821 + Interview Questions in Physics in Class 7

1.	Explain the anomalous expansions of water with hope's apparatus.
Answer»

Discussion

2.	The mass of a density bottle when it is filled with a liquid of density 3000 kg m^(-3)is 400 g and the mass of the bottle when it is filed with water is 200 g.The mass of the empty density bottlewhen it is filled with water is 200 g.The mass of the empty density bottle is "_____" g.
Answer» 10 100 50 500 Solution : Mass of the EMPTY bottle = `m_(1)` Mass of the bottle with water, `m^(2)` = 200 g Mass of he bottle with liquid, `m_(3)` =400 g DENSITY of the liquid = `3000 " Kg "m_(-3) = 3 " g " CM^(-3)` Density of liquid =`(m_(3)-m_(1))/(m^(2)-m_(1)` `3=(400-m_(1))/(200-m_(1))` `400-m_(1)=600-3m_(1)` `2m_(1)= 200 " g ",m_(1)=100 " g "`.

Discussion

3.	Sandeep constructed a simple pendulum to find the value of 'g' at that place. He observed that the bob of a simple pendulum moves from the mean position to one of the extreme positions in 0.5 s. Using this he determined the (i) time period of the simple pendulum. (ii) number of oscillations the pendulum has under - gone in four seconds and (iii) the frequency of oscillation of the pendulum. What are his answers ?
Answer» Solution :(i) Time period, is the time taken to complete one oscillation. One oscillation is one to and fromotion. Hence, time period `T = 0.5 xx 4 = 2 s.` (II) As per the data given, the pendulum PERFORMS TWO OSCILLATIONS in 4 s. (iii) Frequency of oscillation is `(n) = 1//T = (1)/(2s) = 0.5 Hz.`

Discussion

4.	The vacuum kept in between the walls of a thermos flask reduces the heat transfer by :
Answer» CONDUCTION only CONVECTION only radiation only conduction and convection. ANSWER :D

Discussion

5.	As the amplitude of a vibrating body increases, the loudness of the sound produced _____
Answer» increases decreases remains same None of these Solution :The loudness of sound depends UPON the amplitude of the vibrating BODY, i.e., the more the amplitude, the more is the loudness.

Discussion

6.	A bus driver is observing the image of a car in his rear view (side) mirror. How does the size of the image change when the car approaches the bus?
Answer» SOLUTION :The mirror used in vehicles as rear view mirror is convex. So, when the object is at a large distance from the mirror, image will be at the FOCUS, i.e., a diminsihed image is OBTAINED. When the object approaches nearer and nearer, the size of image increases. So, size of the image of car in the mirror GRADUALLY increases.

Discussion

7.	Which among the followig is the unit of heat?
Answer» CALORIE Kelvin Degree centrigrade All the above Solution :Calorie is a UNIT of HEAT.

Discussion

8.	An electric bell uses an electromagnet.
Answer» ANSWER :TRUE

Discussion

9.	A frequency of 1 Hz means _________ oscillations per second.
Answer» Solution :The number of OSCILLATIONS COMPLETED in one second is called frequency. Therefore, 1 HZ frequency means one oscillation per second.

Discussion

10.	Mass of a body cannot be zero.
Answer» SOLUTION :MASS of a BODY can't be ZERO

Discussion

11.	Which of the following statements is//are incorrect?
Answer» (a) The weight OS a body can be zero. (b) The weight of a body can be GREATER than zero. (c ) The MASS of a body can be zero. (d) Both (a) and (c ). SOLUTION :Mass of a body can never be zero and the weight can be zero if th acceleration due to gravity is zero.

Discussion

12.	The primary colours are
Answer» RED, BLUE and YELLOW Magenta, Yellow and Cyan Red, Blue and Cyan Blue, GREEN and Red Answer :D

Discussion

13.	A positively charged body is brought in contact with the cap of gold leaf electroscope. Whose strips are netural , then
Answer» postively charge flows from the body to the strips and both the strips ACQUIRE POSITIVE charge. DUE to like CHARGED on strips , they arrract each other. if a positively charged body is removed the gap between the strips decreases. Both (a) and (c ). Solution :When apositively charged body is brought in con-tact with the cap ofgold leaf electroscope, the charge flows from the body to thestrips through the con-ducting rod (brass rod), and hence both the strips acquire same positive charge. Due to the presence of the like CHARGES on strips, they will repel each other. When we remove the body from contact, the strips wil remain apart.

Discussion

14.	A man going up has potential energy and kinetic energy both.
Answer» ANSWER :T

Discussion

15.	When a bulb lights up on passing current, the change of energy is
Answer» from electrical ENERGY to HEAT energy from electrical energy to LIGHT energy from electrical energy to heat and light energy from electrical energy to MECHANICAL energy. Answer :C

Discussion

16.	Angle of incidence = ..........
Answer» SOLUTION : ANGLE of REFLECTION

Discussion

17.	If the length, breadth and height of a cuboid are all increased to 'n'times their original values of 'n'.
Answer» SOLUTION :Volume of the CUBOID = `length xx BREADTH xx HEIGHT` Volume of the new cuboid = `(n xx length) xx (n xx breadth) xx (n xx height)` = `n^(3) ( length xxbreadth xx height)` Density = `mass/volume` `8/1=n^(3)/1,n^(3)=8, n=2`

Discussion

18.	Match the entries given in column A with the appropriate ones in colum B.
Answer» ANSWER :A:d,B:E,C:a,b,D:h,E:c,F:g,G:b,H:I,I:f

Discussion

19.	Match the entries given in column A with the appropriate ones in colum B.
Answer» ANSWER :A:E,B:a,C:b,D:F,E:c,F:d

Discussion

20.	Match the entries given in column A with the appropriate ones in colum B.
Answer» ANSWER :A:E,B:d,C:F,D:a,E:c,F:b

Discussion

21.	Which of the following electrical appliances works on the principle of the magnetic effect of electric current ?
Answer» ELECTRIC heater electric motor electric bell Both (B) and (C ) ANSWER :D

Discussion

22.	A farmer plough his field ,to _________
Answer» To prevent the SURFACE from becoming hard increasethe evaporation of water from the surface of FIELD make the land dry None of the above Answer :A

Discussion

23.	A car travels a certain distance with 42 km h^(-1) for 20 minutes and the remaining distance at 60 km h^(-1) for 30 minutes. What is its average speed of the whole journey ?
Answer»

Discussion

24.	Glow worm is
Answer» ANSWER :COLD or NATURAL

Discussion

25.	Convert 920 kg//m^(3) to g//cm^(3)
Answer» SOLUTION :`0.92 g//cm^(3)`

Discussion

26.	Which ofthe following devices does not work on the principle of magnetic effects of electric current?
Answer» Electromagnet Electric motor Electric generator Telegraph Answer :C

Discussion

27.	An electromagnet is used in :
Answer» ELECTRIC oven ammeter electric BELL radio set Solution :electric bell

Discussion

28.	Sound needs a ___________ to travel.
Answer» SOLUTION :SOUNDS REQUIRE a MEDIUM to TRAVEL.

Discussion

29.	The maximum displacement of a bob from its mean position is called its amplitude.
Answer» SOLUTION :The maximum displacement of a BOB from its mean position is CALLED AMPLITUDE.

Discussion

30.	If a ray of light incident on a plane mirror is such that it makes an angle of 30^@ with the mirror, then the angle made by the reflected ray with the mirror is
Answer» `35^(@)` `60^(@)` `90^(@)` `30^(@)` ANSWER :D

Discussion

31.	Choose the correct alternateice (s) among the following statements
Answer» Seed drill is USED to sow seeds Four or five ploughs are attached TOTHE palank of the sed drillto sow the seeds deeper SPEED drill is ALSO used to put mabyre bear the ROOTS of the small plants All the above Answer :D

Discussion

32.	Fill in the blanks The capacity to do work is called_____.
Answer» ANSWER :ENERGY

Discussion

33.	Komali found tha of most of the agricultural tools her father uses are made up of wood. Explain why it is so.
Answer» SOLUTION : Agriculture toosl are always is contact with the mositure, manure, etc. so, the chance of getting rotated is more when compared to workshow tools. The SIZE of the angriculture tools is more than the size of workshop tools. But theb WEIGHT of wood is less compared to the weight of METAL. THUS, most of the parts are made up of wood.

Discussion

34.	Why are concave reflectors used in big auditoria ?
Answer» Solution :Concave REFLECTORS are used in big auditoria to distribute the sound evenly in all DIRECTIONS. When the speaker is PLACED at the focus of the concave reflector, then the reflected sound waves travel PARALLEL, in all directions and can be DISTRIBUTED evenly.

Discussion

35.	If an object is placed unsymmetrically between two plane mirrors, inclined at the angle of 60^(@), then the total number of images formed is
Answer» ANSWER :11

Discussion

36.	Which of the following is a false statement about Leclanche cell ?
Answer» Electrolyte is a liquid. Zinc rod and CARBON rod ACTS as NEGATIVE and POSITIVE electrodes. It can be easily portable form place from place to place. Dry cell is a modified form of Leclanche cell. Answer :C

Discussion

37.	What make electrical energy so useful for mankind ?
Answer» SOLUTION :If there is a form of energy without which present DAYS HUMAN life is verydifficult to imagine, thenit is electrical energy. We DEPEND onelectrial energy is electrical energy. We dependon electrical energy for everything. The usefulness of electrical energyfor everything. the usefulness of electrical energy COMES because we have devices that convert elec-trical energy into any other form.Here isa list of devices that convert electrical energy into different other forms.

Discussion

38.	1 m^(3)=1000000cm^(3)
Answer» SOLUTION :1 ML=`1CM^(3)`

Discussion

39.	A negatively charged body is connected to the ground, then choose the correct statement. (A) It becomes positively charged. (B) Electrons flow from the body to the ground.
Answer» Only A is true Only B is true Both A and B are true Both A and B are false Answer :A

Discussion

40.	{:("ColumnA","ColumnB"),(A."Curbulinear motion",a."motion that repeats itself irregular intervals of time"),(B. "Rectilnear motion",b."Wings of a ceiling fan"),(C."Rotatory motion",c." A stone dropped from a towar"),(D."Body moving with uniform velocity",d."A stone dropped from a towar"),(E."Length of a pendulum",e."point of supendsion to the mid-point of the bob"),(F." Time period of a simple pendulum",f."Square root of the length of the pendulum"),(G."Non-periodic motion",g. "Zero acceleration"):}
Answer» ANSWER :A::B::C::D

Discussion

41.	In the head lights of a car, what kind of mirror are used? What is the use of mirror in the car head lights? Explain.
Answer» Solution :The mirrors used in car head lights are concave mirrors. They reflect the light from the bulb which is placed at the FOCUS. These light RAYS TRAVEL prarllel and travel longer DISTANCES.

Discussion

42.	Ram took an empty density bottle and a weighing machine. He measures the density bottle and a weighing machine. He measures the empty bottle and found it to be 40 .g. He then completely filled it with water and weighed it to be 100 g. With this data can he calculate the capacity of the density bottle? If so, what is its capacity
Answer» Solution :The mass of the WATER = 100-40 = 60 g DENSITY of water = `1 " g " cm^(-3)`Density = `"mass"/"volume" rArrVolume = "mass"/"density"`=`(60g)/ 1 " g" cm(-3)`

Discussion

43.	If a bus travels a distance of 30 km in 45 minutes. What will be its speed in: km//"hr "
Answer» SOLUTION :45MINUTES= `45//60 `HOURS = 0.75 hours SPEED in `km//h = 30//0.75= 40km//h`

Discussion

44.	The unit of heat is/are
Answer» CALORIE Kelvin Degree centrigrade All the above Solution :Calorie is a UNIT of HEAT.

Discussion

45.	The angle of incidence on a plane mirror is 30^@ . The angle between the incident ray and the reflected ray is
Answer» `30^@` `15^@` `60^@` `90^@` ANSWER :C

Discussion

46.	One surface of mirror is made opaque by ..........it followed by a thin coating of paint of lead oxide.
Answer» SOLUTION :SILVERING

Discussion

47.	A car covers a distance of 160 km between two cities in 4 h. What is the average speed of the car?
Answer» SOLUTION :`40 KM H^(-1)`

Discussion

48.	Convert 122^@F to degree Celsius and kelvin.
Answer» SOLUTION :`50^@ C` ,323 K

Discussion

49.	Unit of electromotive force is
Answer» volt second metre `MS^(-1)` ANSWER :A

Discussion

50.	Still air is an ........ of heat.
Answer» SOLUTION :INSULATOR

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

Explain the anomalous expansions of water with hope's apparatus.

The mass of a density bottle when it is filled with a liquid of density 3000 kg m^(-3)is 400 g and the mass of the bottle when it is filed with water is 200 g.The mass of the empty density bottlewhen it is filled with water is 200 g.The mass of the empty density bottle is "_____" g.

The vacuum kept in between the walls of a thermos flask reduces the heat transfer by :

As the amplitude of a vibrating body increases, the loudness of the sound produced _____

A bus driver is observing the image of a car in his rear view (side) mirror. How does the size of the image change when the car approaches the bus?

Which among the followig is the unit of heat?

An electric bell uses an electromagnet.

A frequency of 1 Hz means _________ oscillations per second.

Mass of a body cannot be zero.

Which of the following statements is//are incorrect?

The primary colours are

A positively charged body is brought in contact with the cap of gold leaf electroscope. Whose strips are netural , then

A man going up has potential energy and kinetic energy both.

When a bulb lights up on passing current, the change of energy is

Angle of incidence = ..........

If the length, breadth and height of a cuboid are all increased to 'n'times their original values of 'n'.

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

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

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

Which of the following electrical appliances works on the principle of the magnetic effect of electric current ?

A farmer plough his field ,to _________

A car travels a certain distance with 42 km h^(-1) for 20 minutes and the remaining distance at 60 km h^(-1) for 30 minutes. What is its average speed of the whole journey ?

Glow worm is

Convert 920 kg//m^(3) to g//cm^(3)

Which ofthe following devices does not work on the principle of magnetic effects of electric current?

An electromagnet is used in :

Sound needs a ___________ to travel.

The maximum displacement of a bob from its mean position is called its amplitude.

If a ray of light incident on a plane mirror is such that it makes an angle of 30^@ with the mirror, then the angle made by the reflected ray with the mirror is

Choose the correct alternateice (s) among the following statements

Fill in the blanks The capacity to do work is called_____.

Komali found tha of most of the agricultural tools her father uses are made up of wood. Explain why it is so.

Why are concave reflectors used in big auditoria ?

If an object is placed unsymmetrically between two plane mirrors, inclined at the angle of 60^(@), then the total number of images formed is

Which of the following is a false statement about Leclanche cell ?

What make electrical energy so useful for mankind ?

1 m^(3)=1000000cm^(3)

A negatively charged body is connected to the ground, then choose the correct statement. (A) It becomes positively charged. (B) Electrons flow from the body to the ground.

In the head lights of a car, what kind of mirror are used? What is the use of mirror in the car head lights? Explain.

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

The unit of heat is/are

The angle of incidence on a plane mirror is 30^@ . The angle between the incident ray and the reflected ray is

One surface of mirror is made opaque by ..........it followed by a thin coating of paint of lead oxide.

A car covers a distance of 160 km between two cities in 4 h. What is the average speed of the car?

Convert 122^@F to degree Celsius and kelvin.

Unit of electromotive force is

Still air is an ........ of heat.