821 + Interview Questions in Physics in Class 7

1.	A car travels with speed 30 km h^(-1)for 30 minutes and then with speed 40 km h^(-1) for one hour. Find the average speed of car
Answer» SOLUTION :`36.6 67 KM H^(-1)`

Discussion

2.	kg" "1^(-1) is a unit of density.
Answer» SOLUTION :KG `1^(-1)` is a UNIT of DENSITY

Discussion

3.	To break the mud rocks on the surface of the soil, _________ can be used
Answer» horrow seed drill leveller wooden plank Answer :D

Discussion

4.	Write the following statements in a sequential order to find the depth of the ocean bed by the using sonar . (A) The depth of the ocean bed can be found by d = (vt)/(2). (B) At the bottom of a ship two devices , one is transmitter which products ultrasonics and a receiver for the detection of the reflected ultrasonics from the ocean bed are fixed . (C) The velocity fo ultrasonics in ocean water is 'v' and the time taken to receive the reflected ultrasonics from the ocean bed be 'f'. (D) If the depth of ocean bed is 'd' , then v = (d + d)/(t) = (2d)/(t).
Answer» a b C d b a c d d a c b c b a d Solution :From the given data, collect the total time taken, t = 4 s. The distance travelled by sound `= 2 XX` (depth of the ocean bed). Speed `= (2d)/(t) to (a)` `d = (1500 xx t)/(2) = (1500 xx 4)/(2) = 3000 m = 3 km` So, the depth of the ocean bed, (d) = 3 km.

Discussion

5.	The diameter fo ametallic plate can be measured by using a divider
Answer» SOLUTION :We can measure the DIAMETER of metallic PALTE by using a divider

Discussion

6.	Can virtual image be formed on the retina in a seeing process?
Answer» SOLUTION :Vritual IMAGE are FORMED by diveragent BEAM of LIGHT.

Discussion

7.	In general, the voice of a woman has a higher frequency than that of a man.
Answer» 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 CASE of WOMEN, the sound produced is high pitched. So, voice of women has a higher frequency than that of MEN.

Discussion

8.	Which of the following is required to cut metal pipes by fixing is to a vice?
Answer» Table Drill bit Cutting plier Hammer Answer :A

Discussion

9.	When can be speed and average speed of a vehicle be equal ?
Answer»

Discussion

10.	The energy possessed by a body due to its position is called ......... energy
Answer» SOLUTION :POTENTIAL

Discussion

11.	{:(,"Column A",,, "Column B"),(A., "Compressions and rarefactions", (), a., "Birds"),(B., "Syrinx", ( ), b., "Sound wave"),(C., "Internal organs", ( ), c., "Noise"),(D., "Sound of thunder", ( ), d., "Surface area of vibrating body"),(E., "Intensity", (), e., "Ultrasonic sounds"):}
Answer» Solution :A - B `" "` Sound wave propagates in the FORM of compressions and rarefactions. B - a `" "` Birds produce sound with the help of a ring of cartilage called syrinx. C - E `" "` Ultrasonic sound is used for IMAGING the internal organs of a human body. D - c `" "` The sound of thunder produces noise. E - d `" "` INTENSITY of sound depends on the surface area of the vibrating body.

Discussion

12.	Assertion (A): Photosynthesis takes place only during the day. Reason: (R): Light energy is required for the process of photosynthesis.
Answer» Both A and R are correct and R is not 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 :Light ENERGY is REQUIRED for the process of photosynthesis. The light energy is CONVERTED into chemical energy with the HELP of chlorophyll present in the leaves of plants. So, A and R are correct and R is the correct explanation of A.

Discussion

13.	Three persons P_(1), P_(2) and P_(3) are at different points A, B and C,as shown in the figure.P_(1) and P_(2) clap at the same time.For P_(3) to hear two distinct claps, the minimum distance betweenl P_(1) and P_(2) should be ______ m. (The velocity of sound in air is 330 ms^(-1))
Answer» 33 330 363 660 Solution :Human ear can hear two sounds separately only if they reach the ear after an INTERVAL of 1/10 of a second. So, the time taken by the sound from `P_(1)` to `P_(2)` should be GREATER than `1//10 s = 0.1 s.` The distance between `P_(1)` and `P_(2)` `= v XX t = 330 xx 0.1 = 33 m.`

Discussion

14.	Fill in the blanks _________is the SI unit of heat
Answer» ANSWER :JOULE

Discussion

15.	What is the use of spring in a tin cutter?
Answer» Solution : A TIN cutter is SIMILAR to pair of scissors, but a strong spring is FIXED between the handle of ONE blade and the other blade. When we cut the METAL by pressing the the spring gets streched, so, energy is stored in the spring. This energy of the spring is used to move the jaw apart after the opreations

Discussion

16.	_________ is uded to make holes in the metal rods
Answer» ANSWER :POKER

Discussion

17.	Fill in the blanks The transfer of heat which takes place due to the vibration of particles is _______.
Answer» ANSWER :more

Discussion

18.	Draw position vs time graph of uniform velocity.
Answer»

Discussion

19.	Answer the following question Define temperature
Answer»

Discussion

20.	For each of theequation four choices have been provided. select the correct alternative Clinical thermometer is calibrated in __________.
Answer» CELSIUS SCALE FAHRENHEIT scale Absoulte scale Both a and b Answer :C

Discussion

21.	Which of the following statement is /are true about electromagnet ?
Answer» It works on the principal of 'magnetic effects of electric current'. Electromagnets are USED in electric bell. Electromagnets are used to LIFT HEAVY loads. All the above. Solution :Electromagnets are used in electric bells and to lift heavy loads and WORK on the principal of magnetic effect of electric current.

Discussion

22.	Slow and fast are relative. Explain it with examples.
Answer»

Discussion

23.	Read the following statements and choose the correct option. (A) Shadows are formed due to rectilinear propagation of lght. (B) When the position of the earth is between sun and moon, lunar eclipse is formed.
Answer» Only A is true Only B is true Both A and B are true Both A and B are false Solution :(i) Light caste shadows of objects in its path due to its RECTILINEAR propagation property. (ii) Lunar eclipes is formed when EARTH COMES between the sum and the MOON.

Discussion

24.	Sulphite is used to
Answer» WORK PIECE TOOL table MEASURING insrument Answer :B

Discussion

25.	An electric generator (Dynamo) converts
Answer» mechanical ENERGY into ELECTRICAL energy. electrical energy into mechanical energy. chemical energy into electrical energy. chemical energy into mechanical energy. Solution :An ELECTRICGENERATOR (dynamo) CONVERTS mechanical energy into ELECTRIC energy.

Discussion

26.	A thermometer uses :
Answer» water mercury air none of the above Answer :B

Discussion

27.	1 watt = ______ lumen.
Answer»

Discussion

28.	A man is standing not exactly at the exactly at the centre, in between two parallel walls separated by a distance 990 m. He fires a gun and hears the first echo after 2 s, the time taken to hear 3rd echo after firing is ______ s. (take velocity of sound in air is 330 ms^(-1))
Answer» 5 7 6 8 Solution :He HEARS the first echo after 2 s. The distance between the 1st WALL and the man is `d = v xx t = 330 xx 1 = 330 m.` So, the distance between the man and 2ND wall is `990 - 330 = 660 m.` So, TIME taken for 2nd echo time `= ("distance")/("velocity") = (2 xx 660)/(330) = 4 s` The 3rd and 4th echo reach at the same time. Time taken for 3rd echo = time taken to hear the first echo + time taken to hear the 3rd echo `= 2 + (2 xx 660)/(330) = 2 + 2 xx 2 = 6 s.`

Discussion

29.	In a torch, the source of electricity is :
Answer» the bulb the switch the CELL the mains Solution :the cell

Discussion

30.	The garvitational force exerted by the sun on the Moon is greater than that exerted by the Earth on the Moon. Why then does not the Moon escape from the Earth, during solar esclipe?
Answer» ANSWER :LUNAR ECLIPSE

Discussion

31.	A torch bulb glows if the terminals of the bulb are connected to the terminals of a cell by the metallic wire.
Answer» ANSWER :TRUE

Discussion

32.	Heat energy is invisible
Answer» SOLUTION :HEAT is an invissible FORM of ENERGY

Discussion

33.	Match the column the entries given in Column A with the appropriate ones in Column B.
Answer» ANSWER :`A:C B: a C:E D:b E: d`

Discussion

34.	When do we say that a pendulum has completed one oscillation ?
Answer»

Discussion

35.	A diminished virtual image can be formed only in
Answer» PLANE mirror concave mirror convex mirror All the above. Answer :B

Discussion

36.	A and B are two identical conducting rods. A is given positive charge and B is connectedto a cell as shown in the figure. Will there be any change in the electrostatic force between A and B if the switch is closed ?
Answer» Solution :There will be no electrostatic FORCE between A and B. When switch is closed, electric current passes through B. The quantity of charge entering B is equal to the quanity of chargeleaving B making it electrically neutral . And as charges in B are in motion, ATTRACTION between A and B of electrostatic INDUCTION is negligible.

Discussion

37.	CONDUCTORS AND INSULATORS
Answer» SOLUTION :NA

Discussion

38.	Which of the folllowing does not have a metal part?
Answer» Hack-saw Wooden plough Tin CUTTER NONE of the above Answer :D

Discussion

39.	If mass of the substacne is 20 g then the heat energy required to melt 1 g of the substacne is _______J
Answer» 300 15 113.5 2270 Solution :The SUBSTANCE melts byabsorbing 340 -40 =300 J of enegy i.e20 G of substacne absrobs `(300)/(20)=15J` of energy and melts without RISE in temperature

Discussion

40.	For a substacne to undergoa change of state heat must be either given to it or taken away from it
Answer» Solution :For a substance to UNDERGO a CHANGE of state heat MUST EITHER be given to it or TAKEN away from it

Discussion

41.	A physics student Ram was given an empty density bottle,a physical balance and a certain liquid. He first found the weight of empty density bottle to a be 50 gf When completely filled with a liquid, it weighs 130 gf. He calculated the density of the liquid. What could be his answer?
Answer» Solution :Mass of the eempty bottle = 50 " g " Mass of water = 100- 50= 50 " g " Mass of the liquid = 130 - 50 = 80 " g " VOLUME of the liquid = 50 " " `cm^(3) LTBR. (` :. Volume of 1 " g " water = 1 ML)` Density of the liquid = `"mass"/"volume" = 80/50 = 1.6 " g " cm^(-3)`.

Discussion

42.	The heating curve of a particular substance in solid state is as shows in thefigure.Choose the correct alternative If mass of the substance is 20 g then the heat energy required to melt 1 g the substacne is ______J.
Answer» 300 15 113,50 2270 Answer :B

Discussion

43.	The sun's rays are falling on two identical ice blocks as shown in the figure Then
Answer» block a starts melting FIRST block B starts melting first both starts melting at thesame time cannot be campared Solution :NORMAL incidence is the condition for maximum absorption of HEAT RADIATION and hence ice block A starts melting first

Discussion

44.	SI unit of volume is cubic metre.
Answer» Solution :SI UNIT of VOLUME is cubic metre.

Discussion

45.	Do all bulbs we use work on the principle of heating effects of electric current ? Discuss.
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

46.	An elephant covers 120 km in 3 hours and a tiger covers 130 km in 2 hours. Which is faster? What is its speed?
Answer» SOLUTION :TIGER is FASTER. SPEED is `65 km//h`

Discussion

47.	The size of an image formed by a plane mirror is _____.
Answer» LARGER than the SIZE of the OBJECT. smaller than the size of the object. equal to the size of the object. Cannot be determined. Answer :C

Discussion

48.	Sound can only be produced by vibrating bodies
Answer» ANSWER :T

Discussion

49.	(a) write the relation between heat capacity and specific heat capacity (b) 7000 J of heat energy is supplied to a copper sphere of mass 90 g what is the raise in temperature of the shere? (Specific heat capacity of copper =0.09 cal g^(1)^.@C^(-1))
Answer»

Discussion

50.	How many images are formed when an object is placed between two mirrors which make an angle of 45^(@) with each other?
Answer» 8 7 2 infinite Solution :The NUMBRE of IMAGES FORMED `(N)=(360)/(theta)-1` `=(360)/(45)-1` =8-1 =7

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

A car travels with speed 30 km h^(-1)for 30 minutes and then with speed 40 km h^(-1) for one hour. Find the average speed of car

kg" "1^(-1) is a unit of density.

To break the mud rocks on the surface of the soil, _________ can be used

The diameter fo ametallic plate can be measured by using a divider

Can virtual image be formed on the retina in a seeing process?

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

Which of the following is required to cut metal pipes by fixing is to a vice?

When can be speed and average speed of a vehicle be equal ?

The energy possessed by a body due to its position is called ......... energy

{:(,"Column A",,, "Column B"),(A., "Compressions and rarefactions", (), a., "Birds"),(B., "Syrinx", ( ), b., "Sound wave"),(C., "Internal organs", ( ), c., "Noise"),(D., "Sound of thunder", ( ), d., "Surface area of vibrating body"),(E., "Intensity", (), e., "Ultrasonic sounds"):}

Assertion (A): Photosynthesis takes place only during the day. Reason: (R): Light energy is required for the process of photosynthesis.

Three persons P_(1), P_(2) and P_(3) are at different points A, B and C,as shown in the figure.P_(1) and P_(2) clap at the same time.For P_(3) to hear two distinct claps, the minimum distance betweenl P_(1) and P_(2) should be ______ m. (The velocity of sound in air is 330 ms^(-1))

Fill in the blanks _________is the SI unit of heat

What is the use of spring in a tin cutter?

_________ is uded to make holes in the metal rods

Fill in the blanks The transfer of heat which takes place due to the vibration of particles is _______.

Draw position vs time graph of uniform velocity.

Answer the following question Define temperature

For each of theequation four choices have been provided. select the correct alternative Clinical thermometer is calibrated in __________.

Which of the following statement is /are true about electromagnet ?

Slow and fast are relative. Explain it with examples.

Read the following statements and choose the correct option. (A) Shadows are formed due to rectilinear propagation of lght. (B) When the position of the earth is between sun and moon, lunar eclipse is formed.

Sulphite is used to

An electric generator (Dynamo) converts

A thermometer uses :

1 watt = ______ lumen.

A man is standing not exactly at the exactly at the centre, in between two parallel walls separated by a distance 990 m. He fires a gun and hears the first echo after 2 s, the time taken to hear 3rd echo after firing is ______ s. (take velocity of sound in air is 330 ms^(-1))

In a torch, the source of electricity is :

The garvitational force exerted by the sun on the Moon is greater than that exerted by the Earth on the Moon. Why then does not the Moon escape from the Earth, during solar esclipe?

A torch bulb glows if the terminals of the bulb are connected to the terminals of a cell by the metallic wire.

Heat energy is invisible

Match the column the entries given in Column A with the appropriate ones in Column B.

When do we say that a pendulum has completed one oscillation ?

A diminished virtual image can be formed only in

A and B are two identical conducting rods. A is given positive charge and B is connectedto a cell as shown in the figure. Will there be any change in the electrostatic force between A and B if the switch is closed ?

CONDUCTORS AND INSULATORS

Which of the folllowing does not have a metal part?

If mass of the substacne is 20 g then the heat energy required to melt 1 g of the substacne is _______J

For a substacne to undergoa change of state heat must be either given to it or taken away from it

A physics student Ram was given an empty density bottle,a physical balance and a certain liquid. He first found the weight of empty density bottle to a be 50 gf When completely filled with a liquid, it weighs 130 gf. He calculated the density of the liquid. What could be his answer?

The heating curve of a particular substance in solid state is as shows in thefigure.Choose the correct alternative If mass of the substance is 20 g then the heat energy required to melt 1 g the substacne is ______J.

The sun's rays are falling on two identical ice blocks as shown in the figure Then

SI unit of volume is cubic metre.

Do all bulbs we use work on the principle of heating effects of electric current ? Discuss.

An elephant covers 120 km in 3 hours and a tiger covers 130 km in 2 hours. Which is faster? What is its speed?

The size of an image formed by a plane mirror is _____.

Sound can only be produced by vibrating bodies

(a) write the relation between heat capacity and specific heat capacity (b) 7000 J of heat energy is supplied to a copper sphere of mass 90 g what is the raise in temperature of the shere? (Specific heat capacity of copper =0.09 cal g^(1)^.@C^(-1))

How many images are formed when an object is placed between two mirrors which make an angle of 45^(@) with each other?