821 + Interview Questions in Physics in Class 7

1.	Which of the following is/are units of weight?
Answer» `N` g f kg f All the above Solution :N, KGF and gf are UNITS of weight.

Discussion

2.	Describe the electrostatic force that exists between A and B in the following cases.
Answer» Solution :(a) Both A andB are netural , hence, no ELECTROSTATIC force. (b) and (c ) As one of them is charged thereexists an ATTRACTIVE force due to INTRODUCTION. (d) As A and B are oppositely charged, there exists an attractive force between them. (E) and (f) As A and B are IDENTICALLY charged, there exists a repulsive froce between them.

Discussion

3.	In general, the voice of a woman has a _____ than that of a man.
Answer» ANSWER :C

Discussion

4.	If 103 cm^(3) of aluminium has a mass of 0.280 kg. Find its density inkg//m^(3)
Answer» SOLUTION :`2700 kg//m^(3)`

Discussion

5.	"_______" is a device used to detect the presence and the nature of the charge on a body.
Answer» ANSWER :ELECTROSCOPE

Discussion

6.	A piece of steel has a volume of 10 cm^(3) and a mass of 80 g. What is its density in: g//cm^(3)
Answer» Solution :VOLUME of STEEL =` 10 cm^(3)` Mass of steel = 80G DENSITY of steel = `"Mass"//"Volume"` `= 80//10= 8g//cm^(3)`

Discussion

7.	Mercury coated on zinc plate prevents the impuri-ties from coming into contact with acid and prevents "______".
Answer» Solution :MERCURY coated on ZINC PLATE prevents the IMPURITIES from conming into contact with ACID and prevents local action.

Discussion

8.	Which of the following agent (s) is (are) used to pull a plough?
Answer» TRACTOR Bull Man Both (a) and (B) ANSWER :D

Discussion

9.	Choose the correct statement(s) in case of a voltric cell. (A) Cathode used is Zn and anode used is copper. (B) The electrolyte used is dilute sulphuric acid.
Answer» Only A is true Only B is true Both A and B are true Both A and B are false Solution :In voltaic cell zinc is the NEGATIVE electrode , i.e, cath-ode and copper is the positive electrode, i.e., ANODE. The ELECTROLYTE used is dilute sulphric acid.

Discussion

10.	Loudness of a sound depends on ........
Answer» ANSWER :F

Discussion

11.	The densities of two liquids A and B are in the ratio 15 : 2 If their masses are equal, write the following steps in a sequential order to determine the ratio of their volumes.
Answer» (a) Write the relation between DENSITY, mass and VOLUME for each of the liquid A and B. (b) Note the ratio of densities,`d_(A)/d_(B)=15/2` and `m_(A)=m_(g)` Divide the twoequations and get the VOLUMES of the two liquids using `V_(A)/V_(B)=d_(B)/d_(A)` (d) Substitute the given value in the above formula and find the ratio of `V_(A) to V_(B)`. Solution :Write the ratio of densities as given, `(d_(A))/(d_(B))=15/2` and the mass of A is equal to mass of B. Write the relation between mass, density and volume for the liquids A and B. Divide the density of A and density of B and get the relation `V_(A)/V_(B)-d_(B)/d_(A)`. Substitute the given ratio of `v_(A) to V_(B)`.

Discussion

12.	A major component of an electric bell is "______".
Answer» SOLUTION :An ELECTROMAGNET is a MAJOR COMPONENT of an elec-tric BELL.

Discussion

13.	Convert 2m^(3) into cm^(3)
Answer» SOLUTION :`2000000 CM^(3)`

Discussion

14.	The unit of force in SI system is newton and it is given as 1 newton = 1kg m s^(-2). In CGS system its unit is dyne and it is given as 1 dyne = 1 g cm s^(2). Arrange the following steps in a sequential order to relate the SI unit and CGS unit of force. (a) Write the conversations of kg and m, into g and cm, respectively. (b) Substitute the conversations in 1 newton = 1 kg m s^(2)Write the relation between 1 newton and dyne. (d) Write in place of 1 g cm s^(-2) as 1 dyne
Answer» a c b d a b d c b d a c c d a b Solution :The SI unit of FORCE is newton, 1newton = 1 KG m `s^(2)` . First convert kg and m into G and cm. SUBSTITUTE these conversations in 1 newton = 1 kg m ` s^(-2)` . Now in the place of 1 g cm ``s^(-2)`, write 1 DYNE as 1 newton = `10 ^(5)` dyne.

Discussion

15.	Weight of a body varies according to the variation in the______.
Answer» ANSWER :VALUE of 'G'

Discussion

16.	"_______" is a used to protect builiding from lightning.
Answer» ANSWER :LIGHTNING CONDUCTOR

Discussion

17.	{:("Column A", "Column B"),(A."cicular motion",a."Vechicle crossing over a fly-over bridge"),(B."Rectilinear motion",b."One to-and-fro-motion"),(C."Curvilinear motion",c."Distance-time graph is a straight line"),(D. (v-u)/a,d.100cm),(E."Constant speed",e."Time (t)"),(F."Oscillation",f."A spinning top"),(G."The length of a seconds pendulum" ("taking" g=10ms^(-2)),g."Coin moving over a carrom board"):}
Answer» ANSWER :A::B::C::D

Discussion

18.	The pitch of sound is determined by the ______ of vibration.
Answer» FREQUENCY amplitude velocity None of these Solution :The PITCH of SOUND is DETERMINED by the frequency of VIBRATION.

Discussion

19.	Convert 1 ml into cm^(3).
Answer» SOLUTION :1 ML=`1CM^(3)`

Discussion

20.	Assertion (A): A convex mirror always forms a diminished and virtual image. Reason (R): The laws of reflection are not applicable in the case of shpherical mirrors.
Answer» Both A and R are conrrent and R is the correct 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 :In the CASE of a convex mirror the nature of the and IMAGE FORMED is always diminished and it is a virtrual and erect image. So A is correct but R is incorrect because the laws of reflection are applicable in all TYPES of mirrors INCLUDING spherical mirrors.

Discussion

21.	A boy walks a distance of 30 m in 1 minute and another 30 m in 1.5 minute. Describe the type of motion of the boy and find his average speed in ms^(-1)
Answer» SOLUTION :non-uniform. `0.4 m s^(-1)`

Discussion

22.	The colour of an opaque object is the colour of light which it.........
Answer» SOLUTION :REFLECTS

Discussion

23.	What is the nature of materials used to make the 'filament' of an electric bulb and the 'fuse wire' used in electric fuse ? Compare them.
Answer» Solution :A filament used INA bulb must withstand the high temperature to emit light. The material used to make filament must have high resistance and high melting point. Usually tungsten is used to make a filament. The fuse wire must get heated and melt whenever excess current PASSES through it. Hence, it must bemade of an alloy with high resistance and LOW melt-ing point. Usually an alloy of lead and tin is used for this PURPOSE.

Discussion

24.	Sound travels much faster than light in a given medium.
Answer» Solution :VELOCITY of light is more than the velocity of SOUND in a given MEDIUM, i.e., light travels FASTER than sound in a given medium.

Discussion

25.	The time period of a simple pendulum is independent of _______ of oscillation.
Answer» SOLUTION :The time period of a SIMPLE pendulum is INDEPENDENT is amplitude of OSCILLATION.

Discussion

26.	We can hear sounds of frequency in the range of ............
Answer» 10 HZ 500 Hz 100,000 Hz 50,000 Hz. Answer :B

Discussion

27.	A rose appears red in light of all the colours.
Answer» ANSWER :F

Discussion

28.	Read the following statements and choose the correct option. (A) The angle made by the incident light ray with the plane of mirror is equal to the angle made by the reflected light ray with the plane of mirror. (B) The angle between an incident light ray and a reflected light ray is twice that of the angle between the incident light ray and normal.
Answer» Only A is true Only B is true Both A and B are true Both A and B are false Solution : (i) From the figures: i=r (first law of REFLECTION). ANGLE made by the incident RAY with the plane of MIRROR is `anglePOM=90-i=90-r""(2)` The angle made by the reflected ray with the plane of mirror =90-r ""(2) (iii) `anglePOQ=anglePON+angleNOQ` `=i+r=i+i(anglei=r)` Angle between incident and reflected ray =2 (angle of incidence).

Discussion

29.	An objcet is placed between two mirrors which make an angle of 45^(@) with each other, then the number of images formed are _____.
Answer» 8 7 2 infinite Solution :The number of IMAGE FORMED `(N)=(360)/(theta)-1` `=(360)/(45)-1` `=8-1=7`

Discussion

30.	We can use a simple pendulum to measure the time.
Answer» SOLUTION :The MOTION of a SIMPLE PENDULUM is PERIODIC

Discussion

31.	The density of water is maximum at 4^@C.
Answer» ANSWER :T

Discussion

32.	Two electric bulbs of 100 W each is used for 10 hours in the month of June. Write the following steps in sequential order to find the numbe of units of electricity consumed in the month of June. (A) The number of units of electricity consumed by both bulbs in the month of June is the total elec-trical energy consumed by bulbs expressed in W h divided by 100 W h . (B) Note the rated power of each electric bulb, time of electrical consumption of each bulb per day from the given data. (C ) We know, one electrical unit = 1 kW h or 1000 W h. (D) Calculate the amount of electrical energy con-sumed by both the bulbs in the month of June using, (sum of the electrical power of both the bulb) xx (time of consumption in one day) xx 30 days.
Answer» BACD ABCD BDCA DCBA Solution :The POWER of electric bulb, `P = 100 W`. The TIME for which bulb utilieses electric power per day `= 10` h. In the month of june, `t = 10 h xx 30` days `= 300 h`. The electric energy consumed by a bulb is `= P xx t` `= 100 xx 300= 32 xx 10^(4) W h` `= 30 k Wh` The total energy consumed by both the bulbs, `E = 2 xx 20 kWh = 60 kW h`. `:.` The number of electric units `= 60` units. `(ne 1 "unit" = 1 kW h)`

Discussion

33.	A hot metallic piece is placed in tap water contained in a bucket. Heat will flow from ..............to..........
Answer» SOLUTION :METALLIC PIECE, WATER

Discussion

34.	Name the phyical quantity that mesures fastness or slownes of a moving object.
Answer»

Discussion

35.	The maximum possible displacement of a vibrating body from its mean position during its motion is equal to
Answer» its amplitude half its amplitude twice its amplitude its frequency Solution :The MAXIMUM displacement of a VIBRATING BODY from its MEAN POSITION is called amplitude.

Discussion

36.	A string is stretched over two rigid supports and a weight of 1 kgwt is suspended from one of its free ends and then it is plucked. If the length of string over two rigid supports is decreased and plucked again, then the frequency of sound produced
Answer» in the first CASE is more. in the SECOND case is more. in both the CASES is EQUAL. Cannot be determined Answer :B

Discussion

37.	The image of an object is formed at infinite distance from a concave mirror. The position of the object is _______.
Answer» at C between C and F at F between POLE and F Solution :When the oject is placed at the principal focus (F), the image is formed at INFINITE DISTANCE.

Discussion

38.	The angle between the incident ray and the ray reflected from the plane mirror is 70^@. The angle of incidence will be:
Answer» `70^@` `30^@` `35^@` `90^@` ANSWER :C

Discussion

39.	If a bus travels a distance of 30 km in 45 minutes. What will be its speed in: m//"s "
Answer» Solution :DISTANCE COVERED in m `30 XX 1000=30000m` SPEED in `m//s= 30000//2700=11.11m//s`

Discussion

40.	For each of theequation four choices have been provided. select the correct alternative In case of an incense stick or an agarbatti 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 Answer :a

Discussion

41.	A glass rod is rubbed against a silk cloth, then
Answer» the glass rod acquires a positive charge due to LOSS of ELECTRONS. the silk CLOTH acquires negative charge 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 LOSES electrons acquires a positive charge and a body which GAINS electrons acquires a negative charge. And whenthese two charged bodies are brought in contact again, the net charge will be zero,due to neutralization of charge.

Discussion

42.	A car travels 40 km in the first hour, 45 km in the second hour, and 35 km in the third hour. Calculate the average speed of the vehicle in km/h and m/s.
Answer» SOLUTION :40 km/h, 11.11 m/s

Discussion

43.	The incident ray, the reflected ray and the normal lie............
Answer» SOLUTION :in ONE PLANE

Discussion

44.	Indentify the correct statement/s related to local action in a voltaic cell. (a) Carbon and iron particles present in zinc plate act as impurities. (b) Impurities react with acid and with the zinc par-ticles to form a large number of tiny cells creat-ing local electric circuits.
Answer» Only (A) is true. Only (B) is true. Both (A) and (B) true. Both (A) and (B) false. Solution :CARBON and iron particles present in zinc plate act as IMPURITIES and these particles react with acid and with the zinc particles to form a large NUMBER of tiny cells. The RESULTS in local action in a voltaic cell.

Discussion

45.	The brass of cap of the carbon and the zinc can of the dry cll actas "_______" and "______" poles, respectively.
Answer» positive, negative positive, positive negative, positive negative, negative Solution :The brass CAP of the CARBON ROD and the zinc can of the dry cell act as positive and negativepoles, respectively.

Discussion

46.	Fill in the blanks When hot water is poured in ordinary glass vessel it breaks because of ___________.
Answer» ANSWER :UNEVEN EXPANSION

Discussion

47.	A thick metallic cylindrical rod which is to be cut when placed between th jasws of a 'vice' the handle to roated though 4xx360^(@), if the distance moved by the movable jaws is 0.5 cm per rotation then calculate the radius of the rod. (Assume that initially th jawsare in contact with each other)
Answer» Solution : From the question it is clear that the handle was rotated through '4' rotations (N) . `:. n=4` The distance moved by the movable jaw per rotation `=0.5cm` `:.` TOTAL distance moved bythe jaw `=4 xx0.5cm 2cm` `:.` The DIAMETER of the rod = distance between JAWS when the rod is placedbetween them `d=2m` `rArr 2r=2 cm rArrr=1` `:.` Radius of the rod =1 cm

Discussion

48.	When bulbs are connected to the same source, the brightness of bulbconnected in parallel is "________" then the brightness of identical bulbs connected in series.
Answer» SOLUTION :When the bulbs are connected to the same source the brightness of bulbs connected in PARALLEL is more than the brightness of IDENTICAL bulbs connected in SERIES.

Discussion

49.	Sound travels the fastest in:
Answer» liquids SOLIDS gases VACUUM Answer :B

Discussion

50.	Ratan saw a flash of lightning and after sometime heard the sound of thunder. If the time gap between seeing and hearing is 3 s, then write the following steps in sequence to find the height from the ground where the lightning is produced. (a) Consider the velocity of sound (v) as 330 ms^(-1). (b) Note the time gap (t) between seeing and hearing. (c) From the formula, speed = ("distance")/("time taken"), height at which lightning was produced = speed of sound xx time interval. (d) Substitute the values in the equation (1) and find the value of the height of the lightning from the ground.
Answer» b a c d b c a d c b d a d a b c Solution :From the given data, time gap = 3 s. We know, `v = 330 MS^(-1)` Speed `= ("distance")/("time") to (c)` Neglecting the time taken by the light to reach the GROUND because VELOCITY of light is very LARGE, that is, `C = 3 xx 10^(8) ms^(-1)`. On substituting the value, the height of the lightning from the ground is equal to `330 xx 3 = 990 m.`

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

Which of the following is/are units of weight?

Describe the electrostatic force that exists between A and B in the following cases.

In general, the voice of a woman has a _____ than that of a man.

If 103 cm^(3) of aluminium has a mass of 0.280 kg. Find its density inkg//m^(3)

"_______" is a device used to detect the presence and the nature of the charge on a body.

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

Mercury coated on zinc plate prevents the impuri-ties from coming into contact with acid and prevents "______".

Which of the following agent (s) is (are) used to pull a plough?

Choose the correct statement(s) in case of a voltric cell. (A) Cathode used is Zn and anode used is copper. (B) The electrolyte used is dilute sulphuric acid.

Loudness of a sound depends on ........

The densities of two liquids A and B are in the ratio 15 : 2 If their masses are equal, write the following steps in a sequential order to determine the ratio of their volumes.

A major component of an electric bell is "______".

Convert 2m^(3) into cm^(3)

Weight of a body varies according to the variation in the______.

"_______" is a used to protect builiding from lightning.

The pitch of sound is determined by the ______ of vibration.

Convert 1 ml into cm^(3).

Assertion (A): A convex mirror always forms a diminished and virtual image. Reason (R): The laws of reflection are not applicable in the case of shpherical mirrors.

A boy walks a distance of 30 m in 1 minute and another 30 m in 1.5 minute. Describe the type of motion of the boy and find his average speed in ms^(-1)

The colour of an opaque object is the colour of light which it.........

What is the nature of materials used to make the 'filament' of an electric bulb and the 'fuse wire' used in electric fuse ? Compare them.

Sound travels much faster than light in a given medium.

The time period of a simple pendulum is independent of _______ of oscillation.

We can hear sounds of frequency in the range of ............

A rose appears red in light of all the colours.

An objcet is placed between two mirrors which make an angle of 45^(@) with each other, then the number of images formed are _____.

We can use a simple pendulum to measure the time.

The density of water is maximum at 4^@C.

A hot metallic piece is placed in tap water contained in a bucket. Heat will flow from ..............to..........

Name the phyical quantity that mesures fastness or slownes of a moving object.

The maximum possible displacement of a vibrating body from its mean position during its motion is equal to

A string is stretched over two rigid supports and a weight of 1 kgwt is suspended from one of its free ends and then it is plucked. If the length of string over two rigid supports is decreased and plucked again, then the frequency of sound produced

The image of an object is formed at infinite distance from a concave mirror. The position of the object is _______.

The angle between the incident ray and the ray reflected from the plane mirror is 70^@. The angle of incidence will be:

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

For each of theequation four choices have been provided. select the correct alternative In case of an incense stick or an agarbatti the smoke at the lighted end of stick moves in upward direction it is because

A glass rod is rubbed against a silk cloth, then

A car travels 40 km in the first hour, 45 km in the second hour, and 35 km in the third hour. Calculate the average speed of the vehicle in km/h and m/s.

The incident ray, the reflected ray and the normal lie............

Indentify the correct statement/s related to local action in a voltaic cell. (a) Carbon and iron particles present in zinc plate act as impurities. (b) Impurities react with acid and with the zinc par-ticles to form a large number of tiny cells creat-ing local electric circuits.

The brass of cap of the carbon and the zinc can of the dry cll actas "_______" and "______" poles, respectively.

Fill in the blanks When hot water is poured in ordinary glass vessel it breaks because of ___________.

A thick metallic cylindrical rod which is to be cut when placed between th jasws of a 'vice' the handle to roated though 4xx360^(@), if the distance moved by the movable jaws is 0.5 cm per rotation then calculate the radius of the rod. (Assume that initially th jawsare in contact with each other)

When bulbs are connected to the same source, the brightness of bulbconnected in parallel is "________" then the brightness of identical bulbs connected in series.

Sound travels the fastest in:

The brass of cap of the carbon and the zinc can of the dry cll actas "_" and "" poles, respectively.