of time.
Steel, cobalt steel, alnico and ticanol are some Soft iron and nickel are two of the
of the materials that are used for making materials used for making temporary
permanent magnets magnets.
(b) magnetic and non-magnetic materials.

Magnetic materials Non magnetic materials

 Materials which get attracted towards a Materials that do not get attracted towards a
magnet are called magnetic materials. magnet are called non magnetic materials.
Examples: Iron, Steel, cobalt, nickel etc. Examples: Paper, wood, straws etc.
2. Two bar magnets, ‘P’ and ‘Q’ are kept as shown in the following diagram.

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

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

Answer: (a) point ‘a’ represents the north pole of magnet P.

Answer: (b) attraction will happen when the end ‘d’, of magnet ‘Q’ is brought towards the
end ‘b’ of magnet ‘P’.

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

Answer: 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 mark on it.

It is used to locate the north and south direction at a place.

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’.

Answer: diagram to show the proper way of storing two bar magnets’, when they are not
in use

labelled diagram
Advantages of proper storing of bar magnets is- Bar magnets do not lose their magnetism
for long period of time.

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

Answer: Different ways through which magnets can be made to lose their magnetism are –

• Magnets lose their magnetic properties when heated or mishandled

(dropped/hammered).
• If magnets are not stored properly their strength keeps on decreasing with time.
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.

Answer: she must have done this with the help of a strong magnet which can attract the
steel clips located at the bottom of a very shallow puddle of water.

Fabric from Fibre

A. Fill in the blanks.

1. Cotton plants grow well in ___________ soil.

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

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

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

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

Answer: (1) black (2) fruit, bolls (3) fleece (4) sheep, goat, camel (5) bark

B. Match the following:

 Match the following
Answer: (1) c, (2) d, (3) a, (4) e, (5) b

C. Tick the correct option.

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

Answer: linen

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

Answer: cotton-seeds

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

Answer: spinning

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

Answer: looms

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

Answer: alluvial, and black, soils

D. Answers the following questions in brief.

1. How are clothes important for us?

Answer: Cloth help us to cover our body and protects us from unfavorable climatic
conditions.
2. Define the term ‘natural fibres.

Answer: The fibres which are obtained from nature like from animals, plants, etc., is
called natural fibres.

3. Give two examples of plants fibres.

Answer: Cotton and Jute.

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

Answer: Alluvial soil.

5. Where is coir obtained from?

Answer: 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.

Answer: Cotton plants grow well in black soil. Warm and humid climates having
temperature of over 16 degrees C, provide the most suitable conditions for the growth of
cotton plant.

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

Answer: Jute plant uses up the fertility of the soil to a large extent. Therefore, fresh soil is
needed every year for the cultivation of jute plants.

Three uses of jute

• It is used for making funny bags.

• Use in making ropes.
• It is also used for making carpets & mats.
3. Give the difference between ‘spinning’ and ‘weaving’.
Answer: Spinning is the process of twisting the raw fibres together to make yarn. While,
weaving is the process of making clothes from yarn.

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

Answer: The complete process of making cloth, from its raw material, involves various
steps. These steps are given below, in the sequence in which they are carried out.

Chapter 14 Class
6
5. Differentiate between natural and synthetic fibres. State any three advantages of
synthetic fibres over natural fibres.

Answer: Natural fibres obtained from natural sources like plants and animals. While,
synthetic fibres made from chemicals that are prepared in factories.

The three advantages of synthetic fibres over natural fibres are:

a) They are wrinkle free. b) They have fast colour. c) They are not spoiled by moths.