821 + Interview Questions in Physics in Class 7

1.	The velocity of sound is ____ in air compared to that of water.
Answer»

Discussion

2.	The density of water at 4^@C is:
Answer» 1 g `cm^(-3)` 100 KG `m^(-3)` 1000 g `cm^(-3)` 1 kg `m^(-3)` Solution :Density of WATER at `4^(@)C` is 1 g `cm^(-3)`.

Discussion

3.	One millisecond is _____part of a second.
Answer» ANSWER :`1/1000`

Discussion

4.	Which of the following tools can be used to cut the metal plates of smallest thickness?
Answer» Tic cutter Scissors Piler Hack-saw Solution :Tincutter is the tool which is used to CUT the METAL plates of SMALLER thickness

Discussion

5.	Periscope works on the pirnciple of ______ of light.
Answer» ANSWER :REFLECTION

Discussion

6.	The sky appears blue due to scattering of light.
Answer» SOLUTION :As LIGHT scatters most, the SKY appears BLUE.

Discussion

7.	Sun light is not necessary for the growth of plants.
Answer» Solution :Photosynthesis TAKES PLACE in the PRESENCE of SUN light.

Discussion

8.	A piece of steel has a volume of 10 cm^(3) and a mass of 80 g. What is its density in: kg//m^(3)
Answer» Solution :To convert `1g//cm^(3)` to `kg//m^(3)` we have to multiply by 1000 HENCE `8g//cm^(3)= 8 XX 1000= 8000 kg//m^(3)`

Discussion

9.	Which of the following tools can be fixd in the colletof a multipurpose tool the drill holes in to a wooden plank?
Answer» SOLUTION :We can make HOLES in wooden planks by FIXING a DRILL bit in the multipurpose tool

Discussion

10.	Explain why, a ray of light passing through the centre of curvature of a convace mirror gets reflected back along the same path.
Answer» passes through the principal focus RETRACES its PATH passes ALONG the principal focus NONE of these Solution :An inicdsent ray passing through the CENTRE of curvature retraces its path.

Discussion

11.	Convert 10^@C in kelvin
Answer» SOLUTION :`t^@C` = (273 + t) K `10^@C` = (273 + 10) K = 283 K

Discussion

12.	All solids expand by the same amount when heated to the same rise in temperature.
Answer» ANSWER :F

Discussion

13.	Assertion (A): Convex mirrors are used as rear view mirrors in vehicles. Reason:(R) : The field ivew of convex mirror is maximum and they form diminished images.
Answer» Both A and R are correctand R is the corrcet EXPLANATION of A. Both A and R are CORRECT but R is not the correct explanation of A. A is correct and R is incorrect. Both A and R are incorrect. Solution :Convex mirror are used as rear view mirror in vehicles because the field view of a convex mirror is LARGE and it forms a DIMINISHED image so that the vehicles COMING from behind can be observed. So, A and R are correct, and R is the correct explanation of A.

Discussion

14.	{:(,"Column A",,, "Column B"),(A., "Frequency", (), a., "Detect flaws inside a metal"),(B., "The loudness of sound", ( ), b., "Ghatam"),(C., "The angle of incidence", ( ), c., "Equal to the angle of reflection of sound"),(D., "Ultrasounds", ( ), d., "Amplitude"),(E., "Ghana vadya", (), e., "Ratio of the number of oscillations to the time taken"):}
Answer» `A to e, B to d, C to c, D to a, E to b` `A to c, B to e, C to b, D to a, E to d` `A to d, B to c, C to e, D to d, E to a` `A to e, B to c, C to d, D to a, E to b` Solution :`{:(A - c,, "frequency " = ("Number of OSCILLATIONS")/("Time taken")),(B - d,, "The loudness of SOUND depends upons the amplitude of vibrations."),(C - c,, "The angle of incidence is equal to the angle of reflection of the sound."),(D - a,, "ULTRASOUNDS are used to detect flaws present inside a metal."),(E - b,, "Manjira, the ghatam, jal tarang are examples of Ghana vadya."):}`

Discussion

15.	If a uniform metal plate with a hole init heated then explain how the size of the hole gets effected?
Answer» Solution : The SIZE of the hole will increase due to thermal EXPANSIONS .When it si HEATED the distacne between any two MOLECULES increases .THUS the size of the hole increase

Discussion

16.	{:("Column A","Column B"),(A"Convex mirror",(" ")a."Dispersion of light"),(B."Concave mirror",(" ")b."Dentists"),(C."Plane mirror",(" ")c."Kaleidoscope"),(D."Prism",(" ")d."Street light reflectors"):}
Answer» Solution :A-d Convex mirror is USED as street light reflector. B-b A concave mirror is used by dentist. C-c PLANE mirror is used in kalcidoscope. D-a PRISM is used to observe the dispersion of light.

Discussion

17.	Choose the correct statement : - (A) In case of an electric cell, chemical energy is converted into electricalenergy. (B) combination of electric cells is called battery.
Answer» Only (A) is true. Only (B) is true. Both (A) and (B) true. Both (A) and (B) are false. Solution :Both the given statement are true. In the case of anelectric CELL, chemical energy is CONVERTED into elec-trical energy.And the COMBINATION of electric cell is called battery.

Discussion

18.	Water is a bad conductor of heat.
Answer» ANSWER :T

Discussion

19.	Electric bell works on 'heating effects of electric current'.
Answer» SOLUTION :Electric bell works on 'magnetic EFFECTS of electric CURRENT.

Discussion

20.	While determining the time period of a simple pendulum, why the time for 20 or more oscillations is found ?
Answer»

Discussion

21.	The charged particle in an atom that contributes positive charge is 'electron'.
Answer» SOLUTION :ELECTRON in an ATOM contributes to the NEGATIVE CHARGE.

Discussion

22.	Which among the following angles can be the maximum angle through which a divider can be streched to draw a circle ?
Answer» `180^(@)` `90^(@)` `45^(@)` `160^(@)` Solution :If theposition (angle) of the arms of a divider is as shown in figure, it is not POSSIBLE to draw a circle, and hecne, the maximum angle through which a divider can be strechted to draw a circ LE AMONG given OPTION is `160^(@)`

Discussion

23.	Choose the correct statement (a) Two thinwoolen blankets keep ou body warmer than a single equally thick woolen blanket (b) Mud houses with thatcvhed roofs keep warm in summer and cool in winter as compared to concrete housed
Answer» only a only b both a and b none of these Solution :Two thin woolen blanker are warmer than a THICK woolen blanket because there is an etra layer of air trapped between thin BLANKETS which acts as and insultort and does not ALLOW the HEAT form the body to flow out .mud houses with thatched rofs keep cool in summer and warm in winter as compareed to convretehouses because the thatched roof contains a large AMOUNT of trapped air . Hence in summer the heat form insie does not flow out. Thus they remain cool in summer and warm in winter

Discussion

24.	State whether all the bulbs we use work on the principle of heating effects of electric current ?
Answer» Solution :No, filament bulbs we use work on heatingeffect of ELECTRIC CURRENT . In these bulbs, in addition to light,lot unwanted heat is alsogenerated and this RESULTS in THEWASTAGE of electricity. We have different types of bulbs, known as fluoresent tubelights which work on a different principle. By using them we can reduce wastage of current. Compact fluorescentlamps (CFI). also reduce wastage can be fixed in the ordinary bulbs holders.

Discussion

25.	Explain how land and sea breezes occur.
Answer»

Discussion

26.	Black and dull surfaces are .............. of heat.
Answer» SOLUTION :GOOD ABSORBERS

Discussion

27.	The image formd by a concave mirror can be ______.
Answer» real virtual MAGNIFIED All of the above Solution :The IMAGE formed by a concave mirror is real or virtual depending on the POSITION of the object infront of the mirror. It is INVERTED or ERECT and magnified or diminished depending on the positionof the object infornt of the mirror.

Discussion

28.	Why are theadvantages and disadvantages in using a vice?
Answer» Solution :Viice is used to hold work pieces. Advantages : This tool is very useful if the work piece small. Piece of metal is to be cut. The metal is fixed between the jaws of the vice tightly and then it can be cut. Easily. Vice holds the objects to be WORKED on tightly at a position. So, the hands of theworker are free towork in the vice Disadvantages : Very thin and soft metals cannot be held on a vice . if it soft metal,the vice change its DIMENSION also it PUT some markings on the metal surface. SIMILARLY, a work piece of bigger size cannot be held in the vice.

Discussion

29.	A boy fires a gun and another boy at a distance of 1360 m hears the sound of firing the gun 4 s after its smoke is seen. Find the speed of sound.
Answer» Solution :Given: Distance d = 1360 m, time t = 4 s Distance d SPEED of SOUND V =d/t`= (1360m)/(4s)` ` = 340 MS^(-1)`

Discussion

30.	The amount of heat energy absorbed by the substance to change completely form liquid at its boiling point to gaseous state is ______J
Answer» 4618 2270 4538 4958 Solution :The SUBSTACNE in liquid STAE CHANGES to GASEOUS state byabsorbing energy of 2690-420 =2270 J

Discussion

31.	Solids expand the least and gases expand the most on being heated.
Answer» ANSWER :T

Discussion

32.	10 g of water occupies____cm^(3) of volume
Answer» ANSWER :10

Discussion

33.	Sound can travel in vacuum.
Answer» ANSWER :F

Discussion

34.	The number of vibrations made by a vibrating body in one second is called :
Answer» SOLUTION :FREQUENCY

Discussion

35.	write SI and CGS unit of any three physical quantities?
Answer»

Discussion

36.	Define amplitude and frequency. Write their SI units.
Answer»

Discussion

37.	The time period of a seconds pendulum is ______ s.
Answer» `1` `2` `4` `6` SOLUTION :A pendulum WHOSE time period is 2 s is CALLED seconds pendulum.

Discussion

38.	The temperature rises by 18^@F. What is the rise on the Celsius scale ?
Answer» SOLUTION :`10^@C`

Discussion

39.	A multipurpose tool can be used to cut wood
Answer» Solution :Wecan fix a carpenter's HAND SAW in MULTIPURPOSE tool and CUT WOOL

Discussion

40.	Which of the following is not a part of a hack saw ?
Answer» Blade Fixed jaw Handle Metallic frame Answer :B

Discussion

41.	100 g of ice at 0^(@)C is mixed with 0.25 kg of water at 0^(@)C The net transfer of heat is _______
Answer» SOLUTION :When 100 GOF ice at `0^(@)C` is mixed with 250 g of water at `0^(@)C` the net TRANSFER of heat energy is zero Because both are at same temperature

Discussion

42.	For a circuit to be complete, every part of it must be made up of conductors.
Answer» ANSWER :TRUE

Discussion

43.	what is the use of switch.
Answer» Solution :SWITCH is a DERIVE USED as maker or BREAKER of an ELECTRIC circuit.

Discussion

44.	Which of the following statement is/true?
Answer» celsius `.^@C` is the CGS unit of temperature `30^(@)C` =303 K when HEAT energy from one body to another the change in temperature of BODIES need not be equal all the above Solution :(i) C.G.C unit of temperture is DEGREE celsius `.^@C` (ii) `30^(@)C` =(30+273)K=303K (III) When heat energy flows from one body to another the change in temperature of the bodies need not be equal

Discussion

45.	When two bodies A and B are rubbed, they acquire charge by friction, If the charge on A is negative, then the charge on B is "_______".
Answer» ANSWER :POSITIVE

Discussion

46.	There is always some loss of energy in conversion from one form of energy to another form, so the total energy is not conserved. True/False.
Answer» ANSWER :F

Discussion

47.	Match the entries given in Column A with the appropriate ones in Column B. {:("Column A","Column B"),(A."A plane mirror",(" ")a."Luminous source"),(B."Virtual image",(" ")b."Can be caught on a screen."),(C."Reflection of light",(" ")c."Magnified"),(D."The Sun",(" ")d."Read"),(E."Real image",(" ")e."Vacuum"),(F."Prism",(" ")f."Image distance is equal to object distance."),(G."Image on the retina",(" ")g."Dispersion"),(H."Velocity of light is maximum",(" ")h."Persicope"):}
Answer» ANSWER :A : F B : H D : A E : B F : G G : D H : E

Discussion

48.	Describe an experiment to determine the melting point and boiling point of water
Answer»

Discussion

49.	Arrange the following steps of an experiment in a sequential order to determine the frequency of a simple pendulum. (A) Start the stop watch when the bob reaches the extreme position and count the number of oscillations.(B) Suspend a simple pendulum from a cork fixed to a stand. (C) Repeat the experiment and determine the time taken for 20 oscillations. (t_(2)) (D) Pull the bob of the simple pendulum from its initial position of rest and release. (E) Stop the stop watch at the end of 20 oscillations and determine the time taken to complete 20 oscillations (t_(1)). (F) Determine the average of t_(1) and t_(2) as t. (G) The time period of the oscillation is found using. T = (t)/(20) and frequency using, f = 1/T.
Answer» ADBCEFG AFEDBCG BDAECFG BDEFCAG Answer :C

Discussion

50.	Three bulbs are connected in a circuit in an identi-cal way. When a fourth bulb is also connectedto the same circuit in the same way, brightness is reduced then the bulbs are connected in "________"
Answer» SERIES parallel it can happen in both cases It is not possible Solution :When BULBS are CONNECTED in series, their BRIGHTNESS decreases.

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

The velocity of sound is ____ in air compared to that of water.

The density of water at 4^@C is:

One millisecond is _____part of a second.

Which of the following tools can be used to cut the metal plates of smallest thickness?

Periscope works on the pirnciple of ______ of light.

The sky appears blue due to scattering of light.

Sun light is not necessary for the growth of plants.

A piece of steel has a volume of 10 cm^(3) and a mass of 80 g. What is its density in: kg//m^(3)

Which of the following tools can be fixd in the colletof a multipurpose tool the drill holes in to a wooden plank?

Explain why, a ray of light passing through the centre of curvature of a convace mirror gets reflected back along the same path.

Convert 10^@C in kelvin

All solids expand by the same amount when heated to the same rise in temperature.

Assertion (A): Convex mirrors are used as rear view mirrors in vehicles. Reason:(R) : The field ivew of convex mirror is maximum and they form diminished images.

If a uniform metal plate with a hole init heated then explain how the size of the hole gets effected?

{:("Column A","Column B"),(A"Convex mirror",(" ")a."Dispersion of light"),(B."Concave mirror",(" ")b."Dentists"),(C."Plane mirror",(" ")c."Kaleidoscope"),(D."Prism",(" ")d."Street light reflectors"):}

Choose the correct statement : - (A) In case of an electric cell, chemical energy is converted into electricalenergy. (B) combination of electric cells is called battery.

Water is a bad conductor of heat.

Electric bell works on 'heating effects of electric current'.

While determining the time period of a simple pendulum, why the time for 20 or more oscillations is found ?

The charged particle in an atom that contributes positive charge is 'electron'.

Which among the following angles can be the maximum angle through which a divider can be streched to draw a circle ?

Choose the correct statement (a) Two thinwoolen blankets keep ou body warmer than a single equally thick woolen blanket (b) Mud houses with thatcvhed roofs keep warm in summer and cool in winter as compared to concrete housed

State whether all the bulbs we use work on the principle of heating effects of electric current ?

Explain how land and sea breezes occur.

Black and dull surfaces are .............. of heat.

The image formd by a concave mirror can be ______.

Why are theadvantages and disadvantages in using a vice?

A boy fires a gun and another boy at a distance of 1360 m hears the sound of firing the gun 4 s after its smoke is seen. Find the speed of sound.

The amount of heat energy absorbed by the substance to change completely form liquid at its boiling point to gaseous state is ______J

Solids expand the least and gases expand the most on being heated.

10 g of water occupies____cm^(3) of volume

Sound can travel in vacuum.

The number of vibrations made by a vibrating body in one second is called :

write SI and CGS unit of any three physical quantities?

Define amplitude and frequency. Write their SI units.

The time period of a seconds pendulum is ______ s.

The temperature rises by 18^@F. What is the rise on the Celsius scale ?

A multipurpose tool can be used to cut wood

Which of the following is not a part of a hack saw ?

100 g of ice at 0^(@)C is mixed with 0.25 kg of water at 0^(@)C The net transfer of heat is _______

For a circuit to be complete, every part of it must be made up of conductors.

what is the use of switch.

Which of the following statement is/true?

When two bodies A and B are rubbed, they acquire charge by friction, If the charge on A is negative, then the charge on B is "_______".

There is always some loss of energy in conversion from one form of energy to another form, so the total energy is not conserved. True/False.

Describe an experiment to determine the melting point and boiling point of water

Three bulbs are connected in a circuit in an identi-cal way. When a fourth bulb is also connectedto the same circuit in the same way, brightness is reduced then the bulbs are connected in "________"