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Part 030 – Physics Previous Year Questions

Q1. Stress can be defined as _____ quantity.
(a) Scalar (b) Vector
(c) Phasor (d) Tensor
Ans: (d) Stress is defined as Resisting force per unit area of an element, on which load is applied. Stress is always perpendicular to a cross-section in the element. It is neither scalar (it cannot be numerically added), nor is it a vector (it does not follow the triangle rule of vector addition). It is a tensor quantity because it describes things happening in two directions simultaneously.

Q2. Which of the following is indicated by the colour of a star ?

(a) weight
(b) distance
(c) temperature
(d) size
Ans: (c) Colour is caused by the temperature of the surface of the star. A star approximates the behavior of a black body radiator. As a black body gets hotter its color changes. Small stars are cool (less than 3000°C) with a reddish appearance, whereas big heavy stars are hot (over 30,000°C), and have a bluish glow.

Q3. For which one of the following, ‘Diodes’ are generally used for?

(a) Rectification
(b) Amplification
(c) Modulation
(d) Filtration
Ans: (a) In electronics, a diode is an electronic device that allows current to flow in one direction only. It is mainly used as a rectifier diode that lets electrical current flow in only one direction and is mainly used for power supply operation. Rectifier diodes are used for changing alternating current into direct current.

Q4. Which term is not associated with sound wave?

(a) Hertz (b) Decibel
(c) Candela (d) Mach
Ans: (c) Candela is the standard unit of luminous intensity, the luminous power per unit solid angle emitted by a point light source in a particular direction, in the International System of Units. The word candela means candle in Latin.

Q5. If an electron and a photon have the same wavelength, then they will have the same

(a) velocity
(b) linear momentum
(c) angular momentum
(d) energy
Ans: (b) When a non-relativistic electron and a non-relativistic proton are moving and have the same de Broglie wavelength, then they will have the same linear momentum p = mv. If the electron and proton have the same momentum, they cannot have the same speed because of the difference in their masses. An electron and photon can have the same wavelength since the wavelength of electron can be changed by changing its velocity.

Q6. When temperature difference between liquid and its surroundings is doubled, the rate of loss of heat will:

(a) remain same
(b) double
(c) three times
(d) four times
Ans: (b) According to Newton’s law of cooling, the rate of loss of heat of a body is directly proportional to the difference between the temperature of hot body and temperature of the surroundings, provided that the difference in temperature is small enough.

Q7. The period of revolution of a certain planet in an orbit of radius R is T. Its period of revolution in an orbit of radius 4R will be:

(a) 8 T (b) 4 T
(c) 6 T (d) 2 T
Ans: (a) Using Kepler’s Third Law, T^2/(T_1^2 )=(R/4R )^3 =1/64 T1 = 8T

Q8. The weight of a body at the centre of earth is:

(a) half the weight at the surface
(b) zero
(c) twice the weight at the surface
(d) infinite
Ans: (b) Weight of a body is the force with which it is attracted towards the centre of earth. The weight of a body, ‘w’ of mass ‘m’ is given by: W = mg, where ‘g’ is the acceleration due to gravity At the centre of earth, value of ‘g’ is zero. Therefore, weight of a body is zero at the centre of the earth.

Q9. When a ship enters the sea from a river what will be the effect?

(a) It lowers
(b) It sways
(c) It rises a little
(d) It jolts
Ans: (c) When a ship enters the sea from a river, it rises a little since salt water is denser than river water. As the density of river water is less than that of the sea water, the water displaced by the ship in the river is more than that displaced in the sea. So it rises as it enters sea from river.

Q10. Hydroscope is an instrument that shows changes in:

(a) Sound under water
(b) Atmospheric humidity
(c) Density of liquid
(d) Elevation of land
Ans: (*) Hydroscope is an optical device for enabling a person to see an object at a considerable distance below the surface of water by means of a series of mirrors enclosed in a steel tube. Hydrophone is an instrument used for recording sound under water. It is the underwater equivalent of a microphone that measures pressure fluctuations, and these are usually converted to sound pressure level (SPL), a logarithmic measure of the mean square acoustic pressure.

Q11. Which one of the following reflects back more sunlight as compared to other three?

(a) Sand desert
(b) Land covered with fresh snow
(c) Prairie land
(d) Paddy crop land
Ans: (b) Albedo is the fraction of solar energy (shortwave radiation) reflected from the Earth back into space. It is a measure of the reflectivity of the earth’s surface. Ice, especially with snow on top of it on land, has the highest albedo. The albedo of given sources is as follows: l Fresh snow or ice: 60-90% or 80-95%; l Desert sand: 30-50%; l Prairie Grasslands: 18-25% or 20%; l Crops: = 10-25%

Q12. The magnitude of current flowing between two end points of a conductor is proportional to the potential difference between them and is called as:

(a) Avogadro’s law
(b) Rault’s law
(c) Ohms law
(d) Faraday’s law
Ans: (c) According to Ohm’s Law, the potential difference (V) between two terminals of a current-carrying conductor is directly proportional to the current (I), flowing through it. The proportionality constant R, is the resistance of the conductor. Thus, V I or V = I × R or I= V/R or R= V/I

Q13. Which Article of the Indian Constitution provides free and compulsory education to children?

(a) 21-A (b) 46
(c) 39 (d) 15
Ans: (a) According to Article 21A of Indian Constitution, theState shall provide free and compulsory education to all children of the age of six to fourteen years in such manner as the State may, by law, determine. This article was inserted in the constitution by 86th Amendment Act, 2002, also known as Right of Children to Free and Compulsory Education Act.

Q14. The cooling by a desert Cooler is based on:

(a) Hot air replacement
(b) Air dehydration
(c) Evaporative Cooling
(d) Air Rehydration
Ans: (c) Nature’s most efficient means of cooling is through the evaporation of water. Desert coolers make use of evaporative cooling that works on the principle of heat absorption by moisture evaporation. As water is evaporated, energy is lost from the air, reducing the temperature. Thus, cooling effect is produced.

Q15. Which of the following is an example of simple harmonic motion?

(a) Earth spinning on its axis
(b) Simple pendulum motion
(c) Ball bouncing on floor
(d) Motion of a ceiling fan
Ans: (b) When a body moves about a mean position in such a way that the acceleration is proportional to the displacement and is always directed towards the mean position, the body is said to execute a simple harmonic motion. The motion of a simple pendulum falls under this category.

Q16. Which of the following are methods of heat transfer?

(a) Convection
(b) Evaporation
(c) Revolution
(d) Thermal Expansion
Ans: (a) Convection is the transfer of heat from one place to another by the movement of fluids. It is usually the dominant form of heat transfer(convection) in liquids and gases. Although often discussed as a distinct method of heat transfer, convective heat transfer involves the combined processes of conduction (heat diffusion) and advection (heat transfer by bulk fluid flow).

Q17. Which of the following was the first theory of super conductivity?

(a) Ginzburg Landau theory
(b) London theory
(c) Resonating valence bond theory
(d) Quantum field theory
Ans: (b) The first phenomenological theory of superconductivity was London theory. It was put forward by the brothers Fritz and Heinz London in 1935, shortly after the discovery that magnetic fields are expelled from superconductors. A major triumph of the equations of this theory is their ability to explain the Meissner effect, wherein a material exponentially expels all internal magnetic fields as it crosses the superconducting threshold.

Q18. Which of the following is the unit of Astronomical Distance ?

(a) metre/sec. (b) Sec.
(c) Para/sec. (d) Parsec
Ans: (d) A parsec is a unit of length used to measure large distances to objects outside our Solar System. One parsec is the distance at which one astronomical unit subtends an angle of one arc second. A parsec is equal to about 3.26 light-years in length.

Q19. At boiling point of liquids, its

(a) Temperature increases
(b) Atmospheric pressure increases
(c) Temperature remains constant
(d) Vapour pressure decreases
Ans: (c) An interesting property of matter is that its temperature remains constant during a phase change, assuming its surrounding pressure is constant. A liquid changes into gaseous state at a constant temperature called its boiling point. For example, when water is converted into vapors (gaseous state) at 100°C and so 100°C is its boiling point. The temperature remains constant at 100°C. The temperature of water increases only after all the water is evaporated. Likewise, once the temperature of a liquid is lowered to its freezing point, the temperature does not decrease until all the liquid has changed its phase to become a solid.

Q20. On a clean glass plate a drop of water spreads to form a thin layer whereas a drop of mercury remains almost spherical because

(a) Mercury is a metal
(b) Density of mercury is greater than that of water
(c) Cohesion of mercury is greater than its adhesion with glass
(d) Cohesion of water is greater than its adhesion with glass
Ans: (c) When liquid is placed on a smooth surface like glass plate, the relative strengths of the cohesive and adhesive forces acting on that liquid determine the shape it will take (and whether or not it will wet the surface). If the adhesive forces between a liquid and a surface are stronger, they will pull the liquid down, causing it to wet the surface. However, if they cohesive forces among the liquid itself are stronger, they will resist such adhesion and cause the liquid to retain a spherical shape and bead the surface. Mercury drop remains spherical on a plate of glass because its cohesive force is greater than its adhesive force with glass.

Q21. Which of the following is an insulator?

(a) Mercury (b) Carbon
(c) Germanium
(d) Glass
Ans: (d) Insulators are materials that do not allow the transfer or that slow the transfer of heat or electricity. Some of the examples of insulators are: glass, plastic, rubber, porcelain, wood, ceramic, dry air, etc.

Q22. Name the process by which bubbles from liquid are formed?

(a) Effervescence
(b) Surface Tension
(c) Surface Energy
(d) Degasification
Ans: (a) Effervescence is the escape of gas from an aqueous solution and the foaming or fizzing that results from a release of the gas. It leads to the formation of gas bubbles in a liquid. For example, when opening a bottle of champagne, beer or carbonated beverages such as soft drinks, the visible bubbles are produced by the escape from solution of the dissolved gas.

Q23. The boiling point of water depends upon the

(a) atmospheric pressure
(b) volume
(c) density (d) mass
Ans: (a) The boiling point corresponds of water to the temperature at which its vapour pressure equals the surrounding environmental pressure. So it is dependent on theatmospheric pressure. For example, at higher altitudes, the atmospheric pressure decreases. As this pressure decreases, the boiling point of the water also decreases.

Q24. What is the phenomenon which established the transverse nature of light ?

(a) Reflection (b) Interference
(c) Diffraction (d) Polarisation
Ans: (d) The phenomena which proves the transverse nature of light is polarization. Since the intensity of polarized light on passing through a tourmaline crystal changes, with the relative orientation of its crystallographic axes with that of the polarizer, therefore light must consist of transverse waves. Transverse waves are waves that are oscillating perpendicularly to the direction of propagation

Q25. What is the name of the device used to convert alternating current into direct current ?

(a) Ammeter
(b) Galvanometer
(c) Rectifier (d) Transformer
Ans: (c) A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The process is known as rectification.

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