821 + Interview Questions in Physics in Class 7

1.	If temperature of a substance increases the average kinetic energy of molecus ofthe substance _______.
Answer» Solution :Temperature is directly proportional to the AVERAGE kinetic ENERGY of molecules .As temperature increases average kinetic energy also INCREASE

Discussion

2.	Nichrome is the material used to make "______" elements.
Answer» SOLUTION :NICHROME is the MATERIAL used tomake HEATING ELEMENTS.

Discussion

3.	The mass of an empty density bottle is 50 g. When it is completely filledwith water, its mass is foundto be 100 g and when itiscompletly filledwith aliquid,its mass is 150 g. The density of the liquid is "_________" kg m^(-3).
Answer» (a) 2 (B) 2000 (C ) 3.5 (d) 3500 Solution :Mass of the empty density bottle, `m_(1)` = 50 " g " Mass of the bottle with water, `m_(2)` = 100 " g " Mass of the bottle with liquid, `m_(3)` = 150 " g " Volume, V=dxxm = 1XX 50 = 50 " " `cm^(3)` Density of liquid = "mass " of" liquid"/"volume " of " liquid" `(m_(3)-m_(1))/V=(150-50)/(100-50)` `100/50=2 " g "cm^(-3)`= 2000 " kg "m^(-3)`

Discussion

4.	Define conduction, convection and radiation
Answer»

Discussion

5.	When the Moon is not completely visible from the Earth, we call it _____ eclipse.
Answer» Solution :When the MOON is not COMPLETELY VISIBLE from the EARTH, we call it as TOTAL lunar eclipse.

Discussion

6.	A lorry dirvrer sees a old man crossing the road. Suddenly he applies brakes aned stops the lorry within 30s. If the initial speed of the lorry is 108 km h^(-1) . Find its deceleration.
Answer»

Discussion

7.	What is the mass of 5m^(3) of cement of density 2000 kg//m^(3) ?
Answer» SOLUTION :DENSITY= `2000 kg//m^(3)` volume `= 5M^(3)` `"MASS"= "Density" xx "volume"` `= 2000 xx 5=10000`kg

Discussion

8.	Name the differnet types of graphs used to reprsent motion of a body?
Answer»

Discussion

9.	Speedoneter is used to measuere the distance travelled by a vehicle.
Answer» SOLUTION :Speedometer is used to MEASURE the speed of a VEHICLE.

Discussion

10.	The motion of the pulley while drawing water from a well is _________ about is fixed axis
Answer» Solution :When the perosn pulls the rope OVERT the pulley, the pulley rotates about the axis which is PASSING through it, and HENCE the MOTION is ROTATORY

Discussion

11.	What happens when a glass rod is rubbed against a silk cloth?
Answer» the glass and actuires a positive charge DUE to LOSS of electrons. the silk CLOTH acquires negative charges due to gain of electrons. if these two bodies are again brought in CONTACT the net charge on them is zero. All the above. Solution :We KNOW that, a body which losses electrons acquires a positive charge and a body which gains electronsacquires a negative charge. And when these two charged bodies are brought in contact again, the net charge will be zero, due to neutralization of charge.

Discussion

12.	After reflecton, a light ray which is incident along the principal axis of a mirror,
Answer» RETRACES its PATH passes through center of curvature makes zero angle with the normal. All the above. Solution :The light ray which is incident along the PRINCIPAL axis of a mirror falls normally on the mirror, and hence, it retraces its path. From the figure it is clear that is passes through the centre of curvature. As the line passing through the centre of curvature is PERPENDICULAR to the mirror, the angle made by the light ray with the normal is zero.

Discussion

13.	Pitch depends on ...........
Answer» SOLUTION :FREQUENCY

Discussion

14.	Choose the correct statements in case of mulipurpose tools
Answer» We can PERFORM multiple tasks by FIXING diferent tools in its collet. It is not possible to drill holes by USING multipurpose tool We can fix a carpenters hand -saw in this tool and cut WOOD. Both (a) and (c) Solution :(i) We can perfrom multiple TAKS by fixing different tools in the collet of ta multpurpose tool. (ii)A carpenters' hand saw can be fixed in the collet of multipupose tool to cut wood (iii) By fixing a drill bit to his tool we can drill holes also.

Discussion

15.	Convert 4000cm^(2) to m^(2)
Answer» SOLUTION :`0.4 m^(2)`

Discussion

16.	According to law of conservation of energy, energy changes from one form to another form, but the total energy of that system
Answer» INCREASES DECREASES ALTERNATES REMAINS the same Answer :D

Discussion

17.	Which of the following is a bad conductor of electricity ?
Answer» Gold Copper Pure alcohol Living plant Solution :Among the GIVEN OPTIONS impure water is the BETTER con-ductor of electricity.

Discussion

18.	A leveller with one metre long metal strip is used to level the surface of the soil. If the farmer takesthe leveller from one end to another end of the field of length 265m hen calculate the area of the field which is levelled.
Answer» Solution : Length of the metal STRIP (L) =1m Length of the fiedl, `(l^(1))=25m` `:.` The are of field which can be levelled (A) `=l^(1)xxl` `25 mxx.1m` =25 squaremetre.

Discussion

19.	Which of the following isnot a depolarizer ?
Answer» POTASSIUM dichromate Copper sulphate Mercury oxide Manganese dioxide. Answer :C

Discussion

20.	If a body vibrates 20 times in a second, then its frequency is 20 Hz.
Answer» Solution :The number of vibrations completed in ONE second is CALLED its frequency. `THEREFORE` As the body is vibrating 20 TIMES in 1 s its frequency is 20 Hz.

Discussion

21.	The path of light is straight line.
Answer» SOLUTION :LIGHT TRAVELS in STRAIGHT LINES.

Discussion

22.	What is the mass of a piece of wood that has a density of 0.85 g//cm^(3) and a volume of 29.4 cm^(3)?
Answer» SOLUTION :Density = `0.85 G//cm^(3)` VOLUME = `29.4 cm^(3)` Mass = Volume `XX` Density = 24.99 g

Discussion

23.	Sitar, veena and violin are some _____ instruments.
Answer» ANSWER :D

Discussion

24.	Saket was repairing an electric bell. By mistake, instead of an electromagnet, he placed a permanent magnet in the electric bell. Explain, what changes do you observe.
Answer» Solution :Electromagnets are used in ELECTRIC bells. When current passes through the coil, the electromagnet attracts a metallic PLATE. The hammer attached to this metallic plate hits this gong and produces sound. When the plate is attracted by the electromagnet, it breaks the circuit and the electromagnet stops work-ing as a magnet and after hitting the gong, the plateretains its contact with contact scre. INSTEAD of an electromagnet, if we USE a NORMAL magnet, the metal-lic plate cannot regin its original contact.

Discussion

25.	Explain the formation of real and virtual images. Discuss what kind of images are formed in plane, convex and concave mirrors.
Answer» Solution :The image which cannot be caught on a screen is called virtual image and which can be caught on the screen is called real image. Real images are formed by a convergent beam of light rays, and virtual images are formed by a DIVERGENT beam of light rays. (i) The image formed by a PLANE mirror is virtual in NATURE and always erect but laterally inverted adn same in size as that of object. (ii) The image formed by convex mirror is always erect, virtual in nature but smaller in size than that of object. (iv) The image formed by concave mirror is EITHER real or virtual and it may be inverted or erect, DEPENDING on the position of object in front of it.

Discussion

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

Discussion

27.	{:("Column A", "Column B"),((A)"Rest and motion",(a)" car taking a turn"),((B)"Oscillatory and periodic",(b)"Relative"),((C)"Translatory and rotatory",(c)"motion of the bob of a simple pendulum"),((D)"Variable velocity",(d)"Motion of the wheels of a bicycle in motion"):}
Answer» ` A to b, B to c, C to d, D to a` ` A to b, B to c, C to d, D to d ` `A to c, B to b, C to d, D to a` `A to a, B to c, C to b, D to d` Solution :A -B Rest and motion are RELATIVE. B-c Motion of the bob of a SIMPLE pendulum is oscillatory as WELL as periodic. C-dThewheels of a bicyle in motion PERFORM both rotatory and translatory motions. D-aA car taking a turn is example of varable velocity.

Discussion

28.	Convert 5000cm^(3) to m^(3)
Answer» SOLUTION :`0.005 m^(3)`

Discussion

29.	A graph is drawn by taking the rise in temperature on Y axis and heat supplied on x axis .Find out the melting point and boiling point of heat substance
Answer» SOLUTION :Melting point =`5^(@)C` BOLING point =` 80^(@)C`

Discussion

30.	Water freezes at 32^@F What will be the temperature in degree Celsius and K
Answer» Solution :`C= 5/9 (F-32) = 5/9 (32-32) = 5 XX 0/9` 0 DEGREE celsius for `0^@ C` In K = 0 + 273 = 273 K

Discussion

31.	When the screw used tofix the object between the jaws is rotated in the clockswise direction, then the _________ jaw moves towards __________
Answer» ANSWER : MOVABLE, FIXED

Discussion

32.	Which of the following is not a part of wooden plough?
Answer» Handle BLADE Long POLE None of the above Solution :Handle, blade and long pole are PART of the wooden plough.

Discussion

33.	A paper cutting is placedon a graph as shownin the figure, each on he X and Y axes represens a distance of2 cm. The area of the paper cutting is "_________"Cm^(2).
Answer» (a) 378 (b)186 (c ) 312 (d) 156 Solution :We can DIVIDE the PAPER CUTTING into 3 rectangles of dimension `(9xx3), (11xx3),(9xx2)`. Area = `(9xx3) + (11xx3) + (9xx2)` = 78 , but 1 div= 2 cm Area = 78 XX 4 = 312 " " `cm^(2)`

Discussion

34.	Triangulation method is used to determine the distance between two places A and C. A triangle obtained to a reduced scale is as shown below The ratio of the actual distances from C to another place B: and A to B is 5. Determine the distance between A and C. The actual distance between B and C is 20 km.
Answer» Solution :The distance between the places A and B to reduced SCALE =5 cm `"BC"/"AB"=5` `"20"/"5 X"=5` `"20"/"25"=⅘` Distance between A and C = `4/5 xx10 = 8 " km "`

Discussion

35.	Ramu took four indentical iron balls of temperature 36^(@)C,10^(@)C,20^(@)C and 32^(@)C .He kept them in physical(thermal) contact with one another .After some time hemeasured the equilibrium temperautre attained by these four balls .What is the value of the equilibriumtemperature?
Answer» SOLUTION :As the four bodies are indentical the equilibrium temperature is theaverage of the temperature That is `t=t_(1)+t_(2)+t_(3)+t_(4)/(4)` `=(6+10+20+32)/(4)`

Discussion

36.	Telephone wires are kept tight between two poles in summer
Answer» ANSWER :F

Discussion

37.	Describe an experiment to show that the solids expand on heating
Answer»

Discussion

38.	Answer the following question What is the speicfic heat capacity of water in different system of units?
Answer»

Discussion

39.	In case of an incense stick or an agrbati the smoke at the lighted end of stick moves in upward direction it is because
Answer» the cool air below the LIGHTED end moves to take the place of hot air above the lighted end the air at the hot ends is more dense it is natural for the smoke to move up the smoke is repelled by the gravity of earth Solution :In case of an INCENSE STICK the air at the lighted end is hot and hence volume INCREASE and density decrease so it rises up (moves up) the air at the hot end is ata higher temperatureso its density is LESS and this lesser dense air rises up and more dense air occupies this place so it is due to convection of gases

Discussion

40.	Arrange the following steps in a sequential order to demonstrate the thermal expansion of solids (a) heat th eball with a spirit lamp for some time (b) place the ball on the ring it just slips through the ring (c ) Place the ball on the ring the ball does not pass through the ring (d) take a ball and ring such that the internal diameter of the ring and the external diameter of the bal are equal .
Answer» DBAC dabc dacb dcab Solution :First take a ball and rightsuch that the INTERNAL DIAMETER of the ring and the eternal diameter of the ball are EQUAL (d) .Place the abll onthe ring it just slips through the ring (b) Now heat theball witha spirit LAMP for some time (a) and then again place the ball onthe ring the ball does not pass through the ring (c ) This expains that the ball expands on heating and it does not pass through the ring

Discussion

41.	Sea breeze and land breeze are formed due to
Answer» conduction convenction RADIATION all the above Solution :Sea BREEZE and LAND breeze are FORMED DUE to convection

Discussion

42.	Raju was trying very hard to unscrew the metal cap of a bottle then he heated the cap slightly and was able to unscrew it easily explain
Answer» Solution :When the CAP is HEATED it expand more than bottler THUS we can EASILY unscrew the cap

Discussion

43.	What is the image distance of an object which is placed at an infinite distance ?
Answer» the radius of curvature of the spheical mirror. the FOCAL length of the SPHERICAL mirror. infinity, in CASE of the plane mirror. Both (b) and (c) Solution :The image of an object which is placed at an infinite distance will be formed at the focus in case of convex and concave mirrors whereas, it is equal to infinity in the case of plane mirror.

Discussion

44.	The image distance of an object which is placed at an infinite distance is equal to
Answer» the RADIUS of curvature of the spheical mirror. the focal length of the spherical mirror. infinite in CASE of plane mirror. Both (b) and (c) Solution :The image of an object which is placed at an infinite distance will be formed at the focus in case of convex and CONCAVE mirrors whereas, it is equal to INFINITY in the case of plane mirror.

Discussion

45.	For each of the equation four choices have been provided. select the correct alternative Which of the following statement is/are wrong?
Answer» NORMALLY solids expands on melting normally a liquid contract on FREEZING there is no EFFECT on volume during COOLING or heating a gas all the above Answer :c

Discussion

46.	For each of theequation four choices have been provided .select the correct alternative Choose the correct statement: (a) boiling of a given substacne takes place at all temperature (b) evaporation of a substance takes place at a constant temperature (c ) boiling takes place at every part of the liquid (d) evaporation takes place only on the surface of liquid
Answer» both a and C B,c and d both c and d all the above ANSWER :c

Discussion

47.	For each of theequation four choices have been provided .select the correct alternative Choose the correct statement: (a) when heat energy is given to ice at 0^(@)C th peotential energy of the molecules of ice increases (b) heat added to ice at 0^(@)C does not increase the kinetic energy and hence thereis no rise of temperature
Answer» only a only B both a and b NONE of these Answer :C

Discussion

48.	Choose the correct statement in winter (a) a set of double window is a better insulator (b) window constructed of a single double thickness glass is a good insultor
Answer» only a only B both a and b cannot be compared Answer :a

Discussion

49.	If more energy is spent to set a body into vibration, then
Answer» the amplitude of vibrating body is more. the amplitude of vibrating body is less. the amplitude of vibrating body always RAMAINS same even after setting it into vibration. Both (B) and (c). SOLUTION :The more is the energy SPENT or set the body into vibration, the more is the amplitude of the vibration.

Discussion

50.	The time taken to perform 30 vibrations is 30 times the time taken for a single vibration.
Answer» SOLUTION :LET the time taken for one VIBRATION be T. `therefore` Time taken for 30 vibration = 30 T `= 30 (T)` `= 30 XX` (Time taken for single vibration)

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

If temperature of a substance increases the average kinetic energy of molecus ofthe substance _______.

Nichrome is the material used to make "______" elements.

The mass of an empty density bottle is 50 g. When it is completely filledwith water, its mass is foundto be 100 g and when itiscompletly filledwith aliquid,its mass is 150 g. The density of the liquid is "_________" kg m^(-3).

Define conduction, convection and radiation

When the Moon is not completely visible from the Earth, we call it _____ eclipse.

A lorry dirvrer sees a old man crossing the road. Suddenly he applies brakes aned stops the lorry within 30s. If the initial speed of the lorry is 108 km h^(-1) . Find its deceleration.

What is the mass of 5m^(3) of cement of density 2000 kg//m^(3) ?

Name the differnet types of graphs used to reprsent motion of a body?

Speedoneter is used to measuere the distance travelled by a vehicle.

The motion of the pulley while drawing water from a well is _________ about is fixed axis

What happens when a glass rod is rubbed against a silk cloth?

After reflecton, a light ray which is incident along the principal axis of a mirror,

Pitch depends on ...........

Choose the correct statements in case of mulipurpose tools

Convert 4000cm^(2) to m^(2)

According to law of conservation of energy, energy changes from one form to another form, but the total energy of that system

Which of the following is a bad conductor of electricity ?

A leveller with one metre long metal strip is used to level the surface of the soil. If the farmer takesthe leveller from one end to another end of the field of length 265m hen calculate the area of the field which is levelled.

Which of the following isnot a depolarizer ?

If a body vibrates 20 times in a second, then its frequency is 20 Hz.

The path of light is straight line.

What is the mass of a piece of wood that has a density of 0.85 g//cm^(3) and a volume of 29.4 cm^(3)?

Sitar, veena and violin are some _____ instruments.

Saket was repairing an electric bell. By mistake, instead of an electromagnet, he placed a permanent magnet in the electric bell. Explain, what changes do you observe.

Explain the formation of real and virtual images. Discuss what kind of images are formed in plane, convex and concave mirrors.

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

{:("Column A", "Column B"),((A)"Rest and motion",(a)" car taking a turn"),((B)"Oscillatory and periodic",(b)"Relative"),((C)"Translatory and rotatory",(c)"motion of the bob of a simple pendulum"),((D)"Variable velocity",(d)"Motion of the wheels of a bicycle in motion"):}

Convert 5000cm^(3) to m^(3)

A graph is drawn by taking the rise in temperature on Y axis and heat supplied on x axis .Find out the melting point and boiling point of heat substance

Water freezes at 32^@F What will be the temperature in degree Celsius and K

When the screw used tofix the object between the jaws is rotated in the clockswise direction, then the _________ jaw moves towards __________

Which of the following is not a part of wooden plough?

A paper cutting is placedon a graph as shownin the figure, each on he X and Y axes represens a distance of2 cm. The area of the paper cutting is "_________"Cm^(2).

Ramu took four indentical iron balls of temperature 36^(@)C,10^(@)C,20^(@)C and 32^(@)C .He kept them in physical(thermal) contact with one another .After some time hemeasured the equilibrium temperautre attained by these four balls .What is the value of the equilibriumtemperature?

Telephone wires are kept tight between two poles in summer

Describe an experiment to show that the solids expand on heating

Answer the following question What is the speicfic heat capacity of water in different system of units?

In case of an incense stick or an agrbati the smoke at the lighted end of stick moves in upward direction it is because

Sea breeze and land breeze are formed due to

Raju was trying very hard to unscrew the metal cap of a bottle then he heated the cap slightly and was able to unscrew it easily explain

What is the image distance of an object which is placed at an infinite distance ?

The image distance of an object which is placed at an infinite distance is equal to

For each of the equation four choices have been provided. select the correct alternative Which of the following statement is/are wrong?

Choose the correct statement in winter (a) a set of double window is a better insulator (b) window constructed of a single double thickness glass is a good insultor

If more energy is spent to set a body into vibration, then

The time taken to perform 30 vibrations is 30 times the time taken for a single vibration.

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

When the screw used tofix the object between the jaws is rotated in the clockswise direction, then the _ jaw moves towards __