Physics GK Quiz-30

Physics GK Quiz-30

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

    581. Gas thermometers are more sensitive than the liquid thermometers because the gases

    (1) have large coefficient of expansion
    (2) are lighter
    (3) have low specific heat
    (4) have high,specific heat
    Answer:
    581. (1) Gases are more sensitive to the temperature than liquids (such as mercury). That means gas expands more than the mercury for the same increase of temperature. Hence the gas thermometer is more sensitive than liquid (mercury) thermo-meter.

    582. A man standing on a edge of a cliff throws a stone vertically upwards with a certain speed. He then throws another stone downwards with the same speed. Find the ratio of the speeds of the two stones when they hit the ground.

    (1) 1 : 1
    (2) 1 : 2
    (3) 1 : 4
    (4) Cannot be found from the given information.
    Answer:
    582. (1) The stone which is throws upward will have the same velocity of u at the point of its original position when it is falling down. Another stone is thrown downwards with u. So the velocity of both the stones is equal at the original point. Hence both stone will hit the ground with same velocity. So the ratio between the speeds of two stones will be 1:1

    583. Dioptere is the unit of

    (1) power of a lens
    (2) focal length of a lens
    (3) light intensity
    (4) sound intensity
    Answer:
    583. (1) A dioptre or diopter, is a unit of measurement of the optical power of a lens or curved mirror, which is equal to the reciprocal of the focal length measured in metres (that is, 1/metres). It is thus a unit of reciprocal length.

    584. When a stone is thrown in the calm water of a pond the waves produced on the surface of water in the pond are

    (1) longitudinal
    (2) transverse
    (3) both longitudinal and transverse
    (4) waves are not produced
    Answer:
    584. (2) The waves produced on the surface of water in the pond is an example of transverse waves as particles of the medium do not move along with the wave. Only the disturbance is carried forward. Another example of such waves is the vibrations of a string.

    585. In a filament type light bulb most of the electric power consumed appears as

    (1) visible light
    (2) infra-red rays
    (3) ultra-violet rays
    (4) fluorescent light
    Answer:
    585. (2) When electricity is passed through the filament, the filament gets hot. Depending on the temperature of the filament, radiation is emitted from the filament. The filament’s temperature is very high, generally over 2,000°C. At this high temperature of 2,000°C, about 5 percent of the electrical energy converts into visible light and rest of it is emitted as heat or infrared radiation.

    586. A white and smooth surface is

    (1) good absorber and good reflector of heat
    (2) bad absorber and good reflector of heat
    (3) good absorber and bad reflector of heat
    (4) bad absorber and bad reflector of heat
    Answer:
    586. (2) Shiny surfaces are poor absorbers of heat radiation and the best reflectors of heat radiation. Black surfaces are the best emitters and best absorber of heat radiation.

    587. When a body is immersed in a liquid, the force acting on it is

    (1) Upthrust
    (2) Weight
    (3) Mass
    (4) Both (1) and (2)
    Answer:
    587. (4) According to the Principle of Flotation, when a body is immersed in a fluid, two forces act on it: (1) The weight of the body acting vertically downward through the centre of gravity of the body, and (2) The upthrust of the fluid acting vertically upward through the centre of gravity of the fluid displaced, i.e., centre of buoyancy. The upthrust is also termed as buoyant force.

    588. When two semiconductors of pand n-type are brought in contact, they form p-n junction which acts like a/an

    (1) Conductor 
    (2) Oscillator
    (3) Rectifier 
    (4) Amplifier
    Answer:
    588. (3) P-n junction is a device which flows current in one direction when it is forward biased and when it is reverse biased it doesn’t flow any current through it. So it acts as an rectifier device to convert sinusoidal current to uni-direction. 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.

    589. The mass of a body measured by a physical balance in a lift at rest is found to be m. If the lift is going up with an acceleration a, its mass will be measured as

    (1) m 1
    (2) m 1
    (3) m 
    (4) zero
    Answer:
    589. (3) Mass is the quantity of matter possessed by a body. It will be the same even if the lift goes up with acceleration.

    590. Ohm’s law is valid in case of

    (1) semiconductor
    (2) conductor
    (3) superconductor
    (4) insulator
    Answer:
    590. (2) Ohm’s law states that the current through a conductor between two points is directly proportional to the potential difference across the two points. It defines the relationship between the three fundamental electrical quantities: current, voltage, and resistance.

    591. The Laser is a beam of radiations which are

    (1) Non-coherent and monochromatic
    (2) Coherent and monochromatic
    (3) Non-coherent and non-monochromatic
    (4) Coherent and non-monochromatic
    Answer:
    591. (2) Laser, an acronym for Light Amplification by Stimulated Emission of Radiation, creates a radiation beam that is coherent (in-phase). In a coherent light source, the amplitude of the radiated waves is added and results in a radiation beam of great intensity. It normally produces only one or two wavelengths. The single wavelength is called monochromatic radiation.

    592. Centigrade and Fahrenheit temperatures are the same at

    (1) 32° 
    (2) 40°
    (3) –273° 
    (4) –40°
    Answer:
    592. (4) There is one point on the Fahrenheit and Celsius scales where the temperatures in degrees are equal. That is -400 Celsius or Fahrenheit.

    593. The dimensional formula for universal gravitational constant is

    (1) M–1 L3T2 
    (2) M L2T–2
    (3) M–2 
    (4) M–1 L3 T–2
    Answer:
    593. (4) Universal Constant of Gravitation is represented by G and is derived from Newton’s law of gravitation.

    594. Rocket works on the principle of

    (1) Newton's Third Law
    (2) Newton's First Law
    (3) Newton's Second Law
    (4) Archimedes Principle
    Answer:
    594. (1) The modern science of spaceflight and rockets rest on Newton’s Three Laws of Motion, a set of ideas and equations developed in the 1600s. In particular, the Third Law, which relates the action and reaction of forces, is essential to explain how a rocket accelerates. To make a rocket move forward, its engines point rearward. The action of the engine thrust produces a reaction on the rocket, accelerating it.

    595. The weight of a body acts through the centre of

    (1) gravity
    (2) mass
    (3) both (1) and (2)
    (4) buoyancy
    Answer:
    595. (1) The centre of gravity of a collection of masses is the point where all the weight of the object can be considered to be concentrated. The entire weight acts through the center of gravity instead of acting through the individual masses. In a uniform gravitational field (like the field close to the surface of the Earth) the Centres of Gravity and Mass are in exactly the same place.

    596. A wheel-barrow is an example of

    (1) class III lever
    (2) pulley system
    (3) class I lever
    (4) class II lever
    Answer:
    596. (4) In a Type 2 Lever, the load is between the pivot (fulcrum) and the effort. Examples of common tools that use a type 2 lever include: stapler, bottle opener, wheel barrow, nail clippers and nut cracker.

    597. Magnetic keepers are used to protect magnets from :

    (1) Earth’s magnetic field
    (2) effect of other magnets
    (3) self-demagnetization
    (4) demagnetization due to heating
    Answer:
    597. (3) Magnets have a tendency to lose their magnetism when their poles are left bare. This is called self demagnetization. Magnets are, therefore, protected by keeping them in magnetic keepers.

    598. An object which absorbs all colours and reflects none appears:

    (1) white 
    (2) grey
    (3) blue 
    (4) black
    Answer:
    598. (4) A surface that absorbs all colours, reflecting none, is said to be black. Black is not a colour; it absorbs all the colours of the visible spectrum and reflects none of them to the eyes. White is a colour.

    599. The locomotion of insects to the source of light is called :

    (1) Phototropic
    (2) Hydrotropic
    (3) Phototactic
    (4) Thermotactic
    Answer:
    599. (1) The growth or movement of a plant part in response to a source of light is called phototropism. It is most often observed in plants, but can also occur in other organisms such as fungi.

    600. The splitting of white light into its components is due to:

    (1) reflection
    (2) refraction
    (3) transmission
    (4) dispersion
    Answer:
    600. (4) Dispersion is used to separate a beam of white light into its constituent spectrum of colours. This phenomenon leads to rainbow.

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