885 + Interview Questions in Physics in Class 8 Page 1 InterviewSolution

1.	What are conductors ?
Answer» Answer :CONDUCTORS are materials which allow electric current to pass through them.For EXAMPLE ALUMINIUM, copper, salt solution, etc.

Discussion

2.	There are two identical bar magnets attached together as shown in the figure and suspended with the help of a thread. On being disturbed slightly, in which direction would the magnets point ?Explain your answer.
Answer» Solution :(i) what factors affect the orientation of a BAR magnet ? (II) find out the direction of magnetic field DUE to each magnet. What will the resultant magnetic field be ? Using the direction of resultant magnetic field, find the direction ALONG which the magnet points.

Discussion

3.	Fill in the blanks : Sound is produced by ________.
Answer» ANSWER :A::B

Discussion

4.	When a charged body is brought near another charged body, it will________.
Answer» ATTRACT each other REPEL each other be in a STATE of rest fall down Answer :B

Discussion

5.	_______ help scientists investigating the nature of the material from whichthe Solar System was formed..
Answer» Meteorites Comets Meteors Asteroids Answer :A

Discussion

6.	Fill in the blanks : The most comfortable distance at which one can read with a normal eye is about________ cm.
Answer» ANSWER :25

Discussion

7.	Meet an eye specialist. Get your eye sight checked and discuss how to take care of your eyes.
Answer» ANSWER :SUGGESTION : STUDENTS should do themselves.

Discussion

8.	Take a hollow coconut shell and make a musical instrument ektara. You can also make it with the help of an earthen pot. Play this instrument and identify its vibrating part.
Answer» ANSWER :The VIBRATING part of an EKTARA is the STRETCHED STRING.

Discussion

9.	Can a galvanometer as such be used for measuring the current? Explain.
Answer» Solution :How is the STRENGTH of the electric CURRENT RELATED to the deflecing angle of a GALVANOSCOPE? Is it POSSIBLE to calibrate a galvanoscope to measure current?

Discussion

10.	Fill in the blanks : If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the ___ terminal of the battery.
Answer» ANSWER :NEGATIVE

Discussion

11.	How is sound important in our life?
Answer» Answer :SOUND PLAYS a very IMPORTANT role in our LIFE as it helps US in communicating with each other.

Discussion

12.	Name the device used for measuring the force acting on ad object.
Answer» Answer :Spring balance is USED for MEASURING the FORCE acting on an object.

Discussion

13.	When a metallic sphere is released from the surface of water filled in a container of uniform area of cross section it is found to reach the bottom of the container in 2 s.If the density of the material of the sphere is 4.9 g cm^(-3), calculate the pressure exerted by the liquid at the bottom of the container. Assume that only gravitational force and up-thrust act on the body.
Answer» Solution :`(i) V_(0)XX d_(0) xx a= V_(10)xx d_(1)xxg -V_(0)xx d_(1)xx G` `A=(g(d_(0)-d_(1)))/(d_(0))` `S=ut+(1)/(2) at^(2)` P=hdg (ii) 15,2880 Pa

Discussion

14.	A current passes from south to north, through a conductor placed in a horizontal position. If a magnetic needle is placed horizontally below the conductor then it woud deflect towards
Answer» west east south north Answer :A

Discussion

15.	4500 J of energy is used to raise an object with a mass of 50 kg to a height h. Calculate h.
Answer» ANSWER :9 m

Discussion

16.	What are seismic waves?
Answer» Answer :The WAVES PRODUCED on the surface of the earth due to tremors are CALLED sesmic waves.

Discussion

17.	What is the measurement of static friction?
Answer» Answer :The FORCE REQUIRED to KEEP an object from REST is the measurement of STATIC friction.

Discussion

18.	The mechanical advantage of tongs is
Answer» ALWAYS equal to ONE always LESS than one always greater than one sometimes less than one and sometimes greater than one. Answer :B

Discussion

19.	The principle used in swimming is Newton's third law of motion.
Answer» ANSWER :TRUE

Discussion

20.	What are charged objects?
Answer» ANSWER :those objects which acquire electrical charge when they are rubbed with ANOTHER object are CALLED charged objects.

Discussion

21.	What do you observe when you push an object against the surface of another object or floor?
Answer» Answer :When we push an object against the surface of another object or FLOOR it is OBSERVED that the force of FRICTION is always opposite to the force APPLIED.

Discussion

22.	What does the distance moved by an object in unit time indicate?
Answer» ANSWER :The DISTANCE moved by an OBJECT in UNIT time INDICATES its speed.

Discussion

23.	You can recognise many familiar sounds without seeing the objects producing them. How is it possible?
Answer» Answer :We can recognise MANY familiar sounds of OBJECTS WITHOUT seeing them because different objects produce different sounds.

Discussion

24.	A straight conductor carrying current produces a magnetic field around it. Does it possess a north or a south pole similar to a bar magnet ? what shape should be given to the conductor so as to have magnetic poles ?
Answer» Solution :Recall the definition of magnetic poles. In a BAR MAGNET, its strength is concentrated at the ends. COMPARE the magentic lines of force due to a bar magnet and a current carrying conductor. How does the shape of magnetic lines of force change when a current carrying conductor is bent to FORM a circular COIL ?

Discussion

25.	The relative density of pure gold is 19.3. When an ornament made of gold is immersed completely in water, the volume of the water displaced is 5 ml. If the mass of the ornament in air is 100 g, determine whether the ornament is made of pure gold.
Answer» Solution :(i) DENSITY `=(m)/(v)` density `=("MASS")/("VOLUME of liquid displaced")` If the ornament is made of pure GOLD, the density of the ornament MUST be equal to the density of gold. (ii) `20 g cm^(-3)`

Discussion

26.	Choose the correct option (Multiple choice questions) : The impression of an image persints on the retina for about________ of a second.
Answer» `1/18`TH `1/25`th `!/16`th `1/24`th Answer :C

Discussion

27.	A disc siren with certain number of holes rotates uniformly 270 times in one and half minute. The frequency of the note emitted is 48 Hz. If the velocity of sound in air is 336 m s^(-1), find its wavelength and number of holes on the disc.
Answer» Solution :(i) `lamda = (V)/(n)`, No. of HOLES `= ("frequency")/("No. of RATATION in ONE sec")` (II) 16

Discussion

28.	The bluishwhite streak of light seen during lightning is due to
Answer» a change of colour of the clouds, ascharge PASSES between the clouds. burning of clouds producing an intense white LIGHT. air becoming white hot as charge passes between the clouds. None of the above Solution :The bluish white streakof light SEEN during LIGHTING is due to air becoming white hot as charge passes between the clouds.

Discussion

29.	Which will occupy more space- 720 g of mahogany wood (of density 0.720 "g/cm"^3) or 2710 g of marble (of density 2.71 "g/cm"^3) ?
Answer» ANSWER :Both are same as VOLUME is the same

Discussion

30.	A rectangular tank is completely filled with water. But due to leakage, water continuously flows out of it and finally, the tank is empty. Discuss the variation in the position of the centre of gravity as the water leaks out.
Answer» SOLUTION :Initially when the tank is COMPLETELY filled with WATER, the CG is at the geometric centre of the trank. But as the water leaks out, the CG SHIFTS downward.When water leaks out completely such that the tank is now empty, the CG agin reaches the geometric centre.

Discussion

31.	What are longitudinal waves ? Give examples. How do such waves propagate ?
Answer» in a metal but not in a gas in a gas but not in a metal neither in a metal nor in a gas both in a metal and in a gas Solution :Longitudinal waves can propagate both in SOLIDS and gases and also in LIQUID

Discussion

32.	When we speak does any part of our body vibrate?
Answer» ANSWER :YES, when we SPEAK our VOCAL chords vibrate.

Discussion

33.	Fill in the blanks : The passage of an electric current through a solution causes ___ effects.
Answer» ANSWER :CHEMICAL

Discussion

34.	Choose the càrrect oplion in Questions. Angle of incidence is equal to the angle of reflection.
Answer» Always Sometimes Under SPECIAL conditions Never Answer :A

Discussion

35.	Find the force between two parallel conductors carrying currents (i) in the same direction (ii) in opposite directions and hence define one ampere.
Answer» Solution :IDENTIFY the direction of magnetic field produced by each WIRE when current flows through them. Identify whether the force is attractive or repulsive when the magnetic fields AREIN the same direction and opposite direction ?

Discussion

36.	Compression and rarefactions are formed in______
Answer» STATIONARY TRANSVERSE wave sound wave light wave water wave Answer :B

Discussion

37.	Can we have a single north pole, or a single south pole?
Answer» ANSWER :F

Discussion

38.	When we touch a charged object, it gets _______
Answer» NEGATIVELY charged positively charged discharged NONE of these Answer :C

Discussion

39.	A cylindrical object flats in water such that (3//4) th of its volume is immersed in water. Its density is _____ kg m^(-3).
Answer» Solution :`(d_(0))/(d_(w))=(3)/(4)` `d_(w)=(3)/(4)xx1000` `750 kg m^(-3)`

Discussion

40.	How can current be checked?
Answer» ANSWER :We can CHECK CURRENT with the HELP of a TESTER.

Discussion

41.	In a Bramah press a small force is used to spend a much larger force. This is accomplished by
Answer» increasing the AREA of cross SECTION of the PUMP piston. decreasing the area of cross section of the press piston. increasing the area of cross section of the press piston. increasing the long (weight) on the press piston. Solution :By increasing the area of cross section of the press piston, we can MAKE a Bramah press EXERT a much larger force.

Discussion

42.	Fill in the blanks : Liquids exert _____ pressure at the same depth.
Answer» ANSWER :EQUAL

Discussion

43.	What could cause a disturbance inside the earth?
Answer» ANSWER :the disturbances INSIDE the EARTH's crust are caused by the collision of different tectonic plates.

Discussion

44.	Coal is a renewable source of energy.
Answer» ANSWER :F

Discussion

45.	Fill in the blanks : Sliding friction is ______ thanrolling friction.
Answer» ANSWER :GREATER

Discussion

46.	The wavelength of a sound wave travelling in a solid becomes one third when it propagates through air. If the frequency of the wave remains constant, then find the decreases in the velocity of the wave
Answer» Solution :(i) `(V_(1))/(V_(2)) = (lamda_(1))/(lamda_(2)), V_(1) - V_(2)` (II) `2//3`

Discussion

47.	Which of these is not a determinant of friction?
Answer» SMOOTHNESS of the surface How HARD the TWO SURFACES are pressed Shape of the object Height of the object Answer :D

Discussion

48.	How can less expensive material get the appearance of silver and gold?
Answer» Answer :By electroplating the LESS expensive material GET the APPEARANCE of silver and GOLD.

Discussion

49.	State whether the following statements are true or false : The to and fro or back and forth motion of an object is called vibration.
Answer» ANSWER :A

Discussion

50.	Find the ratio of frequency of two pendulum whose lengths are in the ratio 1 : 4
Answer» SOLUTION :`(f_(1))/(f_(2)) = SQRT((l_(2))/(l_(1))) = sqrt((1)/(4)) = 1:2`

Discussion

Explore topic-wise InterviewSolutions in .

What are conductors ?

There are two identical bar magnets attached together as shown in the figure and suspended with the help of a thread. On being disturbed slightly, in which direction would the magnets point ?Explain your answer.

Fill in the blanks : Sound is produced by ________.

When a charged body is brought near another charged body, it will________.

_______ help scientists investigating the nature of the material from whichthe Solar System was formed..

Fill in the blanks : The most comfortable distance at which one can read with a normal eye is about________ cm.

Meet an eye specialist. Get your eye sight checked and discuss how to take care of your eyes.

Take a hollow coconut shell and make a musical instrument ektara. You can also make it with the help of an earthen pot. Play this instrument and identify its vibrating part.

Can a galvanometer as such be used for measuring the current? Explain.

Fill in the blanks : If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the ___ terminal of the battery.

How is sound important in our life?

Name the device used for measuring the force acting on ad object.

A current passes from south to north, through a conductor placed in a horizontal position. If a magnetic needle is placed horizontally below the conductor then it woud deflect towards

4500 J of energy is used to raise an object with a mass of 50 kg to a height h. Calculate h.

What are seismic waves?

What is the measurement of static friction?

The mechanical advantage of tongs is

The principle used in swimming is Newton's third law of motion.

What are charged objects?

What do you observe when you push an object against the surface of another object or floor?

What does the distance moved by an object in unit time indicate?

You can recognise many familiar sounds without seeing the objects producing them. How is it possible?

A straight conductor carrying current produces a magnetic field around it. Does it possess a north or a south pole similar to a bar magnet ? what shape should be given to the conductor so as to have magnetic poles ?

The relative density of pure gold is 19.3. When an ornament made of gold is immersed completely in water, the volume of the water displaced is 5 ml. If the mass of the ornament in air is 100 g, determine whether the ornament is made of pure gold.

Choose the correct option (Multiple choice questions) : The impression of an image persints on the retina for about________ of a second.

A disc siren with certain number of holes rotates uniformly 270 times in one and half minute. The frequency of the note emitted is 48 Hz. If the velocity of sound in air is 336 m s^(-1), find its wavelength and number of holes on the disc.

The bluishwhite streak of light seen during lightning is due to

Which will occupy more space- 720 g of mahogany wood (of density 0.720 "g/cm"^3) or 2710 g of marble (of density 2.71 "g/cm"^3) ?

A rectangular tank is completely filled with water. But due to leakage, water continuously flows out of it and finally, the tank is empty. Discuss the variation in the position of the centre of gravity as the water leaks out.

What are longitudinal waves ? Give examples. How do such waves propagate ?

When we speak does any part of our body vibrate?

Fill in the blanks : The passage of an electric current through a solution causes ___ effects.

Choose the càrrect oplion in Questions. Angle of incidence is equal to the angle of reflection.

Find the force between two parallel conductors carrying currents (i) in the same direction (ii) in opposite directions and hence define one ampere.

Compression and rarefactions are formed in______

Can we have a single north pole, or a single south pole?

When we touch a charged object, it gets _______

A cylindrical object flats in water such that (3//4) th of its volume is immersed in water. Its density is _____ kg m^(-3).

How can current be checked?

In a Bramah press a small force is used to spend a much larger force. This is accomplished by

Fill in the blanks : Liquids exert _____ pressure at the same depth.

What could cause a disturbance inside the earth?

Coal is a renewable source of energy.

Fill in the blanks : Sliding friction is ______ thanrolling friction.

The wavelength of a sound wave travelling in a solid becomes one third when it propagates through air. If the frequency of the wave remains constant, then find the decreases in the velocity of the wave

Which of these is not a determinant of friction?

How can less expensive material get the appearance of silver and gold?

State whether the following statements are true or false : The to and fro or back and forth motion of an object is called vibration.

Find the ratio of frequency of two pendulum whose lengths are in the ratio 1 : 4