821 + Interview Questions in Physics in Class 7

1.	If a glass rod is positively charged, then it consists of particles with
Answer» only POSITIVE charge. only negative charge. both negative and positive CHARGES, but the num-ber of positively charged particles are more than the number of negatively charged particles. both negative and positive charged BU the num-ber of negatively charged particles are more than the number of positively charged particles. Solution :All bodies are MADE up of negatively charged and positively

Discussion

2.	The vibrations of a turning fork are ____ in nature.
Answer» oscillatory periodic Both (a) and (B) NONE of these Answer :C

Discussion

3.	Density of a liquid can be measured by using______.
Answer» SPRING balance measuring cylinder DENSITY BOTTLE physical balance Solution :The density of LIQUID can be measured by USING a density bottle.

Discussion

4.	The heat absorbed bya substance decreases with increases in temperature
Answer» SOLUTION :HEAT absorbed BYA substance increase with the increase in temperature

Discussion

5.	Waveforms of two different stringed instruments can be the same.
Answer» ANSWER :F

Discussion

6.	(a) Two charged bodies, A and B are suspended from a fixed point with the help of silk threads as shown in the figure. If A is positively charged can we identify the nature of charge on 'B' ? (b) A negatively charged conducting sphere A and a neutral sphere B are kepton insulating stands and brought cose to each other. The charge distri-bution is as shown in the figure. Is B charged ? What type of force exists between A and B ?
Answer» Solution :(a) From the figure, we know that there is a repul-sive force between A and B, A repulsive force exist between like charges. Since A is POSITIVELY charged, B must be positively charged. (b) If we observe the figure, we see that on B, positivechrage is distributed on left SIDE WHEREAS, negative charge is distributed on the RIGHT side. As they are equal in magnitudes , the net charge on B is zeor. Redistribution of charges has TAKEN place in B when it is placed near a negatively charged body A because of electric induction. There will be attractive force between A and B.

Discussion

7.	Which of the following is (are) man made source(s) of light?
Answer» INCANDESCENT lamp Fluorescent lamp. Hurricane lamp All the above. Solution :AMONG the given OPTIONS, all the given SOURCES of light are man MADE.

Discussion

8.	1 decibel = ______________ bell.
Answer» `10` `1//10` `100` `1//100` ANSWER :B

Discussion

9.	A test tube is filled with some water .A small piece of wax is fixed at the bottom of the test tube and small piece of wax is made to float on the water what happens to the wax at the top and bottom of the test tube if the test tube is heated at the top middle and bottom?
Answer» Solution :By heating the test TUBE at its top the wax present at top surface will only melt but the wax present at the bottom of the test tube in water does not melt as thereris no transfer of HEAT in the donnword DIRECTION by convection so the temperture of water at the bottom of the test tube remains constant and there is no change in the state of wax present at the bottomby heating the test tube at the middle the wax at the top surface will melt but the wax present at the bottom surface remains same because heat covection takes place in upwared direction only by heating the test tube at bottom both the wax present at top and bottom melt because heat gets transferred from bottom to top DUE to convection

Discussion

10.	Materials that do not allow electric charges to flow through then are called "______".
Answer» Solution :Materials that do not allow ELECTRIC changes to FLOW through THEMS are called insulators.

Discussion

11.	The device that can be used to detect the presenceof current in a circuit is "_____"
Answer» MAGNETIC compasss cell an inverter voltmeter Answer :A

Discussion

12.	Humans are sensitive to sound of loudness from __________ to ________.
Answer» SOLUTION :Human's are sensitive to sound of loudness from 10 DB to 180 dB.

Discussion

13.	In the process of convection, heat travels :
Answer» SIDEWAYS DOWNWARDS UPWARDS in all directions Answer :C

Discussion

14.	The order of magnitude of velocity of sound in solids, liquids and gases is _____. (V_(s) = velocity in solids, V_(t) = velocity in liquids and V_(g) = velocity in gases)
Answer» `V_(g) GT V_(L) gt V_(s)` `V_(s) gt V_(g) gt V_(l)` `V_(g) lt V_(l) lt V_(s)` `V_(s) = V_(g) = V_(l)` ANSWER :C

Discussion

15.	The heat required to raise the temperature of 1 kg of water by 1^(@)C is called one calorie
Answer» Solution :The heat required to raise the TEMPERATURE of 1kg of water by `1^(@)C` is CALLED one kilocatorie

Discussion

16.	A sound wave is travelling from a metallic rod to water. What changes will occur in the velocity and frequency of the sound ?
Answer» Solution :As the sound is produced by a vibrating source, the number of vibrations COMPLETED by that source in 1 s remains same, i.e., the frequency of sound wave remains constant even THOUGH it travels from one medium to another. Sound travels with different speeds in different MEDIA. As it is ENTERING from solid (metalic rod) to water (liquid), its VELOCITY (speed) decreases.

Discussion

17.	Density of water is_____than the density of cooking oil.
Answer» ANSWER :GREATER

Discussion

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

Discussion

19.	The purpose of armature in an electric bell is :
Answer» to MAKE and BREAK the circuit to produce SOUND to produce magnetic field to PROVIDE SPRING action. Solution :to make and break the circuit

Discussion

20.	The odometer of a motorcycle shows a reading of 10,237 km at 8.30a.m.At 9.00 a.m., it shows a reading 10,267 km, what is the speed of the motorcyle in Kmh-1?
Answer»

Discussion

21.	Answer the following question Why white clothes are comfortable in summer?
Answer»

Discussion

22.	Fill in the blanks A black body absorbs _________ heat energy than a white body
Answer» ANSWER :CONDUCTION

Discussion

23.	A simple pendulum of length of and time period 'T' on earth is taken onto the surface of moon. How should the length of the simple pendulum be changed on the moon suchthat the time period it constant . ( Takeg_(r)= 6 g_(m))
Answer»

Discussion

24.	Sound travels much _____ than light in a given medium.
Answer»

Discussion

25.	A thermometer worked on the principle of
Answer» linear expansion of solid CUBICAL expansion of solid uniform expansion of volume of LIQUID or gas with temperature both a and c Solution :Thermometer worked on the PRINICIPLE of cubical expansion of liquid or gas And this expansions should be uniform thourghout the MATERIAL

Discussion

26.	For each of the question four choice have beenporvided select the correct alternative Choose the correcty statement
Answer» specific heat capacity of a body in all its STATES is constant specific heat capacity of a body is differentin different states specific heat capacity is a characteristic property of a material and it is different for different material both BAND c Solution :Specific heat capacity of a body is the amount of het energy requird to raise the temperture of UNITS mass of substance through`1^(@)C` .It is the characteristic proprerty of a body and it remains constant in a given STTE but changes form state to state for a given substance

Discussion

27.	Rahul, by using a hace salw blade,was cutting metal pipes to supply water to house. What will happen if he starts moving the hack saw blade very fast over the metal, due to lack of time
Answer» SOLUTION : If we move the hack saw blade very fast over the WORK piece, due to friction, the blade GETS heated up and it willdemate the shapnees of teethc, So, the efficiency of the blade will be REDUCED, and when we move it very fast over the cutting METAL, there is a chance of breaking the hack saw balde.

Discussion

28.	What will happen to the strips of a positively charged electroscope when a positively charged and another negtively charged bodies with equal magnitude of charge are brought simultaneously in contact with the cap of a positively charged electroscope?
Answer» move apart. come closer. remains uneffected Cannot be DETERMINED Solution :When prositively charged and netgatively charged bodies are brought in contact with the brass cap of the gold leaf electroscope-both the CHARGE neutral-ize each other and the net charge will be ZERO on the cap of electroscope,and hence the charge on strips flows to the bodies brought in CONTACTWITH the cap and due to this the grap between strips decreases.

Discussion

29.	A bat entering into a well finds it difficult to come out of it. Explain the reason.
Answer» SOLUTION :When the bat is inside the well, it produces the ULTRASONIC sound to come out of it. The sound PRODUCED by it gets reflected from all the sides, and HENCE, it becomes difficult for the bat to find a path to come out of the well.

Discussion

30.	The length of the straight line joining the centre of curvature and any point on the surface of a spherical mirror is the ______ of the mirror.
Answer» FOCAL length PRINCIPAL axis radius of corvature optic axis Solution :The length of the straight line JOINING the centre of curvature and any point on the surface of a SPHERICAL mirror is the radius of curvature of the mirror (R).

Discussion

31.	The image formed by a plane mirror is
Answer» VIRTUAL and INVERTED virtual and of same size REAL and inverted real and of same size Answer :B

Discussion

32.	Which of the following is (are) natural source(s) of light?
Answer» PLANETS GLOW worm Stars Both (B) and (C) ANSWER :D

Discussion

33.	Heat flows from a body at a high temperature to a body at a low temperature when they are kept in contact
Answer» ANSWER :T

Discussion

34.	Mass of a given substance does not change with change in position or location.
Answer» SOLUTION :The mass of a GIVEN substance does not CHANGE with change in POSITION or LOCATION.

Discussion

35.	Land and sea breezes are convection currents of cold and warm air.
Answer» ANSWER :T

Discussion

36.	The modern unit of intensity of light is ______.
Answer» lumen candle power lux All the above.

Discussion

37.	Give two examples for each of the motion along a stright line, circular motion and periodic motion.
Answer»

Discussion

38.	The use of metal balde in a plough is __________
Answer» to PENETRATE DEEP into the SOIL easily to give strength to the L-shaped log. to avoid breaking of wooden log when it strikes a STONE All the above Answer :A

Discussion

39.	The line joining the centre of curvature and pole of the mirror is called. ______.
Answer» the principal axis y-axis the CENTRE axis None of these Solution :The line joining the CENTER of curvature and pole of the MIRROR is called principal axis of the mirror.

Discussion

40.	_________ is used to remove weeds in a field
Answer» Solution :Hoe is used REMOVE WEEDS in a FIELD

Discussion

41.	Raghavan found a metallic rod AB and a glass rod CD both positively charged and placed on an insulat-ing table. He wanted to know what would happen to the charges on AB and CD if he touched both the rod at A and C ? Discuss.
Answer» Solution :Metals are conductors and glass is an insulator. If a person TOUCHES a charged body, the body LOSES to charge to ground and this is known as 'earthing'. In case of a metallic rod, charges are free to move through the body, and even if the person touches the body at 'A', the body loses its WHOLE charge to the earth. Where as in case of glass rod,only the charge that is in CONTACT with the person gets earthed and the remaining charge on 'CD' will REMAIN as it is.

Discussion

42.	The line joining the pole and the centre of curvature of a mirror is called the
Answer» the PRINCIPAL axis y-axis the CENTRE axis None of these Answer :A

Discussion

43.	Define live and neutral wires.
Answer» Solution :Electrical ENERGY is SUPPLIED to houses through two wires, LIVE and neutral wires. If any appliance is to the electrical energy. One end of the appliance is to be connected to a live wire and other end of the appli-ance is to be connected to a neutral wire. Electric current passes from the live wire to neutral wire through the appliance. In this PROCESS, electrical energy is converted to other FORMS of energy.

Discussion

44.	Ria covered a distance of 600 m in two minutes whereas Lia covered the same distance in three minutes. Who is faster?
Answer» SOLUTION :Ria.s SPEED `600//2 = 300 m//"MIN"` Lia.s speed `600//3 = 200 m//"min"`

Discussion

45.	We can tighten or loosern screw by using _________
Answer» Solution :We can tighten or LOOSEN SCREWS by USING a SCREW driver

Discussion

46.	A physics scholar took two spring balances 'S_(1)' and (s_(2) that are calibrated on the surface of the Moon and the Earth, respectively. He then weighed a body using both S_(1) and S_(2) at a given place on the surface of the earth. He determind the ratio of the readings. What is the ratio?S
Answer» SOLUTION :Here, the READINGS on the spring balances remain the same as the weight of he same object is measured. So, each spring balance SHOWS same READING. Hence, the ratio is `1 : 1`.

Discussion

47.	Match the entries given in Column A with the appropriate ones in Column B. {:("Column A","Column B"),(A."Intensity of light",(" ")a."Plane mirror"),(B."Rainbow",(" ")b."Shadow"),(C."Looking glass",(" ")c."Hot source"),(D."Eclipse",(" ")d."Lumen"),(E."Filament bulb",(" ")e."Dispersion"):}
Answer» ANSWER :A : D B : E C : A D : B E : C

Discussion

48.	We are able to see the objects around us due to ................... reflection.
Answer» SOLUTION :IRREGULAR

Discussion

49.	Calorific value of___________ fuels is high
Answer» Solution :Gaseous FUELS have HIGH calorfic VALUE COMPARED to SOLID fuels and liquid fuels

Discussion

50.	Atom is considered neutral because it contains an equal number of "________" and "______" charges.
Answer» Solution :Atom is CONSIDERED neutral because it contains an EQUAL number of positive and negative CHARGES.

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

If a glass rod is positively charged, then it consists of particles with

The vibrations of a turning fork are ____ in nature.

Density of a liquid can be measured by using______.

The heat absorbed bya substance decreases with increases in temperature

Waveforms of two different stringed instruments can be the same.

Which of the following is (are) man made source(s) of light?

1 decibel = ______________ bell.

A test tube is filled with some water .A small piece of wax is fixed at the bottom of the test tube and small piece of wax is made to float on the water what happens to the wax at the top and bottom of the test tube if the test tube is heated at the top middle and bottom?

Materials that do not allow electric charges to flow through then are called "______".

The device that can be used to detect the presenceof current in a circuit is "_____"

Humans are sensitive to sound of loudness from __________ to ________.

In the process of convection, heat travels :

The order of magnitude of velocity of sound in solids, liquids and gases is _____. (V_(s) = velocity in solids, V_(t) = velocity in liquids and V_(g) = velocity in gases)

The heat required to raise the temperature of 1 kg of water by 1^(@)C is called one calorie

A sound wave is travelling from a metallic rod to water. What changes will occur in the velocity and frequency of the sound ?

Density of water is_____than the density of cooking oil.

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

The purpose of armature in an electric bell is :

The odometer of a motorcycle shows a reading of 10,237 km at 8.30a.m.At 9.00 a.m., it shows a reading 10,267 km, what is the speed of the motorcyle in Kmh-1?

Answer the following question Why white clothes are comfortable in summer?

Fill in the blanks A black body absorbs _________ heat energy than a white body

A simple pendulum of length of and time period 'T' on earth is taken onto the surface of moon. How should the length of the simple pendulum be changed on the moon suchthat the time period it constant . ( Takeg_(r)= 6 g_(m))

Sound travels much _____ than light in a given medium.

A thermometer worked on the principle of

For each of the question four choice have beenporvided select the correct alternative Choose the correcty statement

Rahul, by using a hace salw blade,was cutting metal pipes to supply water to house. What will happen if he starts moving the hack saw blade very fast over the metal, due to lack of time

What will happen to the strips of a positively charged electroscope when a positively charged and another negtively charged bodies with equal magnitude of charge are brought simultaneously in contact with the cap of a positively charged electroscope?

A bat entering into a well finds it difficult to come out of it. Explain the reason.

The length of the straight line joining the centre of curvature and any point on the surface of a spherical mirror is the ______ of the mirror.

The image formed by a plane mirror is

Which of the following is (are) natural source(s) of light?

Heat flows from a body at a high temperature to a body at a low temperature when they are kept in contact

Mass of a given substance does not change with change in position or location.

Land and sea breezes are convection currents of cold and warm air.

The modern unit of intensity of light is ______.

Give two examples for each of the motion along a stright line, circular motion and periodic motion.

The use of metal balde in a plough is __________

The line joining the centre of curvature and pole of the mirror is called. ______.

_________ is used to remove weeds in a field

Raghavan found a metallic rod AB and a glass rod CD both positively charged and placed on an insulat-ing table. He wanted to know what would happen to the charges on AB and CD if he touched both the rod at A and C ? Discuss.

The line joining the pole and the centre of curvature of a mirror is called the

Define live and neutral wires.

Ria covered a distance of 600 m in two minutes whereas Lia covered the same distance in three minutes. Who is faster?

We can tighten or loosern screw by using _________

A physics scholar took two spring balances 'S_(1)' and (s_(2) that are calibrated on the surface of the Moon and the Earth, respectively. He then weighed a body using both S_(1) and S_(2) at a given place on the surface of the earth. He determind the ratio of the readings. What is the ratio?S

Match the entries given in Column A with the appropriate ones in Column B. {:("Column A","Column B"),(A."Intensity of light",(" ")a."Plane mirror"),(B."Rainbow",(" ")b."Shadow"),(C."Looking glass",(" ")c."Hot source"),(D."Eclipse",(" ")d."Lumen"),(E."Filament bulb",(" ")e."Dispersion"):}

We are able to see the objects around us due to ................... reflection.

Calorific value of___________ fuels is high

Atom is considered neutral because it contains an equal number of "________" and "______" charges.

Humans are sensitive to sound of loudness from __ to .

Atom is considered neutral because it contains an equal number of "__" and "" charges.