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UPSC NDA NA (II) Exam 2017: General Science Practice Questions – Physics

Jun 6, 2017 10:35 IST

    For the benefit of UPSC NDA & NA (II) 2017 Exam aspirants, we are providing practice questions for the General Knowledge Section of the General Ability Test. This practice set consists of 10 Questions on Physics. At the end, correct answers with explanations are also given.

    1. Cryogenic engines find applications in :

    (a) sub-marine propulsion

    (b) frost-free refrigerators

    (c) rocket technology

    (d) researches in superconductivity

    2. The clouds float in the atmosphere because of low :

    (a) temperature              

    (b) velocity

    (c) pressure

    (d) density

    3. Given below are two statements, one labelled as Assertion (A) and other labelled as Reason (R)

    Assertion (A) : A diamond sparkles more than a glass imitation cut to the same shape.

    Reason (R) : The refractive index of diamond is less than that of glass.

    In context of the above two statements, which one of the following is correct ?

    (a) Both A and R are true and R is the correct explanation of A

    (b) Both A and R are true and R is not a correct explanation of A

    (c) A is true but R is false

    (d) A is false but R is true

    4. An air bubble in water will act like a ;

    (a) convex mirror            

    (b) convex lens

    (c) concave mirror          

    (d) cancave lens

    5. When a mirror is rotated by an angle 0, the reflected ray will rotate by :

    (a) 0°    

    (b) 0/2

    (c) 0      

    (d) 20

    6. Total internal reflection can take place when light travels from :

    (a) diamond to glass

    (b) water to glass

    (c) air to water 

    (d) air to glass

    7. Given below are two statements, one labelled as Assertion (A) and the other labelled as Reason (R). Assertion (A) : Transformer is useful for stepping up or stepping down voltages.

    Reason (R) : Transformer is a device used in D.C. circuits.

    In the context of the above two statements, which one of the following is correct ?

    (a) Both A and R are true and R is the correct explanation of A

    (b) Both A and R are true but R is not a correct explanation of A

    (c) A is true but R is false

    (d) A is false but R is true

    8. When the frequency distribution is normal :

    (a) median, mode and mean are all different from one another

    (b) mean, mode and median are identical

    (c) mean is greater than mode

    (d) mean is greater than median

    9. Domestic electrical wiring is basically a :

    (a) series connection

    (b) parallel connection

    (c) combination of series and parallel connections

    (d) series connection within each room and parallel connection elsewhere

    10. Consider the following statements :

    At the present level of technology available in India, solar energy can be conveniently used to

    1. Supply hot water to residential buildings.

    2. Supply water for minor irrigation projects.

    3. Provide street lighting.

    4. Electrify a cluster of villages and small towns.

    (a) 1, 2, 3 and 4 are correct

    (b) 2 and 4 are correct

    (c) 1 and 3 are correct

    (d) 1, 2 and 3 are correct

    Answers with Explanations

    1. (c) Cryogenic engines find applications in rocket technology.

    2. (a) When air rises, it is cooled by expansion. After dew point has reached cooling leads to condensation of water vapour in the atmosphere. Tiny droplets of water vapour which are too small to fall as raize or shower will be suspended in the air and float as clouds.

    3. (c) The refractive index of diamond is very high  (approximately 2.47) while the refractive index for  the glass is 1.57. Therefore, the initial angle for the ray of light traveling form diamond to air is very low about 24°. The initial angle for the ray of light traveling from glass to air is 39°. Moreover the diamonds are usually cut with their faces in such a manner that once a ray of light enters into it, it suffers a large number of total internal reflections at various faces till the angle of incidence inside the diamond remains greater than the critical angle. In total internal reflection 100% of the light reflected back into the same medium. Hence, the object shines. That's why a diamond sparkles more than a glass imitation cut to the same shape.

    4.(d)

    5. (d) For given incident ray, if a plane mirror is rotated through a certain angle, then the reflected ray rotates through twice of that angle . So if a mirror is rotated by an angle 0, the reflected ray will rotate by 20.

    6. (a) Total internal reflection takes place when light travels from optically denser medium to optically rarer medium. (Refractive index for diamond = 2.45, refractive index for glass = 1.57)

    7. (c) Assertion A is true but reason R is false. Because a transformer is a device that enables us to step up or step down a given A.C. voltage according to our requirement. A transformer can not work or can not be used with a direct current (D.C.) as it's working is based on the change of magnetic flux with a varying current. Thus, it works only when input is alternating.

    8.(b) When the frequency distribution is normal median, mode and mean are all identical

    9.(b) Domestic electrical wiring is basically a' parallel connection. In parallel circuit each branch receives equal current. In parallel connection if one of the bulbs is removed from the circuit, i.e., if one of the branches in the circuit is broken, electric current will still flow in other branches and other bulbs will continue to glow.

    10. (c) At present level solar energy can be conveniently used to provide street lighting and supply hot water to residential buildings.

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