821 + Interview Questions in Physics in Class 7

1.	A cyclist travels a distance of 1 km in the first hour, 0.5 km in the second hour and 0.3 km in the third hour. Find the average speed of the cyclist in ms^(-1) .
Answer» SOLUTION :`0.167 MS^(-1)`

Discussion

2.	A cyclist travels a distance of 1 km in the first hour, 0.5 km in the second hour and 0.3 km in the third hour. Find the average speed of the cyclist in km h^(-1) .
Answer» SOLUTION :`0.6 KM H^(-1)`

Discussion

3.	The energy of flowing water can be converted into electric energy (electricity). True/False.
Answer» ANSWER :T

Discussion

4.	Mass of a stone is 50g. When it is immersed in water the level rises from 45mL to 75mL. Determine the density of the stone.
Answer» Solution :Mass of the STONE =50g VOLUME = `75 - 45 = 30 ML = 30 CM^(3)` Density = `50//30 = 1.6 g//cm^(3)`

Discussion

5.	In a race, two athless A and B reach the finishing point in 20 second and 22 second, respectively. (a) What is the ratio of their speeds ? (b) if both are allowed to run with their respective speeds for a given time, what is the ratio of the distance covered by them gt
Answer»

Discussion

6.	{:(,"Column A",,"Column B"),("(A)","Measuring cylinder","(a)","kgf, gf"),("(B)","Gavitational units of weight","(b)","ml of cc"),("(C)","1 g "cm^(-3) ,"(c)","Zero weight"),("(D)","Zero gravitational force","(d)",1000" kg "m^(-3)):}
Answer» (a)` Atob, Btoa, CTOD, Dtoc.` (b) `Atob,Btod, Ctoa, Dtoc,` (c ) `Atoc,Btod, Ctob,Dtoa` (d) `Atoa, Btoc,Ctob, Dtod` Solution :A-b ""A measuring CYLINDER is used to measure the VOLUME of liquids in millitres or cubic centimetres. B-a ""GRAVITATIONAL units of weight are kgf and gf.,brgt C-d ""The units of density are " g " `cm^(-3)` , " kg " `m^(-3)` They are related are " g " `cm^(-3)` = 1000 " kg "`m^(-3)`,brgt D-c "" If the gravitational force acting on a body is zero, then the weight of the body is SAID to be zero.

Discussion

7.	The property due to which a light ray striking a surface is returned back into the same medium is called
Answer» REFRACTION REFLEX action reflection REGRESSION ANSWER :C

Discussion

8.	Real image is formed by a ______ mirror.
Answer» ANSWER :CONCAVE

Discussion

9.	Arrange the following steps in sequential order to find the depth of the ocean bed using Sonar. (A) The time taken (t) to receive the sound is measured. (B) Ultrasonic sound is sent to the ocean bed whose depth (d) is to be found from the transmitter attached to the ship. (C) If 'v' is the velocity of sound in water, the depth can be found using, v = 2d/t. (D) The ultrasonic sound reflected form the ocean bed is received by a suitable detector in the ship.
Answer» ABCD ADCB BADC BDAC Solution :ULTRASONIC sound is sent to the ocean bed whose depth (d) is to be found from the transmitter ATTACHED to the ship. (II) The ultrasonic sound reflected from the ocean bed is received by a suitable detector in the ship. (iii) The TIME taken (t) to receive the sound is measured. (iv) If 'v' is the velocity of sound in water, the depth can be found using, `v = (2d)/(t)`.

Discussion

10.	Name the device that can be used to detect the presence of current in a circuit
Answer» MAGNETIC compasss cell an inverter voltmeter Answer :A

Discussion

11.	Assertion (A): Clinical thermometer cannot be used to meaure the temperature of melting ice Reason (R ): The range of clinical thermometer is from 35^(@)C to 43^(@)C
Answer» both a and r are CORRECT and r is the correct explanation of a both a and r are correct but RA is not the correct explanation of a a is correct and r is INCORRECT both a and r are incorrect Solution :The rangeof clinical thermometer is form `35^(@)C` to `43^(@)C` but the temperture of melting ice is `0^(@)C` so the clinicall thermometer cannot be used to measure the TEMPERATURE of melting ice so A and R are correct and R is the correct explanation of A.

Discussion

12.	Rajesh took two identical glasses containing the same amount of hot milk at the same temperature He kept one glass undisturbed .While the other one he continously stirred using a spoon .Then among them milk in which glass cools faster ? Why?
Answer» Solution :The milk in GLASS which is stirred by a SPOON COOLS first because when we stir using a spoon it will increase the movement of molecules the cold molecules on the SURFACE will settle at the bottom and hot molecules form bottom reach the top .Thus stirrring increase the HEAT transfer rate by convection

Discussion

13.	The number of image of an object placed between two plane parallel mirrors is _____
Answer» two one infinite Cannot be determined. Solution :When two MIRROR are placed PARALLEL to each other. The image of an object formed by one mirror acts like virual object for ANOTHER mirror, and its VIRTUAL image acts like virtual object for previous one and this process continues and an infinite number of images are formed by the two mirrors. (or) `n=(360)/(theta)-1` `theta=0^(@)` `impliesn=(360)/(0)-1` `n=oo-1=oo="infinite"`

Discussion

14.	Choose the correct statement: (a) During boiling a liquid change in to gaseous state at constant temperaute with absorption of heat energy (b) During solidification a liquid changes in to solid state at constant temperature with release of heat energy
Answer» only a only B both a and b NONE of these Solution :Both the GIVEN STATEMENT aretrue

Discussion

15.	When a ray of light passes through glass slab, refraction of light occurs___
Answer» the DEVIATION of RED light is maximum. the deviation of violet light is maximum. the deviation of BLUE light is maximum. all RAYS DEVIATE equally. Answer :B

Discussion

16.	The temperature of pure melting ice is :
Answer» `0^@C` `100^@C` `95^@C` `98.6^@F` Answer :A

Discussion

17.	Arrange the following steps in sequential order to demonstrate the magnetic effect of the elctric cur-rent using magnetic compass. (A) Wind an insulated conducting wire around the magnetic compass such that the axis of the coil is directed along east west direction and con-nect the free ends of the wire to a cell through a switch. (B) Take a magnetic compass. (C ) When current flows through the conducting wire, it behaves as a magnet and deflects the compass needle. (D) When the switch is closed, the magnetic nee-dle in the compass deflects from its initial posi-tion and when the switch is opend, the needle comes back to its initial position.
Answer» BADC CBAD ACBD ABCD Solution :(i) Take a magnetic compass. (ii)Wind an insulated CONDUCTING wire aroundthe magnetic compass such that the axis of the coil is directed along east-west directionand con-nect the free ends of the wire to a cell through a switch. (iii) When the switch is CLOSED, the magnetic nec-dle in the compass deflects from its initial posit-tion and when the switch is OPENED, the needle comes back to its initial position. (iv) When CURRENT flows through the conducting wire, it hehavesas a magnet and deflects the compass needle.

Discussion

18.	Consider the following linear equationsax+ by+cz=0,bx+ cy+az=0,cx+ ay+bz=0.Match the statement in Column I with the properties in Column IIand indicate your answer by darkening the appropriate bubbles in the 4 xx 4 matrix given in the ORS.
Answer» Oboes Veena Mridangam Violin Solution :Oboes is an EXAMPLE of WIND instrument and musical sound is produced from it by VIBRATING AIR column in the tube by BLOWING air into it.

Discussion

19.	Why do we use a sharp contiuous metla blade for cutting a mango and a blade with many small teethfo cutting metals ?
Answer» Solution : The SHARP teeth concentrate all the force onto a very small area, resulting in a high pressure which allows it to penterate, into the WORK piece. Mango is a soft material. So, for CUTTING it, we requireonly small effort. Therefore, we use a continuous POINTED edge knife.

Discussion

20.	Why does a black smith heat the iron block before hammering it to change its shape?
Answer» SOLUTION :When an IRON BLOCK is heated the molecules try to move apart and the FORCE of atrraction between the molecules reduce . So we can easily change dimensions of the iron block

Discussion

21.	Which of the following is not a consumer of electrical energy ?
Answer» A GENERATOR An ELECTRIC motor An electromagnet A bulb Solution :A generator is not a CONSUMER of ELECTRICAL ENERGY.

Discussion

22.	Assertion (A) : All the bulbs connected in parallel glow brightly. Reason (R) : All the bulbs are connected directly to a battery and derive the required electrcial energy.
Answer» Both A and R are TRUE and R is the correct EXPLANATION of A. Both A and R are true and R is not the correct explanation of A. A is true but R is false. Both A and R are false. Solution :All the bulb connectedin parallel glow brightly because all the BULBS are CONNECTED DIRECTLY to a bat-tery, and derive the required electrical energy.

Discussion

23.	What are the factors affecting the heat lost or gained by abody?
Answer»

Discussion

24.	A boy fires a gun and another boy at a distance of 1020 m hears the sound of firing the gun 3 s after seeing its smoke. Find the speed of sound.
Answer» SOLUTION :`340MS^(-1)`

Discussion

25.	A harrow can be used to elvel the wet field before transplanation
Answer» Solution :The harrow is USED to REMOVE weeds in a field. This is also used to LEVEL the wet field before transplantion

Discussion

26.	What is the number of images of an object held between two parallel plane mirrors ?
Answer» TWO one infinite Cannot be determined. Solution :When two mirror are placed PARALLEL to each other the image of an object formed by one mirror ACTS, LIKE virtual object for another mirror, and its virtual image acts, like virtual object for previous one and this process CONTINUES and an infinite number of imageare formed by the two mirrors. (or) `n=(360)/(theta)-1` `theta=0` `impliesn=(360)/(0)-1` `n=oo-1=oo="infinite"`

Discussion

27.	Fog is formed on the bathroom mirror when one takes a hot shower but does not during cold shower because
Answer» evaporatiion of WATER is more at higher temperature FORMATION of FOG on the mirror does not depent on amount of vapour formation of fog on mirror isnot concerned with temperature of water both a and b SOLUTION :Fog formed on the bathroom mirror when we TAKEN a hotshower .Because the evaporationof water molecules is more at higher temperture

Discussion

28.	The bulbs in houses are connected in
Answer» parallel combination series combination series and parallel. neither in series nor in parallel. Solution :Generally the bulbs or electrical appliances of house hold are CONNECTED in parallel combination.It is to avoid the INTERRUPTION of power for the GLOW (work-ing) of BULB (appliance) when any of the electrical appliance (bulb) gets damaged.

Discussion

29.	Volume of an irregular shaped solid can be measured by using a____
Answer» DENSITY bottle spring balance measuring cylinder physical balance Answer :C

Discussion

30.	.......... determines the degree of hotness or coldness of a body.
Answer» SOLUTION :TEMPERATURE

Discussion

31.	The sounds of frequencies greater than _____ are called ultrasonic sounds.
Answer» ANSWER :B

Discussion

32.	{:(,"Column A",,, "Column B"),(A., "Height of the cloud", (), a., "Gunny bags"),(B.,"Frequency, " n = 10 Hz, ( ), b., "Painful to humans"),(C., "Sound absorption", ( ), c., "Time Period " T = 0.1s),(D., "More than " 90 dB, ( ), d., "Speed of sound " xx " time interval"),(E., "Syrinx", (), e., "Ring of cartilage"):}
Answer» `A to B, B to c, C to d, D to e, E to a` `A to e, B to c, C to d, D to a, E to b` `A to a, B to c, C to e, D to b, E to d` `A to d, B to c, C to a, D to b, E to e` Solution :`{:(A - d,, "Speed of the SOUND " = ("Height of the cloud")/("time taken")),(B - c,, n = 1/T", " " If " n = 10 Hz","),(,, rArr T = 1/n = 1/10 = 0.1 s),(C - a,, "Sound energy is absorbed by SOFT materials, like gunny bags, carpets, etc."),(D - b,, "The sound of loudness more than 90 DB is painful to humans."),(E - e,, "Birds produce sound with the help of cartilage called syrinx."):}`

Discussion

33.	If the screw of a vice is rotated in the clockwise direction, then _________
Answer» JAWS MOVE closer jaswsmoves away TOOL rotates in closkwise DIRECTION tool rotates in anti-clockwise direction ANSWER :A

Discussion

34.	Fill in the blanks Substance through which heat travels easily and quickly are said to be _________of heat.
Answer» ANSWER :GOOD CONDUCTORS

Discussion

35.	Cooking gas converts .................. energy into heat energy
Answer» SOLUTION :CHEMICAL

Discussion

36.	The loudness of sound is measured in _______.
Answer» seconds metre DECIBELS hertz Solution :The LOUDNESS of SOUND is MEASURED in decibels (DB).

Discussion

37.	"_______" and "_______" are two defects of voltaic cell.
Answer» ANSWER :POLARIZATION, LOCAL ACTION

Discussion

38.	Velocity of sound is minimum in ______
Answer» WOOD vacuum water air Answer :B

Discussion

39.	Read the following statements and choose the correct option. Planets are not luminous bodies. The sun is the nearest star to us from which the earth recives most of the light.
Answer» Only A is true Only B is true Both A and B are true Both A and B are false Solution :Planets are not luminou, the SUN is the NEAREST STAR to our planet (earth) from which it RECEIVES most of the light.

Discussion

40.	What is the function of thermos flask how does it reduce heat loss?
Answer»

Discussion

41.	The principle of reflection of sound is used ________
Answer» in hearing echos to locate shoals of FISH under the sea bed in the DETECTION of INSECTS by bats All the above Answer :D

Discussion

42.	The instruments made of long and hollow pipes with a certain number of holes on the sides are
Answer» wind or reed INSTRUMENTS. stringed instruments. drum instruments. All the above Solution :Wind or reed instruments are made of LONG and HOLLOW pipes with a CERTAIN number of HOLES on the sides.

Discussion

43.	Assertion (A): Different musical sounds are produced from percussioninstruments by exciting the stretched membrane at different tensions. Reason (R): Flute, bassoon, oboes are examples of drum instruments.
Answer» Both A and R are correct 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 :Different musical SOUNDS can be produced by exciting the stretched MEMBRANES at different TENSIONS of percussion instruments and TABLA, mridangam, drums, ETC., are some of the examples.

Discussion

44.	If the angle of incidence on a plane mirror is 30^(@), then angle between the reflected ray and the plane mirror is _____
Answer» Solution :If the angle of incidence is `30^(@)`, the angle of REFLECTION is also `30^(@)`. The angle between the NORMAL line and plane MIRROR is `90^(@)`. So, the angle between REFLECTED RAY and the plane mirror is `90^(@)-30^(@)=60^(@)`.

Discussion

45.	Energy possessed by a compressed spring is....... energy.
Answer» SOLUTION :POTENTIAL

Discussion

46.	Gourang made an electric circuit with three bulbs B_(1), B_(2) and B_(3) a cell and two switches S_(1) and S_(2) as shown in figure. He notes his observation when (a) S_(1) is closed and S_(2) is open, (b) S_(2) is closed and S_(1) is open. He also found that a bulb whose failure made the circuit 'open' irrespective of the status of S_(1) and S_(2) . What are his observation.
Answer» SOLUTION :(a) If `S_(1)` is CLOSED and `S_(2)` is open, only `B_(1)` and `B_(2)` glow. (b) If `S_(2)` is closed and `S_(1)` is open, only `B_(1)` and `B_(3)` glow. If `B_(1)` fails the CIRCUIT becomes open, even ifboth `S_(1)` and `S_(2)` are closed.

Discussion

47.	Read the following statements and choose the correct option. (A) Planets are not luminous bodies. (B) The sun is the nearest star to us from which the earth receives most of the light.
Answer» Only A is true Only B is true Both A and B are true Both AAND B are false Answer :C

Discussion

48.	A boy starts from home, goes to a shop, which is 2 km away, buys things, and comes back in an hour. What is the speed with which he travels?
Answer» SOLUTION :Distance covered by the boy from his home to the shop = 2 km = Distance covered while coming back home = 2km So, the total distance covered by the boy = 2 + 2 = 4 km Time taken = 1 HOUR Speed = Distance travelled/time taken = `4//1=4km//h`

Discussion

49.	A mercury thermometer makes use of the property of expansion of liquids on heating.
Answer» ANSWER :T

Discussion

50.	What are the different points one must keep in mind while choosing a suitable scale for drawing a ghaph? Discuss.
Answer»

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

A cyclist travels a distance of 1 km in the first hour, 0.5 km in the second hour and 0.3 km in the third hour. Find the average speed of the cyclist in ms^(-1) .

A cyclist travels a distance of 1 km in the first hour, 0.5 km in the second hour and 0.3 km in the third hour. Find the average speed of the cyclist in km h^(-1) .

The energy of flowing water can be converted into electric energy (electricity). True/False.

Mass of a stone is 50g. When it is immersed in water the level rises from 45mL to 75mL. Determine the density of the stone.

In a race, two athless A and B reach the finishing point in 20 second and 22 second, respectively. (a) What is the ratio of their speeds ? (b) if both are allowed to run with their respective speeds for a given time, what is the ratio of the distance covered by them gt

{:(,"Column A",,"Column B"),("(A)","Measuring cylinder","(a)","kgf, gf"),("(B)","Gavitational units of weight","(b)","ml of cc"),("(C)","1 g "cm^(-3) ,"(c)","Zero weight"),("(D)","Zero gravitational force","(d)",1000" kg "m^(-3)):}

The property due to which a light ray striking a surface is returned back into the same medium is called

Real image is formed by a ______ mirror.

Name the device that can be used to detect the presence of current in a circuit

Assertion (A): Clinical thermometer cannot be used to meaure the temperature of melting ice Reason (R ): The range of clinical thermometer is from 35^(@)C to 43^(@)C

Rajesh took two identical glasses containing the same amount of hot milk at the same temperature He kept one glass undisturbed .While the other one he continously stirred using a spoon .Then among them milk in which glass cools faster ? Why?

The number of image of an object placed between two plane parallel mirrors is _____

Choose the correct statement: (a) During boiling a liquid change in to gaseous state at constant temperaute with absorption of heat energy (b) During solidification a liquid changes in to solid state at constant temperature with release of heat energy

When a ray of light passes through glass slab, refraction of light occurs___

The temperature of pure melting ice is :

Consider the following linear equationsax+ by+cz=0,bx+ cy+az=0,cx+ ay+bz=0.Match the statement in Column I with the properties in Column IIand indicate your answer by darkening the appropriate bubbles in the 4 xx 4 matrix given in the ORS.

Why do we use a sharp contiuous metla blade for cutting a mango and a blade with many small teethfo cutting metals ?

Why does a black smith heat the iron block before hammering it to change its shape?

Which of the following is not a consumer of electrical energy ?

Assertion (A) : All the bulbs connected in parallel glow brightly. Reason (R) : All the bulbs are connected directly to a battery and derive the required electrcial energy.

What are the factors affecting the heat lost or gained by abody?

A boy fires a gun and another boy at a distance of 1020 m hears the sound of firing the gun 3 s after seeing its smoke. Find the speed of sound.

A harrow can be used to elvel the wet field before transplanation

What is the number of images of an object held between two parallel plane mirrors ?

Fog is formed on the bathroom mirror when one takes a hot shower but does not during cold shower because

The bulbs in houses are connected in

Volume of an irregular shaped solid can be measured by using a____

.......... determines the degree of hotness or coldness of a body.

The sounds of frequencies greater than _____ are called ultrasonic sounds.

If the screw of a vice is rotated in the clockwise direction, then _________

Fill in the blanks Substance through which heat travels easily and quickly are said to be _________of heat.

Cooking gas converts .................. energy into heat energy

The loudness of sound is measured in _______.

"_______" and "_______" are two defects of voltaic cell.

Velocity of sound is minimum in ______

Read the following statements and choose the correct option. Planets are not luminous bodies. The sun is the nearest star to us from which the earth recives most of the light.

What is the function of thermos flask how does it reduce heat loss?

The principle of reflection of sound is used ________

The instruments made of long and hollow pipes with a certain number of holes on the sides are

Assertion (A): Different musical sounds are produced from percussioninstruments by exciting the stretched membrane at different tensions. Reason (R): Flute, bassoon, oboes are examples of drum instruments.

If the angle of incidence on a plane mirror is 30^(@), then angle between the reflected ray and the plane mirror is _____

Energy possessed by a compressed spring is....... energy.

Read the following statements and choose the correct option. (A) Planets are not luminous bodies. (B) The sun is the nearest star to us from which the earth receives most of the light.

A boy starts from home, goes to a shop, which is 2 km away, buys things, and comes back in an hour. What is the speed with which he travels?

A mercury thermometer makes use of the property of expansion of liquids on heating.

What are the different points one must keep in mind while choosing a suitable scale for drawing a ghaph? Discuss.

"_" and "_" are two defects of voltaic cell.