821 + Interview Questions in Physics in Class 7

1.	Answer the following question Define melting and boiling points
Answer»

Discussion

2.	A whale swims due East for a distance of 5 km. turns around and goes due West for 1.8 km, and finally turns around again and heads 1.2 km due East. What is the distance and displacement of the whale?
Answer» SOLUTION :Distance 8 KM, displacement 4.4 km DUE EAST

Discussion

3.	The image formed by a plane mirror is at a distance behind the mirror as..........
Answer» SOLUTION :the OBJECT is in FRONT of it

Discussion

4.	How are dogs made alert by the crime department ? Explain.
Answer» Solution :Dogs can hear sounds of frequenciesgreaterthan 20 KHZ, which can not be heard by HUMAN beings. So, the crime department use galton WHISTLE to ALERT the dog by producing ultrasound waves which are heard by dogs.

Discussion

5.	{:("Column A","Column B"),(A."Pinhole camrea",(" ")a."Extended source"),(B."Kaleidoscope",(" ")b."Multiple reflecttion"),(C."Distance from pole to the center of a mirror",(" ")c."Rectilinear"),(D."Distance from the pole of the mirror to the principal focus.",(" ")d."Focal length"),(E."Tube light",(" ")e."Radius of curvature"):}
Answer» Solution :A-c Pin hole camera works on the PRINCIPLE of RECTILINEAR PROPAGATION. B-b KALEIDOSCOPE works on the principle of multiple reflection. C-e Distance between the pole of the mirror and center of curvature is called RADIUS of curvature. D-d Distance between the pole of the mirror and prinicpal focus is a called focal length. E-a A glowing tube light is an example of extended source of light.

Discussion

6.	Moon is a luminous object.
Answer» Solution :Moon REFLECTS the light which FALLS on it form the sun. So, MOONIS a non-luminous SOURCE (body).

Discussion

7.	______ are used to detect flaws inside a metal.
Answer» ANSWER :A::C::D

Discussion

8.	Answer the following question Give three examples each of a good and bad conductor of heat
Answer»

Discussion

9.	The time taken to perform 45 vibrations is ______ times the time taken for a single vibration.
Answer» ANSWER :D

Discussion

10.	A virtual image can be obtained on a screen.
Answer» SOLUTION :The IMAGE which cannot be caught on a screen is called VIRTUAL image.

Discussion

11.	The objects around us are seen due to irregular reflection of light.
Answer» ANSWER :T

Discussion

12.	Which of the following can be used as a measuring tool?
Answer» Hammer Divider Vice Hack-saw Solution :The DIVIDERS are USED for MEASUREMENTS

Discussion

13.	An object falling freely from the roof of a multistorey building has.............. and .......... energy when halfway down the building.
Answer» SOLUTION :POTENTIAL ENERGY and KINETIC

Discussion

14.	Describe the construction of calorimeter
Answer»

Discussion

15.	Six identical cells are connected as shown in the cir-cuit. The total e.m.f is "______"
Answer» 1.5 V 4.5 V 9 V 0 V Answer :B

Discussion

16.	The heating curve of a particular substance in solid state is a shown in the figure .choose the correct alternative The amount of heat energy absorbed by the substacne to change completely from liquid at its boiling point to gaseous state is _______J
Answer» 46185 2270 4538 4958 Solution :The substacne in LIQUID state CHANGE to gaseous state by absorbing energy of 2690 -420=2270 J

Discussion

17.	We should not touch the switch with wet hands, otherwise :
Answer» electricity may PASS through our body electricity may not pass through the appliance circuit may break the switch may GET off Solution :electricity may pass through our body

Discussion

18.	Which of the following tools hasa spring attached to it?
Answer» Hack-saw Vice Tin cutter Drilling tool Solution :A tin-cutter is similar to a pair of scissors, but a strong sering linking the handle of ONE BLADE and the BOTHER blade is FIXED

Discussion

19.	Match the entries given in Column A with the appropriate ones in Column B. {:("Column A","Column B"),(A."Air",(" ")a."Bioluminescence"),(B."Pure water",(" ")b."Opaque medium"),(C."Wood",(" ")c."Homogeneous"),(D."Glow warm",(" ")d."Heterogeneous medium"):}
Answer» ANSWER :A : D B : C C : B D : A

Discussion

20.	Define velocity and explain how it is different from speed.
Answer»

Discussion

21.	Heat capacity of 250 g of water is _________.
Answer» SOLUTION :Heat capacity C= m s C=250`xx` 1250 CAL `A^(@)C^(-1)`

Discussion

22.	The rear view mirrors used in vehicles are _____.
Answer» plane CONCAVE convex None of the above. Solution :The mirror which is USED as a REAR viewer in vehicles is a convex mirror.

Discussion

23.	Silver is an insulator of electricity.
Answer» ANSWER :FALSE

Discussion

24.	If the speed of an object is known, how can we find the distance coverd by it in a given time ?
Answer»

Discussion

25.	You have been given with a cup of coffee which is too hot to drink .Which among the following is the best method to cool it? Why? (i) Placing it in a beaker containing water (2) Placing it on the surface of wood (3) Placing it on the surface of an iron block
Answer» SOLUTION :The best method to cool it is to place it in water .The HEAT tranfer rate with wood is less compared to the iron block but when it placed on an iron block only the bottom surface is in conatact with the iron block but whne it is placed in a beaker CONTAINING water the heat transfer rate is also more hence the COOLING effect is more when it is placed in water

Discussion

26.	The _________toos should be be cleaned the and oilded after every use
Answer» ANSWER :METAL

Discussion

27.	Electromagnets are made up of:
Answer» steel copper brass SOFT IRON Solution :soft iron

Discussion

28.	"_______" acts as a positive pole and "_______" as a negative pole in a dry cell.
Answer» ANSWER :CARBON ROD, ZINC can

Discussion

29.	Define acceleration and state its SI unit.
Answer»

Discussion

30.	..................... pass electricity through them.
Answer» SOLUTION :CONDUCTORS

Discussion

31.	Kerosene contracts on heating.Given statement is true orfalse?
Answer» ANSWER :F

Discussion

32.	The light rays from a point object placed at the focus of a concave mirror, after reflection
Answer» emerge perpendicular to the PRINCIPAL axis. emerge parallel to the principal axis. form REAL image. Both (b) and (c) Solution :When LIGHT RAYS pass through the FOCUS of a concave mirror, the reflected rays emerge parallel to the principal axis.

Discussion

33.	Heat lost by radiationdepends upon whether the outer surface of body is black or polised
Answer» Solution :Heat transfer by RADIATION DEPENDS upon whehterthe outer surface of the body is BLACK or POLISHED

Discussion

34.	A ray of light is incident on a plane mirror, making an angle 'q' with the surface of the mirror. Arrange the following steps in sequential order to calculate the angle betweenthe incident light ray and the reflected light ray. (A) Draw a normal line on the plane mirror at the point of incidence of the light ray. (B) Note down the angle between the plane mirror and the incident light ray. (C) The sum of the angle of incidence and the angle between the plane mirror and the incident ray is 90^(@).Determine the angle of incidence. (D) From the laws of reflection, the angle of incidence is equal to the angle of reflection. Then the sum of the angle of incidence and the angle of reflection gives the angle between the incident light ray and the reflected light ray.
Answer» DACB CDAB BACD DBAC Solution :Note down the given angle, i.e., the angle between the incident light RAY and the plane MIRROR. Draw a normal line on the plane mirror at the POINT of incidence. The sum of the angle between the normal and the incident light ray and the angle between the plane mirror an the incident light ray is `90^(@)`. From this, determine the angle ofincidence is EQUAL to the angle of REFLECTION. Then the sum of the angle of incidence and the angle of reflection gives the angle between the incident light ray and the reflected light ray.

Discussion

35.	Which of the following tools does not have any jaws on it ?
Answer» TINCUTTER MULTIPURPOSE TOOL HACK saw Vice Answer :C

Discussion

36.	A block is 8 cm long, 2 cm wide, and 3 cm high and has a mass 375 g. Express density in kg//m^(3)
Answer» SOLUTION :`7.8 XX 1,000 = 7,800 kg//m^(3)`

Discussion

37.	SHORT CIRCUITING
Answer» Solution :Connecting MANY DEVICES to a single socket leads to overload in the CIRCUIT.

Discussion

38.	The heat energy produced by the complete combustion of 25 g of a fuel is supplied to 500 g of water to increase the value of temperature from 35^(@)C to 55^(@)C .Find the calorific value of thefuel (specific heat capacity of water =1 cal g^(-1)^.@C^(-1))
Answer»

Discussion

39.	Convert 40^@C to the fahrenheit scale
Answer» SOLUTION :`104^@F`

Discussion

40.	A concave mirror is formed from a sphere of radius 20 cm. The image of an object at an infinite distance is formed at a distance of _____ cm from the mirror.
Answer» Solution :When the object is placed at infinite distance, the image is formedat the PRINCIPAL focus. RADIUS of CURVATURE, (R) =20 cm. Focal length `-(R)/(2)=(20)/(2)=-10cm`.

Discussion

41.	Sound is produced when a body............
Answer» SOLUTION :VIBRATES

Discussion

42.	A car moving on a straight road is an example of:
Answer» ROTATORY motion rectilinear motion oscillatory motion periodic motion Answer :B

Discussion

43.	Match the entries given in column A with the appropritate ones in column B
Answer» Solution :A-dThermometric liquid shouldexert a very vapour pressure B-e FREEZING point of water is marked as lower fixing point on the theremometer C-b Because of ANOMALOUS behavious of water auatic life can EXIST at the bottom even the top surface ofthe ponds FREEZE D-f MAXIMUM temperature on the Mercury is about `240^(@)C` F-c Normal human body temperature is `37^(@)C =273+37=310 K`

Discussion

44.	A ball falls down vertically. Its motion is :
Answer» PERIODIC linear circular VIBRATORY ANSWER :B

Discussion

45.	If a bus travels a distance of 30 km in 45 minutes. What will be its speed in: km//"s "
Answer» SOLUTION :45 minutes = 45 xx 60 SECONDS = 2700 s speed in `km//s 30 //2700= 0.011km//s`

Discussion

46.	Akbarobserved that the things placed inside the refrigerator become cold. He wanted to know how does the ehat flow from the inside of the refrigerator to the ouside of the refrigerator .Explain
Answer» Solution :In a refrigeratro the refrigerant (the LIQUID used for refrigeration) is in the liquid STTE and is EVAPORATED suddenly because of this there is a reduction in temperature and it is used to REMOVE the temperature inside the refrigerator

Discussion

47.	A metallic rod is bent in the form of ractangle as shown in the given figure and heated .Then the gap between the ends P and Q ______
Answer» INCREASES decreases remains same CONNOT be determined Solution :When the ROD is heated the distacne between any adjacent molecules increases hence the perimeter of rectangle and the gap between P and Q increases

Discussion

48.	Liquids are heated by conduction and radiation.
Answer» ANSWER :F

Discussion

49.	The flash of lightening is seen much before we hear the thunder because
Answer» the SPEED of LIGHT is more than the speed of sound. the speed of sound is more than the speed of light. the speed of light is EQUAL to the speed of sound. the speed of sound is more in VACUUM than in air. Solution :The lightning is seen much before we HEAR the thunder because the speed of light is more than the speed of the sound in a given medium.

Discussion

50.	A body can be charged by
Answer» FRICTION INDUCTION CONDUCTION All the above. Solution :A BODY can be CHARGED by friction, conduction and induction.

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

Answer the following question Define melting and boiling points

A whale swims due East for a distance of 5 km. turns around and goes due West for 1.8 km, and finally turns around again and heads 1.2 km due East. What is the distance and displacement of the whale?

The image formed by a plane mirror is at a distance behind the mirror as..........

How are dogs made alert by the crime department ? Explain.

Moon is a luminous object.

______ are used to detect flaws inside a metal.

Answer the following question Give three examples each of a good and bad conductor of heat

The time taken to perform 45 vibrations is ______ times the time taken for a single vibration.

A virtual image can be obtained on a screen.

The objects around us are seen due to irregular reflection of light.

Which of the following can be used as a measuring tool?

An object falling freely from the roof of a multistorey building has.............. and .......... energy when halfway down the building.

Describe the construction of calorimeter

Six identical cells are connected as shown in the cir-cuit. The total e.m.f is "______"

The heating curve of a particular substance in solid state is a shown in the figure .choose the correct alternative The amount of heat energy absorbed by the substacne to change completely from liquid at its boiling point to gaseous state is _______J

We should not touch the switch with wet hands, otherwise :

Which of the following tools hasa spring attached to it?

Match the entries given in Column A with the appropriate ones in Column B. {:("Column A","Column B"),(A."Air",(" ")a."Bioluminescence"),(B."Pure water",(" ")b."Opaque medium"),(C."Wood",(" ")c."Homogeneous"),(D."Glow warm",(" ")d."Heterogeneous medium"):}

Define velocity and explain how it is different from speed.

Heat capacity of 250 g of water is _________.

The rear view mirrors used in vehicles are _____.

Silver is an insulator of electricity.

If the speed of an object is known, how can we find the distance coverd by it in a given time ?

You have been given with a cup of coffee which is too hot to drink .Which among the following is the best method to cool it? Why? (i) Placing it in a beaker containing water (2) Placing it on the surface of wood (3) Placing it on the surface of an iron block

The _________toos should be be cleaned the and oilded after every use

Electromagnets are made up of:

"_______" acts as a positive pole and "_______" as a negative pole in a dry cell.

Define acceleration and state its SI unit.

..................... pass electricity through them.

Kerosene contracts on heating.Given statement is true orfalse?

The light rays from a point object placed at the focus of a concave mirror, after reflection

Heat lost by radiationdepends upon whether the outer surface of body is black or polised

Which of the following tools does not have any jaws on it ?

A block is 8 cm long, 2 cm wide, and 3 cm high and has a mass 375 g. Express density in kg//m^(3)

SHORT CIRCUITING

The heat energy produced by the complete combustion of 25 g of a fuel is supplied to 500 g of water to increase the value of temperature from 35^(@)C to 55^(@)C .Find the calorific value of thefuel (specific heat capacity of water =1 cal g^(-1)^.@C^(-1))

Convert 40^@C to the fahrenheit scale

A concave mirror is formed from a sphere of radius 20 cm. The image of an object at an infinite distance is formed at a distance of _____ cm from the mirror.

Sound is produced when a body............

A car moving on a straight road is an example of:

Match the entries given in column A with the appropritate ones in column B

A ball falls down vertically. Its motion is :

If a bus travels a distance of 30 km in 45 minutes. What will be its speed in: km//"s "

Akbarobserved that the things placed inside the refrigerator become cold. He wanted to know how does the ehat flow from the inside of the refrigerator to the ouside of the refrigerator .Explain

A metallic rod is bent in the form of ractangle as shown in the given figure and heated .Then the gap between the ends P and Q ______

Liquids are heated by conduction and radiation.

The flash of lightening is seen much before we hear the thunder because

A body can be charged by

"_" acts as a positive pole and "_" as a negative pole in a dry cell.