Physics GK Quiz-37

Physics GK Quiz-37

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

    721. Alcohol is more volatile than water because _________ is lower than water.

    (1) its boiling point
    (2) its density
    (3) its viscosity
    (4) its surface tension
    Answer:
    721. (1) Drinking alcohol (ethanol) and a lot of other simple alcohols are more volatile than water because they are less polar. Thus, alcohol has higher vapor pressure and a lower boiling point than water; therefore, it evaporates more quickly. Its low boiling point of 78o C is what makes it possible to distill alcohol into a much stronger solution than wine or beer.

    722. Which of the following is the second largest source of global energy?

    (1) Fossil fuel
    (2) Nuclear Energy
    (3) Renewable Energy
    (4) None of these
    Answer:
    722. (3) Data for 2013 shows that renewable electricity generation overtook natural gas to become the second largest source of electricity worldwide producing 22% of total electricity or 5,130 TWh. Some of the sources of renewable energy are: solar power, wind power, wave and tidal power, geothermal power, biomass and hydro power. Fossil fuels remained the bedrock of global electricity production with more than two-thirds (about 67%) of the total.

    723. A light year is a unit of:

    (1) Time
    (2) Distance in Space
    (3) Length of astronomical distances
    (4) Distance travelled by light
    Answer:
    723. (*) More than one option is correct. A light-year is a unit of length used informally to express astronomical distances. It is the distance that light can travel in one year which is approximately 9
    trillion kilometres (or about 6 trillion miles). As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in vacuum in one Julian year (365.25 days). Best Option: (4)

    724. The SI unit of luminous emittance is :

    (1) Lux 
    (2) Candela
    (3) Lumen
    (4) Lumen second
    Answer:
    724. (1) The lux is the SI unit of illuminance and luminous emittance, measuring luminous flux per unit area. It is equal to one lumen per square metre. In photometry, this is used as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface.

    725. Which of the following is the unit of perceived loudness of sound ?

    (1) Decibel 
    (2) Sone
    (3) Hertz 
    (4) Phon
    Answer:
    725. (2) Loudness is a subjective characteristic of a sound (as opposed to the sound-pressure level in decibels, which is objective and directly measurable). Perceived loudness of sound is a psycho-acoustic quantity that depends on sound pressure level, the frequency spectrum, and the time behavior of the sound in question. The sone is a unit of perceived loudness that was proposed by Stanley Smith Stevens in 1936.Being a unit of how loud a sound is perceived, the sone scale of loudness is based on data obtained from subjects who were asked to judge the loudness of pure tones and noise. One sone is arbitrarily set equal to the loudness of a 1,000-hertz tone at a sound level of 40 decibels (Encyclopedia Britannica).

    726. Stress can be defined as _____ quantity.

    (1) Scalar 
    (2) Vector
    (3) Phasor 
    (4) Tensor
    Answer:
    726. (4) 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.

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

    (1) weight
    (2) distance
    (3) temperature
    (4) size
    Answer:
    727. (3) 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.

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

    (1) Rectification
    (2) Amplification
    (3) Modulation
    (4) Filtration
    Answer:
    728. (1) 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.

    729. Which term is not associated with sound wave?

    (1) Hertz 
    (2) Decibel
    (3) Candela 
    (4) Mach
    Answer:
    729. (3) 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.

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

    (1) velocity
    (2) linear momentum
    (3) angular momentum
    (4) energy
    Answer:
    730. (2) 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.

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

    (1) remain same
    (2) double
    (3) three times
    (4) four times
    Answer:
    731. (2) 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.

    732. 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:

    (1) 8 T 
    (2) 4 T
    (3) 2 2 T 
    (4) 2 T
    Answer:
    732. (1) 

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

    (1) half the weight at the surface
    (2) zero
    (3) twice the weight at the surface
    (4) infinite
    Answer:
    733. (2) 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.

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

    (1) It lowers
    (2) It sways
    (3) It rises a little
    (4) It jolts
    Answer:
    734. (3) 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.

    735. Hydroscope is an instrument that shows changes in:

    (1) Sound under water
    (2) Atmospheric humidity
    (3) Density of liquid
    (4) Elevation of land
    Answer:
    735. (*) 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.

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

    (1) Sand desert
    (2) Land covered with fresh snow
    (3) Prairie land
    (4) Paddy crop land
    Answer:
    736. (2) 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%

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

    (1) Avogadro’s law
    (2) Rault’s law
    (3) Ohms law
    (4) Faraday’s law
    Answer:
    737. (3) 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 µ I or V = I × R or I = V R or R = V I

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

    (1) 21-A 
    (2) 46
    (3) 39 
    (4) 15
    Answer:
    738. (1) 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.

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

    (1) Hot air replacement
    (2) Air dehydration
    (3) Evaporative Cooling
    (4) Air Rehydration
    Answer:
    739. (3) 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.

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

    (1) Earth spinning on its axis
    (2) Simple pendulum motion
    (3) Ball bouncing on floor
    (4) Motion of a ceiling fan
    Answer:
    740. (2) 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.

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