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Class 6 Science Physics

L – 10    MOTION AND MEASUREMENT DISTANCE

A       VERY SHORT ANSWER TYPE QUESTIONS:

Q1.         What do you mean by rest?

Ans.       If the position of a body does not change with respect to any fixed point in its surroundings, it is at rest or in a state of rest.

Q2.         What do you understand by motion?

Ans.       An object is in motion if its position changes with time in reference to a stationary object in the surroundings.

Q3.         Define linear motion and and give an example.

Ans.       Linear motion is that in which all the particles of a body move through the same distance in the same time. It is also called as translator motion. Eg. – 1. Motion of a drawer of a table. 2. A moving car or train.

Q4.         What is an oscillatory motion? Give an example.

Ans.       Oscillatory motion is that in which a body moves to and fro about its mean position.eg.- 1. The motion of a swing. 2. Pendulum of a clock.

Q6.         Name the SI unit of length.

Ans        Meter.

Q7.         What is meant by rectilinear motion.

Ans.       When a body moves a straight line, it is called rectilinear motion.

Q8.         Is it possible to measure the length of a curved line.

Ans.       Yes, it is possible to measure the length of a curved line using a cotton thread and metre scale.

Q10.       Give two examples each of modes of transport used on land, water and air.

Ans.       Two ex. Of transport:-   1. On land – car , bike, bus truck.               2. On water – motor boat, steamer, ship.             3. On air – aeroplane, helicopter.

Q5.         What do you mean by the length of an object?

Ans.       The length of an object is the distance measured from one end to another.

Q9.         The length of a person is 1.62 m express it in cm and mm.

Ans.       The height of a person = 1.62m

                The length of a person = 1.62 x 100 = 162 cm.

                The height of a person = 1.62 x 1000 = 1620mm.

B.            short ans. Type questions:

Q1.         distinguish between rest and motion.

Ans.       Rest – if the position of a body does not change with respect to any fixed point in its surroundings it is at rest or in a state of rest.

Motion - The continuous change of position of a body with respect to another is called motion.

Q2.         Define motion in detail and mention the common types of motion.

Ans.       The continuous change of position of a body with respect to another is called motion. Types os motion:-   1. Translator motion  2.   Rotator motion   3.   Oscillatory motion  4.  Periodic motion  5.  Repetitive motion.

Q3.         Distinguish between periodic motion and respective motion.

Ans.       Periodic motion is that which repeats itself after regular intervals of time. Eg.- the motion of the moon round the earth, the motion of a clock pendulum.

                Respective motion is that which occurs again and again eg. Moment of lips while speaking, flickering of eyelids.

C.            in which of the following measurements, length is being measured.?

Ans.       1.  Width  -  length, 2.  depth  - length,  3. Distance between Delhi and Agra  - length.  4.  Height  length   5.  Interval between departure of two buses  - time  6.  Distance moved by the car in one second – time  7.  Circumference -  length   8.            Change in position  -  length  9.  Change in position in time  - time.

B.            TICK THE ONLY CORRECT CHOICE :

Q1.         The motion of a drawer of a table is an example of          -              translator motion

Q2.         Periodic motio can be used to measure                                 -              time

Q3.         Air can move                                                                                      -              straight upwards, up, horizontally, in circles

Q4.         1/ 100 metre is equal to                                                                -              1 cm

Q5.         March past of soldiers in a parade is an example of          -              rectilinear motion

Q6.         Striker in the game of carom moves in a                                -              straight line

Q7.         Height of a person is 1.65m . its length in mm is                 -              1650

Q8.         Motion of potter’s wheel is                                                          -  circular as well as rotational

Q9.         Which is incorrect among the following?

Ans.       Motion a long curved path is called circular motion.

Q10.       Which of the following is a combination of rectilinear and rotational motion?

Ans.       A hard kick ball.

F.            GIVE ONE WORD ANSWER:

1.            Irregular motion of the body in which the direction is not fixed in  random motion.

2.            motion of surface of table being played – repetitive motion

3.            motion of fish in water because of its shape  - random motion.

4.            1 millenium = thousand years.

5.            place where standard units are measured in India  National Physical Laboratory

6.            distance of 2.6m is same as 2m 60cm.

7.            hands of a clock have periodic as well as oscillatory motion.

8.            All periodic motions could be repetitive motion.

9.            Oscillatory motion is periodic as well.

A             Complete the given analogy:

1.            1000mm : 1m : : 1m : 0.001 km

2.            Celsius : Kelvin : : g  : kg

3.            kg : quintal : : metre : kilometer

4.            1 micron : 10-6 m : : 1 angstorm : 10-10 m

5.            micron :  : : Angstorm : A0

B             PICK THE ODD ONE OUT.

1.            century                                                2.            Handful

C       Fill in the blanks:-

1.       A pendulum undergoes periodic motion.

2.       The motion of the earth around the sun is translator ( circular path) in nature.

3.       All periodic motions are repetitive but all repetitive motions are not periodic.

4.       Five kilometer is same as 5000.

5.       Motion of a child on a swing is oscillatory motion.

D.      MATCH THE COLUMN

1.            pendulum  -  oscillatory motion

2.            heartbeat  -  periodic motion

3.            potter’s wheel  -  rotator motion

4.            flickering of eyelids  -  repetitive motion

5.            ball rolling on the ground    -   Translatory and rotator motion

E.            WRITE  TRUE(T) OR FALSE  (F):

1.            repetitive motion is that which repeats itself after regular intervals of time. (F)

2.            the physical quantity that measures the distance traveled per unit time is called speed.(t)

3.            motion in a straight line is called rectilinear motion. (T)

4.            motion of the needle of a sewing machine is circular motion. (F)

5.            motion of wheel of a bycicle is rectilinear .(T)

6.            An object can have more than one type of motion. (T)

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C.1.        WHAT IS THE NEED FOR MEASUREMENT? WHAT ARE STANDARD UNITS AND WHY ARE THEY IMPORTANT?          

Ans.       Without making actual measurement we cannot make correct judgement. It is difficult to find out the length, area, volume by just looking at them. To make a reliable and actual judgement we need a standard measurement.

                The unit which is acceptable to the majority of the people as a basic unit of measurement is called a standard units.

                Scientists all over the world have accepted a basic set of units for the measurement of physical quantities and it is called as international system of units.

Q2.         What is the standard unit of length? What is the standard metre rod and where is it kept? In India, who is responsible for maintaining such standards?

Ans.       The standard unit of length is metre. A standard metre rod is used to measure lengths. It is marked or graduated in centimeters and millimeters. It is kept in the National Physical Laboratory at New Delhi. All the standard units are maintained by this National Physical Laboratory.

Q3.         How  can you measure the length of a curved line? Explain by drawing a suitable diagram.

Ans.       Take a white sheet of paper and draw a curved line on it. Also take 8 to 10 common pins and a thin and strong cotton thread. Now fix pins on the sharp turnings of the curved line. In the fig P, Q, R, S, T, and U are the pins. Tie a knot with cotton thread at P and move the thread along the curved line so that it goes around the pins Q, r,…,U etc. As you reach the extreme end of the curved line,  cut the thread from that point. Ensure that the thread is neither too tight nor too loose. Now remove the thread from P and place it straight along the length of a half metre scale. The length of the thread equals the length of the curved line.

Q4.         How will you measure the length of objects.

Ans.       Place the thread on the table. Place two wooden blocks such that both of these touch the thread and their lower edges  are along a metre scale. Measure the distance between the faces of the block.

Q5.         How can you measure the diameter of a cricket ball?

Ans.       Place a ball on the table place two wooden blocks such that both of these touch the ball and their lower edges are along a metre scale. Measure the distance between the faces of the block touching the ball.

Q6.         How will you measure the height of a person?

Ans.       The length of a person can be measured using a measuring tape. First, let the person stand behind a wall. Mark the height of the person by a pencil on the wall. Now you can measure the height from the marked point till bottom using a measuring tape. That is the height of a person.

B.            SHORT ANS. TYPE QUESTIONS:

Q4.         How  will you measure the length of an object using a measuring tape.

Ans.       When we are asked to measure the length of an object using a measuring tape then the zero mark on the tape is made to coinciding with the other end of the object is taken. In order to measure the length of the object more accurately, its length is measured. Along position of the tape and then the average of these measurement is taken. The reading so obtained gives the required length of the object.

Q5.         The distance between Radha’s home and her school is 3260m. express this distance in km.

Ans.       The distance in km is 3.260 km.

Q6.         Ans.       An elastic measuring tape is not used to measure the distance of its elongation property ( expanding and coming to normal) exact measurement cannot be made.

Q7.         Why are hand span and cubit not used as standard units ?

Ans.       Hand span and cubit are not used as standard units because it varies from person to person and it cannot be considered as a standard unit.

Q8.         Why can’t a footstep be used as a standard unit of length?

Ans.       Footstep of different person is different, so it cannot be considered as a standard unit of length.

Q9.         Arrange the following length in their decreasing magnitude:- 1 m, 1cm, 1km, 1mm.

Ans.       Ikm, 1m, 1cm, 1mm.

Q10.       The length of the needle is 30.4cm.

Activity 10.5

Q1.         To measure the thickness of a page of your notebook

Ans.       Count about 300 pages of your nootbook. With the help of a measuring scale, measuring the total thickness of  these pages. Divide the thickness by the total number of pages. The result gives the thickness of one page of your notebook.

Q2.         To measure the thickness of a fifty paise coin.

Ans.       Take about 20 fifty paisa coins and place them one upon the other. Measure the total thickness with a metre scale and then divide by the number of coins to get the thickness of one coin.

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L-13 FUN WITH MAGNETS

MAGNET :         a substance that possesses the property of attracting iron filings.

 POLES :              The two end of a magnet where its magnetic strength is maximum.

Magnetic field :               the region around a magnet where its influence can be felt.

Magnetic compass :   is a devise used for determining direction by means of a magnetic needle.

Fill in the blanks:

1.       Materials which are attracted by magnets are called magnetic substances.

2.       A magnet always comes to rest in the north-south direction when suspended freely.

3.       Poles

4.       Magnetism

5.       Attract

6.       Flat bars and U- shaped.

7.       Magnetic compass.

8.       The materials which get attracted towards the magnet are called magnetic material.

9.       Paper is not a magnetic material.

10.   Magnet poles always exist in pair.

ANSWER THE FOLLOWING IN ONE WORD:

1.       Not a magnetic material                -              zinc.

2.       Used to make a permanent magnet        -              steel.

3.       A magnet always has two poles it is called             -              dipole.

4.       Different  magnetic property      -              nickel

5.       A magnet does not lose its magnetism -                when it is kept in a magnetic field.

6.       Magnets attract                -              iron.

7.       In a magnet, magnetic domains are aligned in     -  all the direction.

8.       A magnet loosen its magnetic properties on heating because  -   magnet undergoes self – demagnetized.

9.       All natural magnets are  - week magnets

10.   Magnetic pole  -   always exist in pairs.

 

A.   VERY SHORT ANSWER TYPE QUESTIONS:   www.rsmaths99.com

 

Q1.         WHAT DO YOU MEAN BY A MAGNET?

Ans.       A substance that possesses the property of attracting iron fillings.

Q2.         What are natural magnet?

Ans.       Lodestone and magnetities are natural magnets because they are found in nature. Natural magnets have a low magnetic power.

Q3.         Name the two magnetic substances?

Ans.       Iron, cobalt nickel and their alloys are magnetic substances.

Q4.         What do you understand by the people of magnet?

Ans.       The two ends of a magnet where the magnetic force is maximum are called the poles of the magnet.

Q5.         What is the difference between a temporary and a permanent magnet.

Ans.      

Temporary magnet

Permanent magnet

Magnetic properties retained for only a short period of time.

Magnetic properties retained for longer of time.

It is made of iron, cobalt and nickel.

It is made from the mixture of iron, cobalt or nickel with other elements.

 

Q6.         What is the name of the naturally occurring magnet?

Ans.       Lodestone and magnetite  are examples of naturally occurring magnets.

Q7.         Is magnetic attraction maximum in the middle of a bar magnet?

Ans.       No magnetic attraction is not maximum in the middle of a bar magnet but it is in the poles.

Q8.         Yes, magnetic poles always exist in pairs.

Q9.         Opposite poles of a magnet attracts each other.

Q10.       Is it possible to use compass needle at poles?

Ans.       No, compass needle are not suppose to be used at poles. At poles the attraction will be vigorous. The needle keeps rotating in circle.

B.   SHORT ANSWER TYPE QUESTIONS:   www.rsmaths99.com

 

Q1.         Distinguish between natural and artificial magnets.

Ans.

 

Natural Magnet

Artificial Magnet

They are found in nature

It is prepared by man

They have low magnetic power

These magnets are much stronger.

They are found at very few places. Eg. Lodestone magnetites.

They are used at anytime and at any place. Eg. Bar magnet, U- shaped magnet.


 

Q2.         Write two important properties of artificial magnet.

Ans.       Two important properties of artificial magnets are :-

1.       Directional property – a magnet always point in the north- south direction when suspended freely.

2.       Like poles repel, unlike poles attract.

Q3.         Name any two devices in which magnets are used.

Ans.       Cell phone, cassettes.

Q4.         Which instrument uses a magnet to find directions?

Ans.       Magnetic compass is used to find directions.      

Q5.         A magnet has two poles. They are called North Pole and South Pole.

Q6.         What is a lodestone?

Ans.       Sailors used magnets to navigate their ships especially during cloudy weather. They gave it a Chinese  name meaning leading stone. This word gradually got changed to lodestone.

Q7.         Why do we need magnetic keepers?

Ans.       Magnets have a tendency to lose their magnetism if they are not properly taken care of. To keep them safe, they are kept in magnetic keepers.

Q8.         Under what conditions magnets looses their magnetic property?

Ans.       Magnets looses their magnetic property if  - heated to a very high temperature.

                By rough handling, droped forcefully on the floor,  hammered violently.

Q9.         How can you make a magnetic compass?

Ans.       Take a circular aluminum box at the base of which are marked directions like north, south, eas, west, north- east, north – west etc. from its centre, rises a sharp needle, over which is placed a magnetic needle. The magnetic needle is free to move in all directions. A circular glass plate is fixed on the top of the box. It points towards north – south direction.

C.    LONG ANSWER TYPE QUESTIONS:  www.rsmaths99.com

 

Q1.         What is a natural magnet? How can you tell whether a particular substance is magnetic or non – magnetic?

Ans.       Lodestone and magnetites are natural magnets because they are found in nature. Natural magnets have a low magnetic. We can tell a particular substance is a magnet when it is attracted towards a magnet otherwise it is not a magnetic substance.

Q2.        

Magnetic

Non- Magnetic

Iron, cobalt, soil, nickel.

Phosphorus, aluminum, plastic, paper, copper, silver, zinc, mercury water.

 

Q3.         The characteristic of a magnet are-  1.poles of a magnet  2. Directional property  3.  Like poles repel, unlike poles attract, 4.  Magnetic poles always exist in pairs.

                Poles of magnet  -  1.  North pole  2.  South pole

                Magnets are not isolated.

Q4.         Describe an activity to show the magnetic effects can pass through non- magnetic materials.

Ans.       Take a paper on which few iron fillings are placed. Now take a magnet, keep it under the paper and move in different directions. We will find the iron fillings upon the paper keeps on moving along with the magnet.

Q5.         Demonstrate an activity to show that repulsion is     test of magnetization.

Ans.       Take two bar magnets. Suspended one magnet with a piece of thread. It will come to rest in the north – south direction. Hold the other magnet in your hand and bring its north pole near the north pole of the suspended magnet. We will find that the north pole

Q6.         Five ways of  demagnetization are-

1.       Heated to the very high temperature. 2.  By rough handling. 3. Dropped forcefully on the floor.  4. Hammered violently.  5. When magnets are not stored using magnet keepers. 

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L – 11        LIGHT SHADOWS & REFLECTIONS

DEFINITATIONS:

TRANSPARENT OBJECT -  Substance which  allow light to pass through them easily and through which we can see easily are called transparent substances.

Translucent substances -  substances through which light can pass partially but we cannot see through them clearly are called translucent substances.

Opaque substances -  substances which do not allow light to pass through them at all are called opaque substances.

A.    MATCH THE FOLLOWING

 

1.       Pin hole camera        -              from real and inverted image of the object.

2.       Periscope                    -              is the device to see the object at higher level.

3.       Source of light           -              give out its own light.

4.       Luminuous object    -              are natural source of lights.

 

B.    TICK THE ODD ONE OUT AND GIVE REASON

 

1.       Sun, moon, jugnu, star.         Moon is non- luminous  object

2.       Mirror           -             we can see the picture through the mirror.

3.       Newspaper -              light cannot reflect through it.

 

C.     WRITE ONE WORD ANSWER  www.rsmaths99.com

 

1.       A substance that allows the light to pass through it -                transparent.

2.       A substance that fills the space between the opaque object and the screen shadow.

3.       A metal that absorbs least amount of the light incident on it -             translucent.

A.      Very short answer type questions:

Q1.         Is light a form of energy?

Ans.       Yes, light is a form of energy. Light excites the sense of vision in us.

Q2.         What is rectilinear propagation of light

Ans.       The property of light that it always travels in straight lines is called rectilinear propagation of light.

Q3.         What do you understand by a transparent medium?

Ans.       Substance which allow light to pass through them easily and through which we can see clearly are called transparent medium. Glass, water, air and cellphone paper are examples of transparent medium.

Q4.         What is meant by an opaque medium?

Ans.       Substances which do not allow light to pass through them at all are called opaque medium. Wood, metal, bricks and stones are examples of opaque medium.

Q5.         What is the difference between luminous and non- luminous bodies?

Ans.      

Luminous  bodies

Non –Luminous bodies

Substances which give out light of their own are called luminous bodies.

Substances which do not give out light of their own are called non- luminous bodies.

Eg.-sun, stars, a candle, oil lamp etc. gives us light.

Eg.- tables, chairs, books, trees, pens etc.

 

Q7.         State the principle of a pinhole camera?

Ans.       A pinhole camera is based upon the principle of rectilinear propagation of light. The property of light that it always travels in straight lines is called rectilinear propagation of light.

Q8.         What are mirrors? Give three important example.

Ans.       Mirror are highly polished surface from which regular reflection takes places. Eg.- plane mirror, concave mirror and convex mirror.

 

B.   SHORT ANSWER TYPE QUESTIONS  www.rsmaths99.com

 

Q1.         Distinguish between transparent and translucent bodies.

Transparent

Translucent

It allowes the light to pass through it easily.

It allows the light to pass through it partial

Eg. glass, water

Eg.  Butter paper, frosted glass.

 

Q2.         Give two example of extended source of light.

Ans.       Example of extended source of light are burning candle, a glowing electric bulb.

Q3.         Define translucent bodies? Give two eg.

Ans.       Substance which allows the light to pass partially and we cannot see through them clearly are called translucent bodies. Two examples are greased paper, wax paper.

Q4.         What do you mean by regular reflection?

Ans.       The type of reflection where, the reflected rays of light follows a uniform direction, is called regular reflection.

Q5.         What is the difference between image and shadow?

Ans.       An image is formed when the light is reflected from a mirror or any shining object. An image provides.

                A shadow is formed when the path of light is obstructed by an opaque body.

Q6.         We can create a shape that would give a circular shadow if held in one way and a rectangular shadow if held in another way is a cylinder.

FILL UPS

1.       Candles and gas lamp are example of man; made source of light.

2.       Sun is an example of luminous bodies.

3.       Glass is an example of transparent substances.

4.       The sun is 150 million km away from the earth.

5.       The object which emit light is called luminous body.

6.       Sun is an example of natural source of light.

7.       When an iron rod is heated to 600o to 800o centigrade temperature it becomes luminous body.

8.       The region of total darkness is umbra.

9.       Shadow of an object cannot be seen in dark.

10.   Reflection from mirror gives clear image.

11.   Neutral wire has black covering.

12.   Source of electricity is cell.

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L- 12 ELECTRICITY AND CIRCUITS    www.rsmaths99.com

A         solve the crossword puzzle.

Ans.       Top to bottom – SILVER, ANODE

                From left to right -  FILAMENT, KEY, CONDUCTOR

B.   ONE WORD ANSWER

Q1.         An insulator        -              wood.

Q2.         Good conductor of electricity     -              steel.

Q3.         If a current is drawn from the cell, the circuit is said to be -           complete.

Q4.         The closed path in which the current flows is called a/ an -    electric circuit.

Q5.         In a primary cell, the chemical change is converted into -               electrical energy.

Q6.         Dry cell.

Q7.         Key.

Q8.         Wood.

Q9.         Electric switch.

Q10.       Gas burner.

E        GIVE REASONS  www.rsmaths99.com

 

Q1.         Electric cell is said to be a source of electricity.

Ans.       A cell is able to produce electricity. So electric cell is said to be a source of electricity.

Q2.         The handle of the tools like screw drivers, and pliors used by electricians for repair work usually have plastic or rubber over on them.

Ans.       Plastic or rubber handles are used in screw drivers and pliers because they are insulators.

Q3.         Metals are used to produce electric wires.

Ans.       Metals are good conductors so they are used to produce electricity and the wires are used in it .

Q4.         Electric bulbs does not glow when cotton thread is used instead of metal wire.

Ans.       When cottonthread is used instead of metal wire, no current flows through it and bulb will not glow because cotton is not a conductors.

Q5.         Switches and electric sockets are made by using conductors.

Ans.       Because only through the conductor the current flows.

A.   VERY SHORT ANSWER TYPE QUESTIONS  www.rsmaths99.com

 

Q1.         What do you understand by a primary cell?

Ans.       Primary cells provide current as a result of the chemical reaction that takes place in the chemical stored in them. When the chemicals are used up, they stop producing electricity. They cannot be recharge.

Q2.         What do you mean by a battery?

Ans.       A combination of two or more electric cell is called a battery.

Q3.         What is the function of an electric bulb?

Ans.       An electric bulb is a device which changes electrical energy into light energy.

Q4.         Name the material that allows electric current to flow through it easily.

Ans.       The material that allows electric current to flow through it easily are silver, gold, copper, aluminum, iron etc.

Q5.         What is an electric curcit?

Ans.       Electric curcit is the closed path in which electric current flows.

Q6.         What is the common name of an electric switch?

Ans.       The common name of an electric switch is a key.

Q7.         What are terminals?

Ans.       The ends of an electric cell or any other electric device are known as terminals.

Q8.         Name the circuit component that is used to start or stop the flow of current in the circuit.

Ans.       Electric switch or a key.

Q9.         Will the electric current flow in a circuit in which there is a gap between two wires.

Ans.       No.

Q10.       Write the energy conservation of a dry cell.

Ans.       The energy conservation of a dry cell is that the chemical energy which is stored in a dry cell is converted to electrical energy.

 

B       SHORT ANSWER TYPE QUESTIONS  www.rsmaths99.com

 

Q1.         Distinguish between open and closed circuit.

Ans.       In a circuit if the wire is cut the flow of current is stopped and we  say that the circuit is open or incomplete. Thus in an open circuit no current is drawn from the cell. The flow of current is indicated by the glowing of an electric bulb included in the circuit. Thus, if a current is drawn from the cell, the circuit is said to be closed or complete.

Q2.         What is the difference between a cell and a battery?

Ans.       Cell – source of continuous supply of electric current.

                Battery -  a combination of two or more electric cell.

Q3.         Why should an electrician use rubber gloves while repairing an electric switch at your home.

Ans.       An electrician use rubber gloves while repairing an electric switch in order to avoid getting shocks.

Q4.         What is meant by conductors? Give two examples.

Ans.       Substances which allow electricity to flow through them are called conductors. Two examples are silver, gold, aluminum.

Q5.         What are insulators? Give two examples.

Ans.       Substance which do not allow electricity to flow through them are called insulators. Two eg. Are cotton, rubber.

Q6.         What is the source of electric switch?

Ans.       Primary cell, secondary cell, batteries, electric generator are the sources of electric current.

Q7.         What is the importance of electric switch?

Ans.       When the switch is ‘on ‘ , electric current is allow to flow through the circuit. On the other hand, if the switch is ‘off’ no  current flows through the circuit and the components of the circuit do not work at all. This is the importance of a switch.

Q8.         How are rechargeable cell different from ordinary dry cells?

Ans.       Rechargeable cells are electrically charged again and again and are used once and if its energy is over it is thrown away.

Q9.         Why can electricity not flow in an open circuit ?

Ans.       Electricity do not flow in an open circuit because there is a gap in the circuit, or the circuit is open.

 

C       LONG ANSWER TYPE QUESTIONS  www.rsmaths99.com

 

Q1.         Give the construction and working of a simple dry cell.

Ans.       A dry cell consists of a zinc casing and a carbon rod with a brass cap at its centre. The carbon rod is surrounded with a black powder. This black powder is surrounded by a thin layer of sawdust. A layer of pitch seals is used to prevent the leakage. The chemical reaction that takes  place in the cell produces electricity.

Q2.         Give the construction and working of an electric torch.

Ans.       The negative terminal of the cell presses  against the spring at the base of the torch. The positive terminal of the cell presses against the metal tip at the base of the bulb. There are three metal strips connected with the metal case the spring and part of a switch. When we press the switch circuit is complete. Then the current flows through the circuit and the bulb glows.

Q3.         Give the construction and working of an electric bulb.

Ans.       Electric bulb has a tiny coiled wire which is supported by two thick wires. This tiny coiled wire is called a filament. The lower end of one of the wire is joined to the metal casing. The lower end of the second wire is joined to the metal tip. The metal casing and the metal tip form the terminals of the bulb. On passing current through the terminals, the electric bulb produces light.

Q4.         What do you mean by an electric circuit? Draw the circuit for a circuit having three cells, one bulb and a switch.

Ans.       The closed path in which electric current flow is called an electric circuit.

Q5.         Distinguish between  www.rsmaths99.com

               

Conductors

Insulators

Substance which allow electricity to flow through them are called conductors.

Substances which do not allow electricity to flow through them are called insulators.

Eg. Silver, gold, aluminium

Eg. Cotton, rubber, plastic.

 

Q7.         Difference between;

               

Primary cell

Secondary cell

These cells provide current as a result of chemical reaction taking place. Which is irreversible.

It provide current due to chemical reaction taking place inside which is reversible.

It cannot be recharged.

It can be recharged.

Eg.- voltaic cell

Eg. – alkali accumulator

 

 B      GIVE ONE WORD ANSWER

1.       An electrical appliance which makes or brakes an electric circuit. Electric switch.

2.       The arrangement of providing a complete path for electricity to pass between two terminals of the electrical cell. Electric circuit.

3.       The combination in which two or more cells are joined to form a battery.

4.       Cells named accumulator. Lead accumulator.

5.       Chemicals used in dry cell MNO2 , C, NH4 Cl.

C       GIVE REASONS  www.rsmaths99.com

 

1.            Electric bulb does not glow even if it is connected to the cell?

                Ans.       Because the switch may be open/ off.

2.       Our body is good conductor of electricity.

Ans.       Because body contains liquid.

3.       A jute string cannot be used to make a circuit.

Ans.       Because jute is a bad conductor of electricity.

4.       Insulator is used to cover the wire

Ans.       Because insulators are not a conductor of electricity.

5.       Electrical gadgets  stop working . when switch is turned off.

Ans.       Because no current flows in an open circuit.

D       DO AS DIRECTED

1.            Instead of metal wires, a rubber string can be used to make a circuit. False

2.            Electric current can pass through a sheet of .  steel.

3.            cellophane paper does not allow electric current to pass through it.

4.            A switch is said to be off if the electric circuit is not complete.  True.

5.            Neutral wire has  black covering.

6.            current flows from the positive terminal of a cell through the circuit, to the negative terminal of the cell.  True.

7.            when two cells are joined to form battery, positive terminals of one cell should be connected to negative terminal of each other.

8.            the silver coloured reflector along with the bulb increases the intensity of torch light.  www.rsmaths99.com

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