821 + Interview Questions in Physics in Class 7

1.	Answer the following question What is the principle of thermometer?
Answer»

Discussion

2.	______is the force with which the earth pulls a body towards its centre.
Answer» Solution :WEIGHT is the force with whichthe earth PULLS a BODY TOWARDS its centre.

Discussion

3.	on heating substance of the following physical quantities change(s)?
Answer» density MASS volume both a and c Solution :On heating susbtance either EXPAND or contract i.e their volume (either CHANGE in LENGTH or change in are) change and heance density CHANGES but mass remains the same

Discussion

4.	Geometric centere of a mirror is called _______ mirror.
Answer» POLE PRINCIPLE focus optic centre centre of curvature Solution :GEOMETRIC of a MIRROR is CALLED pole of the mirror.

Discussion

5.	Oli paper is an example of _____ medium of light.
Answer» Solution :OLI paper is an example of translucent MEDIUM of LIGHT.

Discussion

6.	For each of theequation four choices have been provided .select the correct alternative A thermometer workd on the principal of
Answer» LINEAR expansion of solid cubical expansion of solid uniform expansion of volume of LIQUID or GAS with temperature both b and C ANSWER :c

Discussion

7.	Fill in the blanks The temperature at which a liquid convert to gaseous state is called ________ of a liquid.
Answer» ANSWER :BOILING POINT

Discussion

8.	When the Earth comes into the umbra and penumbra of the Moon, _____ is formed.
Answer» LUNAR ecilpse solar eclipse partial lunar eclipse None of the above. Answer :B

Discussion

9.	The density of gold is 19g//cm^(3) find the volume of 38 g
Answer» SOLUTION :`2 CM^(3)`

Discussion

10.	For each of theequation four choices have been provided .select the correct alternative Bimetallic strip works on the principal of ______
Answer» undequal EXPANSION of SOLIDS unequal contraction of solids equal expansion of solids Both a and B Answer :d

Discussion

11.	Choose the correct statement from the following.
Answer» Light CAUSES sensation of VISION. The sensation of heat is due to the presence of INFRARED radiation. Light TRAVELS in a straight LINE. All the above. Solution :(1) Light causes sensation of vision. (2) The sensatio of heat is due to the presence of infared radiation. (3) Light travels in a straight line.

Discussion

12.	One wants to see a magnified image of an object in a mirror. What type of mirror should one use ?
Answer» CONCAVE plane convex CENTRE of curvature Solution :Only concave MIRRORS FORM magified IMAGES.

Discussion

13.	An object is placed in front of a mirror. Arrange the following steps in sequential order to determine the nature of the mirror. (A) Check whether the image formed is virtual or real. (B) Check whether the virtual image formed is dimished, magnified or same size as that of the object. (C) If the image formed is real, the mirror used is concave. (D) If a magnified vritual image is formed, the mirror is concave, if a dimished virtual image is formed, the morror is convex and if size of the image is equal to the size of the object, plane mirror is used.
Answer» ACBD BDCA ACDB BADC Answer :A

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14.	Mention the different units of time and speed.
Answer»

Discussion

15.	Electricity can flow through :
Answer» wood rubber plastic COPPER WIRE Solution :copper wire

Discussion

16.	In an electric fan, electrical energy changes into mechanical energy. True/False.
Answer» ANSWER :T

Discussion

17.	1 kHz = __________ Hz.
Answer» SOLUTION :`1 KHZ = 1000 HZ`

Discussion

18.	Harmonium is an example is ________
Answer» a STRINGED instrument a WIND instrument a PERCUSSION instrument None of these Answer :B

Discussion

19.	Poker is used to make the surface of a metal smoother.
Answer» Solution : Pokers is USED to MAKE holes in the METAL ORDS or stripts.

Discussion

20.	Mass is measured by using a______.
Answer» SPRING balance physical balance measuring jar metre scale Answer :B

Discussion

21.	__________ is used to level the surface of the soil
Answer» Solution :Leveller is USED to level the SURFACE of the SOIL

Discussion

22.	When a neutral body is brought closer to a negatively charged body, then
Answer» it becomes positively charged. the net CHARGE on it is zero it consists of equal positive and negativecharge. Both (a) and (C ). SOLUTION :When a neutral body(i.e., a body which possesses equal positive and netative charge) is brought CLOSER to a negativelycharged body acquires a positive charge and the opposite end (farther end) acquires the negativecharge, but the net charge pres-ent in the body is zero, i.e., still the body will be neutral.

Discussion

23.	When two tunning forks A and B, having frequencies 512 Hz and 212 Hz, respectively, are vibrated simultaneously, the pitch of sound produced
Answer» by 'A' will be more. by 'B' will be more. by A and B will be equal. Cannot be determined Solution :The frequency of vibration determines the shrillness or pitch of any sound. If the frequency of vibration is LOW, we say that the sound has low pitch. If the frequency of vibration is HIGH, we say that the sound has a high pitch. In the given QUESTION TURNING fork A has more frequency, and hence, the pitch of sound produced by A will be more.

Discussion

24.	Find the amount ofheat energy produced by 150 g of a fuel of calorific value 8000 cal g^(-1)
Answer» SOLUTION :`Q=CM=8000xx150=12x15^(5) CAL`

Discussion

25.	1 kilogram is equal to _____.
Answer» 1000 gram 100 gram 1000 milligram 100 milligram Answer :A

Discussion

26.	There are two screws in a vice
Answer» SOLUTION :Two types of scresw are therein a VICE ONE is USED to fix the vice of table and anotherone is used to move the movable JAW.

Discussion

27.	Explain why a clinical thermometer is exclusively used to measure the human body temperature and a laboratory thermometer is used to measure the temperatures of different substances but not to measure the human body temperature .
Answer» Solution :The clinical thermometer is designed to measure the temperature of the human body only .The temperature of human body normally does not go below `35^(@)C and above 42^(@)C` .It means that the range is from `35^(@)C` to `42^(@)C`so it is not USED for measuring the temperature of any OBJECT other than human body laboratory thermomter is generally form `-10^(@)C` to `110^(@)C` and VALUE of each small division is `1^(@)C` Thus small VARIATION in body temperature cannot be measured accurately by using a laboratory thermometer .So we cannot use this thermometer to find out the temperature of the human body. Also in clinical thermometer there is kink which can hold the temperature for long so that one can take out from mouth and see the temperature.

Discussion

28.	Give an example of a motion which is rotatory as well as periodic.
Answer»

Discussion

29.	Is it possible to raise the temperature of water by heating it in a container made up of paper ? [Temperature required to burnthe paper is more than 100^(@)C]
Answer» Solution :Yes it is possible to a raise the TEMPERTURE of water by lacling it in a paper container .The temperture required to burn the paper is more than `100^(@)C` .Asthe paper and the water is in THERMAL contct the temperature of both water and the paper remains the same and the heat supplied to the paper container is ALSO absorbed bvy the water PRESENT in it

Discussion

30.	To prevent tools from __________ oil is applied
Answer» Solution :TOOLS madeof METAL should be CLEANED and oiled to PREVENT from rusting

Discussion

31.	_________ can be used to remove nails from a wall or a pice of wool
Answer» ANSWER :A HAMMER with a FORK

Discussion

32.	A current carrying conductor produces "______"
Answer» only feat only MEGNETIC field Both HEAT and MAGNETIC field None of the above Answer :C

Discussion

33.	Two beaker A and B contain water at different temperatures .When 1 liter of water from beaker A is mixed with 2 litre of water from beaker B the equilibrium temperature is 16^(@)C and when 2 litre of water from beaker A then the equilibrium temperature is 14^(@)C .Determine the tempreature of water in the beaker A and B
Answer» SOLUTION :Heat lost =Heat gained When 1 litre of water fromA is mixed with2 litres of water FORM B then the EQUILIBRIUM temperature attained is `16^(@)C` `Q=mstraiangelt` Let `t_(A)=2xxsxx(t_(B)-16)` `(16-t_(A))=2(t_(B)-16)` `2t_(B)+t_(A)=18-(1)` When 2 litres of water from A is mixed with 2 liters of water from B then the equilibrium temperture of the mixtrue is `41^(@)C` `2xxSxx(14-t_(A))=2xxSxx(t_(B)-14)` `(14-t_(A))=(t_(B)-14)` `t_(B)+t_(A)=28-(2)` `2t_(B)+2t_(A)=56-(3)` `(3)-(1)rarrt_(A)=8^(@)C` `(t_(B))+(T_(A))=28` `t_(B)=28-t_(A)=28-8-20^(@)C`

Discussion

34.	Tools can not reduce the ________ done by the effort.
Answer» ANSWER :WORK

Discussion

35.	India recorded its highest temperature of 51^@C in the town of Phalodi, Rajasthan. Covert into degree Farenheit.
Answer» SOLUTION :`123.8^@ F`

Discussion

36.	Wavelength is measured in :
Answer» kg second litre metre Answer :D

Discussion

37.	Change in temperature of a body is 57^(@)C . The equivalent change in temperature in kelvin scale is ________.
Answer» SOLUTION :CHANGE in TEMPERATURE in KELVIN scale is equal to the change in temperature in celsius scale . Change in temperature =`576^(@)C`-57 k.

Discussion

38.	In a thermos flask the loss of heat energy due to the following methods is minimized
Answer» conduction convection radiation all the above Solution :In a THERMOS FLASKS the LOSS of heat energy is minimized due to conduction convection and radiation

Discussion

39.	In a 100 m race, A touches the finishing line in 10.5 second and B touches it in 11 second. Who is faster, A or B ?
Answer»

Discussion

40.	When the physis teacher has given a task to determine the focal length of a concave mirror a clever boy inthe class focussed the mirror to a distant object. He moved the screen in fornt of the mirror and caught a real image on a screen at a distance of 20 cm from the mirror and he determined the focal length. Where should the object be place so that the object and the image are formed at the same position?
Answer» SOLUTION :The light rays coming from an OBJECT at INFINITY after reflection focus at the principal focus. Hence, FOCAL length f=20cm The image is FORMED at the same position as that of the object, when the object is placed at the centre of curvature. `:.` Radius of curvature `=2f=2xx20=40m`

Discussion

41.	The switch should not be touched with wet hands.
Answer» ANSWER :TRUE

Discussion

42.	The velocity of sound in air, in water and in a given solid is, 330 ms^(-1), 1350 ms^(-1) and 1500 ms^(-1), respectively. If a vibrating tuning fork of frequency 150 Hz is placed in each of these media, then find the distance covered by the sound in air, water and solid, respectively, at the end of 50 vibrations.
Answer» Solution :Speed of sound in air `= 330 ms^(-1)`. Speed of sound in water `= 1350 ms^(-1)`. Speed of sound in solid `1500 ms^(-1)`. Frequency of TURNING fork, (n) = 150 Hz. i.e., it performs 150 vibrations in 1 second. `therefore` The TIME taken by the tuning fork to COMPLETE 50 vibrations `= 1/3 s`. The distance travelled by sound in THREE media in 1 second is 330 m, 1350 m, 1500 m. `therefore` The distance covered by sound in the three given media in 1/3 s is `330 xx 1/3 = 110 m` in air. `1350 xx 1/3 = 450 m` in water. `1500 xx 1/3 = 500 m` in solid.

Discussion

43.	The length of a sconds pendulum is double. What happens to the time period of the pendulum?
Answer»

Discussion

44.	When we rub our hands Which of the following is True ?
Answer» kinetic ENERGY changes into POTENTIAL energy MECHANICAL energy changes into HEAT energy. potential energy changes into kinetic energy. heat energy changes into mechanical energy. Answer :B

Discussion

45.	Tools help us d do work with less _________
Answer» ANSWER :EFFORT

Discussion

46.	Arrange the following steps in a sequential order to explain the formation of conventional currents through ventilation. (a)the cold air enters into the room through windows from high pressure to low pressure region (b) hot air in the room is less denser and it raises up (c ) the rooms are provided with ventilators at the top (d) hot air passes out through the ventilators it creates low pressure region inthe room
Answer» cadb cdab badc cbda Answer :d

Discussion

47.	Match the following columns :
Answer» Solution :(a)-(iv), (B)-(i), (c)-(V), (d)-(II), (E)-(III)

Discussion

48.	The image of the right hand in a plane mirror looks like that of a left hand.
Answer» ANSWER :T

Discussion

49.	Solve the following example : A body of volume 100 cm^3 is immersed completely in water. Find the weight of the water displaced by the body. [g = 9.8 m//s^2, rho(water) = 10^3 kg//m^3]
Answer» Solution :Mass of the metallic rod = 100 g Volume of the metallic rod + volume of wooden block = 400 ml Density of the metallic rod = 5 g `cm^(-3)` Volume of the metallic rod =` MASSOF the metallic rod/density of the rod`=`8/1=n^(3)/1,n^(3)=8, n=2` Volume of wooden the block = `400-20 = 380 cm^(3)` Mass FO the wooden block =`"mass"/"volume"=300/380=0.79" g "cm^(-3)`

Discussion

50.	When an object is held between pole and focus of a concave mirror, the image formed is.
Answer» Solution :If the object is PLACED between F and C of a concave MIRROR, the image is FORMED beyond the C but not at INFINITE distance.

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

Answer the following question What is the principle of thermometer?

______is the force with which the earth pulls a body towards its centre.

on heating substance of the following physical quantities change(s)?

Geometric centere of a mirror is called _______ mirror.

Oli paper is an example of _____ medium of light.

For each of theequation four choices have been provided .select the correct alternative A thermometer workd on the principal of

Fill in the blanks The temperature at which a liquid convert to gaseous state is called ________ of a liquid.

When the Earth comes into the umbra and penumbra of the Moon, _____ is formed.

The density of gold is 19g//cm^(3) find the volume of 38 g

For each of theequation four choices have been provided .select the correct alternative Bimetallic strip works on the principal of ______

Choose the correct statement from the following.

One wants to see a magnified image of an object in a mirror. What type of mirror should one use ?

Mention the different units of time and speed.

Electricity can flow through :

In an electric fan, electrical energy changes into mechanical energy. True/False.

1 kHz = __________ Hz.

Harmonium is an example is ________

Poker is used to make the surface of a metal smoother.

Mass is measured by using a______.

__________ is used to level the surface of the soil

When a neutral body is brought closer to a negatively charged body, then

When two tunning forks A and B, having frequencies 512 Hz and 212 Hz, respectively, are vibrated simultaneously, the pitch of sound produced

Find the amount ofheat energy produced by 150 g of a fuel of calorific value 8000 cal g^(-1)

1 kilogram is equal to _____.

There are two screws in a vice

Explain why a clinical thermometer is exclusively used to measure the human body temperature and a laboratory thermometer is used to measure the temperatures of different substances but not to measure the human body temperature .

Give an example of a motion which is rotatory as well as periodic.

Is it possible to raise the temperature of water by heating it in a container made up of paper ? [Temperature required to burnthe paper is more than 100^(@)C]

To prevent tools from __________ oil is applied

_________ can be used to remove nails from a wall or a pice of wool

A current carrying conductor produces "______"

Tools can not reduce the ________ done by the effort.

India recorded its highest temperature of 51^@C in the town of Phalodi, Rajasthan. Covert into degree Farenheit.

Wavelength is measured in :

Change in temperature of a body is 57^(@)C . The equivalent change in temperature in kelvin scale is ________.

In a thermos flask the loss of heat energy due to the following methods is minimized

In a 100 m race, A touches the finishing line in 10.5 second and B touches it in 11 second. Who is faster, A or B ?

The switch should not be touched with wet hands.

The length of a sconds pendulum is double. What happens to the time period of the pendulum?

When we rub our hands Which of the following is True ?

Tools help us d do work with less _________

Match the following columns :

The image of the right hand in a plane mirror looks like that of a left hand.

Solve the following example : A body of volume 100 cm^3 is immersed completely in water. Find the weight of the water displaced by the body. [g = 9.8 m//s^2, rho(water) = 10^3 kg//m^3]

When an object is held between pole and focus of a concave mirror, the image formed is.