Physics GK Quiz-38

Physics GK Quiz-38

Physics Multiple Choice Questions (MCQs) Quiz for State and UPSC Civil Services Examinations. Objective Questions on Physics for competitive examinations.

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

    (1) Convection
    (2) Evaporation
    (3) Revolution
    (4) Thermal Expansion
    Answer:
    741. (1) 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).

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

    (1) Ginzburg Landau theory
    (2) London theory
    (3) Resonating valence bond theory
    (4) Quantum field theory
    Answer:
    742. (2) 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.

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

    (1) metre/sec. 
    (2) Sec.
    (3) Para/sec. 
    (4) Parsec
    Answer:
    743. (4) 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.

    744. At boiling point of liquids, its

    (1) Temperature increases
    (2) Atmospheric pressure increases
    (3) Temperature remains constant
    (4) Vapour pressure decreases
    Answer:
    744. (3) 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.

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

    (1) Mercury is a metal
    (2) Density of mercury is greater than that of water
    (3) Cohesion of mercury is greater than its adhesion with glass
    (4) Cohesion of water is greater than its adhesion with glass
    Answer:
    745. (3) 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.


    746. Which of the following is an insulator?

    (1) Mercury 
    (2) Carbon
    (3) Germanium
    (4) Glass
    Answer:
    746. (4) 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.


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

    (1) Effervescence
    (2) Surface Tension
    (3) Surface Energy
    (4) Degasification
    Answer:
    747. (1) 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.


    748. The boiling point of water depends upon the

    (1) atmospheric pressure
    (2) volume
    (3) density 
    (4) mass
    Answer:
    748. (1) 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.

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

    (1) Reflection 
    (2) Interference
    (3) Diffraction 
    (4) Polarisation
    Answer:
    749. (4) 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.

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

    (1) Ammeter
    (2) Galvanometer
    (3) Rectifier 
    (4) Transformer
    Answer:
    750. (3) 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.

    751. Why does ice covered in sawdust not melt quickly ?

    (1) Sawdust does not allow the air to touch the ice
    (2) The water is absorbed by sawdust
    (3) Sawdust is a bad conductor of heat
    (4) Sawdust is good conductor of heat
    Answer:
    751. (3) Ice needs to absorb heat energy to melt and become water (called latent heat of fusion). Since sawdust is a poor conductor of heat, it takes more time for the ice to absorb the required heat energy. This allows ice to remain in solid state for more time when packed in saw dust.

    752. The washing machine works on the principle of

    (1) Dialysis 
    (2) Diffusion
    (3) Reverse osmosis
    (4) Centrifugation
    Answer:
    752. (4) Washing machines work on the principle of centrifugation. They are based on medium sized centrifuges that put an object in rotation around a fixed axis, applying force perpendicular to the axis. It uses the sedimentation principle, where the centripetal acceleration separates substances of greater and lesser density. Besides, it also makes use of the centrifugal force generated in the “spin cycle” of washing machines that throws the water out through the little holes of perforated drum so that the washed clothes end up much drier.

    753. The ‘Choke’ used with a tube light is basically

    (1) an inductor
    (2) a capacitor
    (3) a transformer
    (4) a resistor
    Answer:
    753. (1) In electronics, a choke is an inductor used to block higher-frequency alternating current (AC) in an electrical circuit, while passing lower-frequency or direct current (DC). In a tubelight, the high voltage is created by suddenly interrupting the current in choke, which is connected in series with the tubelight. 

    754. Curie is an unit of

    (1) Radioactivity
    (2) energy of Gamma rays
    (3) intensity of Gamma rays
    (4) work function
    Answer:
    754. (1) The curie (symbol Ci) is a non-SI unit of radioactivity, named ‘in honour of’ Pierre Curie. It was originally defined as “the quantity or mass of radium emanation in equilibrium with one gram of radium (element)”, but is currently defined as: 1 Ci = 3.7 × 1010 decays per second after more accurate measurements of the activity of 226Ra.

    755. Energy travels from Sun to Earth through

    (1) conduction
    (2) convection
    (3) radiation
    (4) modulation
    Answer:
    755. (3) Solar energy, in the form of heat and light, travels from the sun to Earth through the process of radiation. This way, energy can be transferred through empty space without relying on matter. This radiation is largely visible as light to the naked eye, although it also includes ultraviolet and infrared radiation as well.

    756. Heat is transmitted from higher temperature to lower temperature through the actual motion of the molecules in

    (1) Conduction
    (2) Convection
    (3) Radiation
    (4) Both conduction and convection
    Answer:
    756. (2) The process of heat transfer from one place to another place without the movement of particles is called conduction Example:Heat transfer through Metal rods. On the contrary, convection is the process by which heat is transmitted through a substance from a point to another due to the bodily motion of the heated particles of the substance. The fluids (liquids and gases) are heated by this process.


    757. Which one among the following components is used as an amplifying device?

    (1) Transformer
    (2) Diode 
    (3) Capacitor
    (4) Transistor
    Answer:
    757. (4) An amplifier is an electronic device that increases the voltage, current, or power of a signal.Generally transistors are active devices that can be used with discrete components to amplify voltage, power or both depending upon the configuration.

    758. The unit of measurement of noise is

    (1) Decibel 
    (2) Hertz
    (3) Amplifier 
    (4) Acoustics
    Answer:
    758. (1) The decibel (dB) is the unit used to measure the intensity of sound or noise level. It is given in terms of a logarithmic function of a ratio of power intensities. One decibel is one tenth of one bel, named in honor of Alexander Graham Bell who was the inventor of the telephone and phonograph.

    759. The commonly used coolant in refrigerators is

    (1) Ammonia 
    (2) Nitrogen
    (3) Freon 
    (4) Oxygen
    Answer:
    759. (3) Modern refrigerators usually use a refrigerant called HFC-134a (1,1,1,2-Tetrafluoroethane), which does not deplete the ozone layer, instead of Freon. Freon used to be the most common refrigerant till the 1980s; however, its use has declined since the 1990s because it comes under Chlorofluorocarbon (CFC). Ammonia was also used a a common refrigerant in old refrigerators. However, Freon still remains the most commonly used refrigerant. Hydrochlorofluorocarbon (HCFC), is a type of refrigerator coolant used in newer refrigerator models. The types used today include HFC-134a, HCFC-142b and HCFC-22.

    760. A galvanometer can be converted into a voltmeter by connecting with it a

    (1) high resistance in parallel
    (2) low resistance on parallel
    (3) high resistance on series
    (4) low resistance in series
    Answer:
    760. (3) In order to convert a Galvanometer into voltmeter, a very high resistance known as “series resistance” is connected in series with the galvanometer. The conversion is made for enabling the galvanometer to measure the potential difference across any component in a circuit.

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