WBCS Preliminary Exam Solved Question Paper 2004 (Science) - WBCS Online Portal for Self Studies

Q1. The temperature of two bodies being equal means

(A) Their heat contents are the same

(B) When they are brought in contact there will be no exchange of heat

(C) Their heat capacities are the same

(D) Their specific heats are the same

  • When two bodies at different temperatures T1 and T2 are brought in thermal contact, heat flows from the body at the higher temperature to the body at the lower temperature till equilibrium is achieved.

Q2. When a helium atom loses an electron, it is converted to a

(A) Proton (b) Alpha-particle (C) Deuteron (D) Helium ion

  • When helium loses  1 electron it becomes a positive helium ion.
  • When helium loses 2 electrons it becomes alpha particle.

Q3. If the length and cross-section of a wire are both doubled the resistance will

(A) increased times (B) decreases 4 times (C) increase twice (D) remain unchanged

  • Resistance is proportional to (Length / Cross-section Area).

Q4. In simple harmonic motion the kinetic energy

(A) is never zero (B) becomes zero twice in every period

(C) is zero in the mean position (D) is always constant

Q5. What is stored in a storage cell?

(A) Electric charge (B) Electric potential (C) Lead or some other metal (D) Chemical energy

  • Delivers electric current as the result of a chemical reaction. Eg. Battery.

Q6. 10 gm of ice at 0°C is mixed with 10 gm of water at 10°C. The temperature of the mixture will be

(A) l°C   (B) 5°C   (C) 10°C   (D) 0°C

Q7. The specific resistance of a conductor depends on its

(A) length (B) width (C) temperature (D) shape of the cross-section

  • ‘Specific resistance’ means the resistance offered by a unit length and a unit cross-section of the conductor to a current when a voltage is applied to it.
  • Specific resistance depends upon nature of material & Temperature. Length & cross-section both are one unit here.
  • ‘Resistance’ is directly proportional to length of conductor and inversely proportional to the cross-sectional area of it. —#Link

Q8. When a ship enters the sea from a river, it floats up because

(A) Sea water is warmer (b) the speed of the ship on the sea is greater

(c) the density of the river water is greater (d) salt water of the sea is denser

Q9. A raindrop falls in and with an uniform velocity

(A) its potential energy remains constant 

(B) its mechanical energy is conserved

(C) its mechanical energy is being transferred of the atmosphere 

(D) the total energy of the drop and air decays

  • A raindrop after falling through some height attains a constant velocity.

Q10. Mass of a body is defined by the following quantity

(A) velocity/acceleration (B) applied force/velocity

(C) applied force/acceleration (D) applied force/increase in momentum

  • As per Newton’s second law, F=ma, which means the force (F) acting on an object is equal to the mass (m) of an object times its acceleration (a). This means the more mass an object has, the more force you need to accelerate it. And the greater the force, the greater the object’s acceleration.

Q11. The period of rotation of an artificial earth satellite

(A) depends on its distance from the earth’s surface

(B) is proportional to its distance from the earth’s centre

(C) is inversely proportional to its mass

(D) 24 hours

  • A geosynchronous satellite is a satellite that orbits the earth with an orbital period of 24 hours, thus matching the period of the earth’s rotational motion. A special class of geosynchronous satellites is a geostationary satellite. A geostationary satellite orbits the earth in 24 hours along an orbital path that is parallel to an imaginary plane drawn through the Earth’s equator. Such a satellite appears permanently fixed above the same location on the Earth.  — #Link

Q12. The only vector quantity among the following is

(A) electric charge (B) electric potential

(C) electric field intensity (D) electric resistance

Q13. If a magnet is moved fast towards a coil, the induced electromotive force does not depend on

(A) the number of turns of the coil (B) pole strength of the magnet

(C) the speed of the magnet (D) the resistance of the coil

Q14. In a p-type semiconductor, which is the main carrier of electricity?

(A) Positive holes (B) positive ions (C) Electrons (D) Negative ions

  • In n-type semiconductors, electron is the main carrier.

Q15. A ball is dropped from a given height. If its collision with the ground is fully elastic, it will reach a height

(A) less than before (B) same as before (C) more than before (D) height will not depend on elastic

  • Each time it will achieve the same height & will never come to rest.

Q16. Which of the following is different from the others?

(A) Cathode rays (B) Photo electrons (C) alpha-rays (D) Thermal electrons

  • Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus). 
  • All the other options are related to emission of electrons; not radioactive decay. 

Q17. The current on a 100W, 220V electric bulb is

(A) 2.2 amp. (B) 1.1 amp.
(C) 5/11 amp. (D) 22000 amp

Q18. The first Herbal anti-AIDS drug ‘Herbtab’ will be marketed in India by

(A) Veronica Lab (B) Dr. Reddy Lab (C) Ranbaxy Lab (D) Astra Zeneca

Q19. The magnetic length of a bar magnet means

(A) its total length (B) The distance between its two poles

(C) its width (D) the distance of a pole from the centre

Q20. A rocket leaves the earth, lands on the moon and returns to earth. It will require the maximum energy to

(A) rise from the earth (B) land on the moon

(C) rise from the moon (D) land on the earth

  • The amount of energy a rocket must expend to go from Earth’s surface to low-Earth orbit above is almost thrice as much as the energy needed to go from there to the Moon. —#Link

Q21. The production of shadow proves that

(A) light travels approximately in straight lines (B) light is an electromagnetic wave

(C) light is a type of particle (D) light docs not diffract

  • Once light has been produced, it will keep travelling in a straight line until it hits something else. Shadow is the evidence of light travelling in straight lines. —#Link

Q22. A bimetallic strip of iron and brass bends while heated because

(A) iron and brass have different specific heats

(B) their coefficients of linear expansion are different

(C) While heated their temperatures become different

(D) iron and brass become soft when heated

  • If two rods of different metals have same length L at temperature t1°C, their length at higher temperature t°C will be different. The rod of a metal having more value of ‘ coefficient of linear expansion will have more length than the other rod. In case of an iron-brass bi-metallic strip, brass will have more length at higher temperature. —#Link

Q23. A piece of stone to a string is being rotated in a vertical plane with constant angular velocity. The tension of the string will be maximum when

(A) the stone is in the highest position (B) the stone is in the lowest position

(C) the string is horizontal (D) the tension is always the same

  • The tension in the lowest position is maximum and tension in the highest position is minimum. — #Link

Q24. A magnifying glass or a simple microscope produces a

(A) magnified real image

(B) virtual image near the eye, having the same size as the object

(C) magnified virtual image

(D) diminished virtual image

  • The light is refracted and focused by the lens to produce a virtual image on the retina. The image is magnified because we perceive the actual size of the object to be at infinity because our eyes trace the light rays back in straight lines to the virtual image.

Q25. If red light used to illuminate a green leaf and a red flower, it will appear as

(A) Green leaf and red flower (B) red leaf and red flower

(C) Black leaf and red flower (D) black leaf and black flower

Q26. In the solar spectrum Fraunhofer lines are seen in the sodium D wavelength This proves

(A) there is no sodium in the sun (B) there is no sodium in the solar atmosphere

(C) there is no sodium in sun’s interior (D) there is sodium in the solar atmosphere

  • The Fraunhofer lines are a set of famous absorption lines named after a German physicist. Fraunhofer designated the principal features with the letters A through K from longer wavelength (redder) to shorter (bluer). For example, the D line is caused by sodium, and the H and K lines are caused by calcium. — #Link

Q27. Which of the following colours does not match the sequence?

Violet, Brown, Green, Red

(A) Green (B) Red (C) Brown (D) Violet

The Resistor Colour Code sequence —

Black >> Brown >> Red >> Orange >> Yellow >> Green >> Blue >> Violet >> Grey >> White >> Gold >> Silver.    — #Link

The Visible Light Spectrum —

Red (highest wavelength, 625 – 740 nm) >> Orange >> Yellow >> Green >> Cyan >> Blue >> Violet.   —#Link

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