821 + Interview Questions in Physics in Class 7

1.	Convert 5^@F to the celsius scale
Answer» SOLUTION :`-15^@C`

Discussion

2.	Two beaker contain hot water of the same temperature one beaker is placed in anotehr beaker containing cold water and the other breaker in fornt ofa rotating fan .It is observed that the beaker placed infront fan cools faster .explain the reason
Answer» Solution :The beaker which is placed in front of a rotating FAN wil cool first when the beaker is ein water the cold water absorbs heat but when it is in FONT of a rotatingfan the heat tranfer is due to forced convection of air .Heat TRANSFER RATE is more in forced convection so the beaker placed in front of a rotating fan COOLS faster

Discussion

3.	The distance- time graph of a car isas shown in the figure. Is the car moving with constant speed? Find the speed of the car at the end of 2 hour and 6 hour, respectively,
Answer»

Discussion

4.	Electric heater works on the basis of "_______" the electric current.
Answer» SOLUTION :Electric heater works on the BASIS of heating EFFECT of the electric current.

Discussion

5.	The sounds of frequencies greater than 20 kHz are called ultrasonic sounds.
Answer» SOLUTION :The sounds with FREQUENCIES greater than 20 KHZ are CALLED ultrasounds.

Discussion

6.	A boy goes to a shop, which is 3 km away, buys things and comes back. What is the distance and displacement in km and m?
Answer» SOLUTION :6 KM, 6,000 m DISPLACEMENT is ZERO

Discussion

7.	Choose the correct statement : When a positively charged body is placed on the ground. (A) the electrons flow from the ground and neutral-ize the charge. (B) the electrons flow from the ground and charge it negatively.
Answer» only A is true only B is true Both A and B are true Both A and B are false Solution :When a positively CHARGED body is kept on the ground, electrons from the ground flow to the body and neutralizes the excess charge (POSITIVE) present in the body, the and hence, the body acquires no CHARGES, i.e, it BECOMES neutral body.

Discussion

8.	An empty bottle weighs 30 g. It weighs 54 g when filled with kerosene. If the volume of the bottle is 30 mL, find the density of kerosene in g//cm^(3) and in kg//m^(3)
Answer» Solution :Mass of kerosene = 54 - 30 = 24 G Volume of kerosene = `30 mL = 30 CM^(3)` Density= `24//30=0.8g//cm^(3)=800 kg//m^(3)`

Discussion

9.	Fill in the blanks The process of changing a substance from gaseous state to liquid state is called_______.
Answer» ANSWER :CONDENSATION

Discussion

10.	An electromagnet with soft iron core is a temporary magnet.
Answer» ANSWER :TRUE

Discussion

11.	Magenta, cyan and yellow are the......... colours.
Answer» SOLUTION :SECONDARY

Discussion

12.	The direction of light can be changed by ______
Answer» a PLANE mirror a PIECE of paper a STONE All the above. Answer :D

Discussion

13.	{:(,"Column A",,, "Column B"),(A., anglei = angler, (), a., 0.1 s),(B., "Persistence of hearing", ( ), b., "Infrasonic"),(C., "Dolphins", ( ), c., "Law of reflection of sound"),(D., "Carpets", ( ), d., "Echoes"),(E., 10 Hz, (), e., "Reduce noise pollution"):}
Answer» Solution :A - c `" "` When a sound wave is reflected, the angle of incident sound (i) is equal to the angle of reflected sound. B - a `" "` The persistence of hearing HUMANS is 0.1 s. C - d `" "` Dolphins use echo method to CATCH their PREY. D - e `" "` Carpets are sound ABSORBING materials and reduce noise pollution. E - b `" "` Sound with frequencyless than 20 Hz is knownas infrasonic.

Discussion

14.	What is maximum - minimum thermometer ?
Answer» Solution :The maximum and minimum temperatures of a CERTAIN PERIOD of a time in WEATHER REPORTS are measured by a thermometer called maximum–minimum thermometer.

Discussion

15.	The temperature of a body rises by 1^@C. What is the corresponding rise on the Fahrenheit scale
Answer» SOLUTION :`1.8^@F`

Discussion

16.	Two Cars A and B move on a stright road for the same time. Car A covers 80 , and car b covers 100m. Which one of the two is faster ?
Answer»

Discussion

17.	Sriharsha had adoublt as towhy the head of a screw drives is made of plastic material and not metal. Clarify his doubt.
Answer» SOLUTION : The head of the SCREW drives are MADE up ofplastic MATERIAL to avoid the electric cotacnt between the screw and the handle is provided to avoid electric shock.

Discussion

18.	Two astronauts who land on the moon cannot talk with each other. What could be the reason for this ? Suggest a method for them to talk each other.
Answer» Solution :Sound requires a medium to PROPAGATE. As there is no atmosphere (or) medium on the moon for propagation of sound, the words of one astronaut cannot be heard by another. If they have an medium for propagation of sound between them (LIKE a TOY phone), they can communicate with each other with the help of radio WAVES.

Discussion

19.	An object moving along a straight line with a constant speed is said to be in _____
Answer» Solution :An object moving ALONG a straight line with a CONSTANT SPEED is SAID to be in uniform motion.

Discussion

20.	For each of theequation four choices have been provided. select the correct alternative On heating a substance which of the following physical quantities changes?
Answer» DENSITY mass volume both and c Answer :d

Discussion

21.	Assertion (A): A rianbow is formed when white light is inicdent on raindrops. Reason (R): White light contains seven colours and it undergoes dispersion inside a raindrop.
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 correct explanation of A. A is correct and R is incorrect. Both A and R are incorrect. Solution :White light contains all the SEVEN colours of light. When white passes through light raindrops, under certain CONDITIONS, it undergoes DISPERSION and forms a rainbow. So, A and R are correct and R is the correct explanation of A.

Discussion

22.	During a thunderstorm, the thunder is heard 2.5 seconds after the flash of lightning is seen. If the speed of sound is 330 m s^(-1)find the distance at which lightning took place.
Answer» Solution :GIVEN : TIME taken by sound t = 2.5 s. SPEED of sound V = 330 `m s^(-1)` Speed of soundV=d/t Distance `d = V XX t = 330 xx 2.5 = 825 m`.

Discussion

23.	Give an example where translatroy and rotatory motion occurs simultaneously .
Answer»

Discussion

24.	The farmer controls the direction of the plough and depth of the soil ploughed, by the __________
Answer» HANDLE blade Long pole main plough Solution :The FARMER uses the handle to cannot the direction of the plough and DEPTH of the soil PLOUGHED.

Discussion

25.	Rama watched in discovery channel that ini outer space, at greater heights above the surface of the Earth where atmosphere does not exist appears completely dark. Explain what would be the reason for this?
Answer» Solution :At gerater heights above the SURFACE of the EARHT it APPEARS complete dark, as there exist no SCATTERING particles (DUST or moisture).

Discussion

26.	The velocity of sound is maximum in ______
Answer» liquids solids gases Cannot be determined Answer :B

Discussion

27.	______ mirror is used as shaving mirror.
Answer» SOLUTION :A CONCAVE MIRROR is USED as SHAVING mirror.

Discussion

28.	A block is 8 cm long, 2 cm wide, and 3 cm high and has a mass 375 g. What is its density?
Answer» Solution :MASS = 375 g Volume =` 8 cm xx 2 cm xx 3 cm = 48CM^(3)` Density = `375//48 = 7.8 g//cm^(3)`

Discussion

29.	Our body is a conductor of electricity.
Answer» ANSWER :TRUE

Discussion

30.	As the temperature of the gas decreases, its density_____.
Answer» ANSWER :INCREASES

Discussion

31.	__________ is used to cut thin sheets of metal
Answer» SOLUTION :We can use tin CUTTER to CUT THIN sheets of metal

Discussion

32.	Image of an object in a convex mirror is
Answer» ERECT VIRTUAL inverted Both (a) and (B) ANSWER :D

Discussion

33.	Read the following statements and choose the correct option. (A) Onlly a point source forms a complete umbra. (B) An extended source forms a complete umbra and penumbra.
Answer» Only A is true Only B is true Both A and B are true Both A and B are false Solution :Only a POINT source of light FORMS a complete dark patch on a screen, i.e., umbra. An extended source of light forms both umbra and penumbra.

Discussion

34.	A light ray is incident along the principal axis of a mirror after reflection ______.
Answer» retraces its path passes through CENTER of curvature makes zero angle with the normal. All the above. Solution :The light ray which is incident along the PRINCIPAL axis of a MIRROR falls NORMALLY on the mirror, and hence, it retraces its path. From the figure it is clear that is passes through the centre of curvature. As the line passing through the centre of curvature is PERPENDICULAR to the mirror, the angle made by the light ray with the normal is zero.

Discussion

35.	No medium is required for transferof heat by the process of convection
Answer» SOLUTION :A MEDIUM is required for the TRANSFER of HEAT by the PROCESS of convection

Discussion

36.	The vibratory motion of a tuning fork is ________ in nature.
Answer» SOLUTION :The motion of a tuning FORK is periodic, i.e., which repeats itself in equal INTERVALS of time.

Discussion

37.	What is an odometer and a speedometer gt
Answer»

Discussion

38.	What is a seconds pendulum ? What is its approximate length ?
Answer»

Discussion

39.	Answer the following question What are the animals and plants living in polar region?
Answer»

Discussion

40.	Heat in a liquid is transferred by :
Answer» CONDUCTION CONVECTION RADIATION conduction and radiation ANSWER :B

Discussion

41.	A man standing in front of a plane mirror finds his image to be at a distance of 6 metre from himself. The distance of man from the mirror is :
Answer» 6m 3m 2m 12m Answer :B

Discussion

42.	Arrange the following steps about the working of a periscope in sequential order. (A) The reflected light from the first mirror incidents on the second mirror with and angle of 45^(@) to the normal and rotates by 90^(@) (B) A reflecting periscope consistsof a tube bentwice at right angles. Two plane mirrors are provided at the bends with an angle of 45^(@) with the frame of the tube. (C) The reflected light from the second mirror comes out of the tube and enters the eye and causes the sensation of veision. (D) The light rays from the object enter the periscope from the upper tube and are incident on the first mirror with an angle of incident as 45^(@).
Answer» BDAC BCAD BADC ABCD Solution :A REFLECTING periscope consists of a tube bent TWICE at right angles. Two plane mirrors are provided at the bends with an angle of `45^(@)` with the frame of the tube. If the light rays coming from the object ENTERS te periscope from the upper tube and are incidnet on the first mirror with an angle of incidence `45^(@)`. The reflected light from the first mirror with an angle of incidence `45^(@)` with the normal, then the reflected light rotates by `90^(@)`. The reflected light from the second mirror comes out of the tube and enters the eye and causes the sensation of VISION.

Discussion

43.	{:(,"Column A",,, "Column B"),(A., "Piano", (), a., "Percussion instrument"),(B., "Mridangram", ( ), b., "Stringed instrument"),(C., "Shehnai", ( ), c., "Reflection of sound"),(D., "Sonar", ( ), d., "Ghana vadya"),(E., "Jal tarang", (), e., "Wind instrument"):}
Answer» Solution :A - b `" "` PIANO is an EXAMPLE of stringed instrument. B -a `" "` MRIDANGAM is a percussion instrument. C - e `" "` Shehnai is a WIND instrument. D - c `" "` Sonar works on the principle of reflection of sound. E - d `" "` Jal tarang is a Ghana vadya.

Discussion

44.	Electricity does not flow through:
Answer» HUMAN body animal's body RUBBER silver Solution :rubber

Discussion

45.	The sound of loudness of sound in the range of 15 dB - 16 dB is
Answer» not audible just audible moderate PAINFUL to the EAR. Solution :Sound above 150 dB, or 15 B is painful to human ear.

Discussion

46.	Which of the following is a good conductor of electricity.
Answer» impure water Glass ebonite Wood Solution :Among the GIVEN OPTIONS impure water is the BEST CONDUCTOR of electricity.

Discussion

47.	For each of theequation four choices have been provided. select the correct alternative Normal temperature of the human body is _________.
Answer» 87K 273 K `37^(@)C` `82^(@)F` ANSWER :c

Discussion

48.	One form of energy cannot be converted into another form. True/False.
Answer» ANSWER :F

Discussion

49.	A Kelvin scale reads temperature to be 318 K. What is the temperature in ""^@C and in ""^@F?
Answer» SOLUTION :`45^@ C , 113^@ F`

Discussion

50.	The loudness of sound ________ with increase in the energy spent to vibrate a body.
Answer» Solution :The loudness of sound INCREASES with increases in the energy SPENT to VIBRATE a BODY.

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

Convert 5^@F to the celsius scale

Two beaker contain hot water of the same temperature one beaker is placed in anotehr beaker containing cold water and the other breaker in fornt ofa rotating fan .It is observed that the beaker placed infront fan cools faster .explain the reason

The distance- time graph of a car isas shown in the figure. Is the car moving with constant speed? Find the speed of the car at the end of 2 hour and 6 hour, respectively,

Electric heater works on the basis of "_______" the electric current.

The sounds of frequencies greater than 20 kHz are called ultrasonic sounds.

A boy goes to a shop, which is 3 km away, buys things and comes back. What is the distance and displacement in km and m?

Choose the correct statement : When a positively charged body is placed on the ground. (A) the electrons flow from the ground and neutral-ize the charge. (B) the electrons flow from the ground and charge it negatively.

An empty bottle weighs 30 g. It weighs 54 g when filled with kerosene. If the volume of the bottle is 30 mL, find the density of kerosene in g//cm^(3) and in kg//m^(3)

Fill in the blanks The process of changing a substance from gaseous state to liquid state is called_______.

An electromagnet with soft iron core is a temporary magnet.

Magenta, cyan and yellow are the......... colours.

The direction of light can be changed by ______

{:(,"Column A",,, "Column B"),(A., anglei = angler, (), a., 0.1 s),(B., "Persistence of hearing", ( ), b., "Infrasonic"),(C., "Dolphins", ( ), c., "Law of reflection of sound"),(D., "Carpets", ( ), d., "Echoes"),(E., 10 Hz, (), e., "Reduce noise pollution"):}

What is maximum - minimum thermometer ?

The temperature of a body rises by 1^@C. What is the corresponding rise on the Fahrenheit scale

Two Cars A and B move on a stright road for the same time. Car A covers 80 , and car b covers 100m. Which one of the two is faster ?

Sriharsha had adoublt as towhy the head of a screw drives is made of plastic material and not metal. Clarify his doubt.

Two astronauts who land on the moon cannot talk with each other. What could be the reason for this ? Suggest a method for them to talk each other.

An object moving along a straight line with a constant speed is said to be in _____

For each of theequation four choices have been provided. select the correct alternative On heating a substance which of the following physical quantities changes?

Assertion (A): A rianbow is formed when white light is inicdent on raindrops. Reason (R): White light contains seven colours and it undergoes dispersion inside a raindrop.

During a thunderstorm, the thunder is heard 2.5 seconds after the flash of lightning is seen. If the speed of sound is 330 m s^(-1)find the distance at which lightning took place.

Give an example where translatroy and rotatory motion occurs simultaneously .

The farmer controls the direction of the plough and depth of the soil ploughed, by the __________

Rama watched in discovery channel that ini outer space, at greater heights above the surface of the Earth where atmosphere does not exist appears completely dark. Explain what would be the reason for this?

The velocity of sound is maximum in ______

______ mirror is used as shaving mirror.

A block is 8 cm long, 2 cm wide, and 3 cm high and has a mass 375 g. What is its density?

Our body is a conductor of electricity.

As the temperature of the gas decreases, its density_____.

__________ is used to cut thin sheets of metal

Image of an object in a convex mirror is

Read the following statements and choose the correct option. (A) Onlly a point source forms a complete umbra. (B) An extended source forms a complete umbra and penumbra.

A light ray is incident along the principal axis of a mirror after reflection ______.

No medium is required for transferof heat by the process of convection

The vibratory motion of a tuning fork is ________ in nature.

What is an odometer and a speedometer gt

What is a seconds pendulum ? What is its approximate length ?

Answer the following question What are the animals and plants living in polar region?

Heat in a liquid is transferred by :

A man standing in front of a plane mirror finds his image to be at a distance of 6 metre from himself. The distance of man from the mirror is :

{:(,"Column A",,, "Column B"),(A., "Piano", (), a., "Percussion instrument"),(B., "Mridangram", ( ), b., "Stringed instrument"),(C., "Shehnai", ( ), c., "Reflection of sound"),(D., "Sonar", ( ), d., "Ghana vadya"),(E., "Jal tarang", (), e., "Wind instrument"):}

Electricity does not flow through:

The sound of loudness of sound in the range of 15 dB - 16 dB is

Which of the following is a good conductor of electricity.

For each of theequation four choices have been provided. select the correct alternative Normal temperature of the human body is _________.

One form of energy cannot be converted into another form. True/False.

A Kelvin scale reads temperature to be 318 K. What is the temperature in ""^@C and in ""^@F?

The loudness of sound ________ with increase in the energy spent to vibrate a body.