# Physics GK Quiz-21

## Physics GK Quiz-21

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

### 401. The important unit of a microprocessor is

(1) ALU
(2) array of registers
(3) control unit
(4) All of the above
401. (4) The basic units or blocks of a microprocessor are ALU, an array of registers and control unit. A minimal hypothetical microprocessor might only include an arithmetic logic unit (ALU) and a control logic section. Each operation of the ALU sets one or more flags in a status register, which indicate the results of the last operation (zero value, negative number, overflow or others).

### 402. Anemometer is used to measure

(1) wind direction
(2) wind velocity
(4) wind speed and time
402. (2) An anemometer is a device for measuring wind speed, and is a common weather station instrument. The first known description of an anemometer was given by Leon Battista Alberti around 1450.

### 403. Which one of the following has the highest value of specific heat?

(1) Glass
(2) Copper
(4) Water
403. (4) The specific heat of water is 1 calorie/gram °C = 4.186 joule/gram °C which is higher than any other common substance. As a result, water plays a very important role in temperature regulation.

### 404. The device used for locating submerged objects under sea is.

(1) sonar
(3) laser
(4) maser
404. (1) Sonar (originally an acronym for SOund Navigation And Ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, communicate with or detect objects on or under the surface of the water, such as other vessels. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of “targets” in the water.

### 405. The metal whose electrical conductivity is more, is

(1) copper
(2) aluminium
(3) silver
405. (3) Copper ; 9% less conductive than silver; aluminium is 10% less conductive than copper; while steel is the least conductive among the given options. The most electrically conductive metal is silver.

### 406. What happens to a liquid, when the vapour pressure equals the atmospheric pressure?

(1) The liquid cools
(2) The liquid boils
(3) No change
(4) The liquid evaporates
406. (2) Ordinary evaporation is a surface phenomenon - since the vapor pressure is low and since the pressure inside the liquid is equal to atmospheric pressure plus the liquid pressure, bubbles of water vapor cannot form. But at the boiling point, the saturated vapor pressure is equal to atmospheric pressure, bubbles form, and the vaporization becomes a volume phenomena.

### 407. In nuclear reactor, heavy water is used as

(1) coolant
(2) fuel
(3) moderator
(4) atomic smasher
407. (3) Heavy water is used in certain types of nuclear reactors where it acts as a neutron moderator to slow down neutrons so that they are more likely to react with the fissile uranium-235 than with uranium-238 which captures neutrons without fissioning. Because they do not require uranium enrichment, heavy water reactors are of concern in regards to nuclear proliferation.

### 408. Tear gas used by the police to disperse the mob contains

(1) carbon dioxide
(2) chlorine
(3) ammonia
(4) hydrogen sulphide
408. (2) Tear gas is a compound. Each molecule of tear gas contains one atom of chlorine. The compound 2- chlorobenzalmalononitrile, a cyanocarbon, is the defining component of a “tear gas” commonly referred to as CS gas, which is used as a riot control agent.

### 409. Water boils at a lower temperature on the hills because

(1) it is cold on the hills
(2) there is less carbon dioxide on the hills
(3) there is a decrease in air pressure on the hills
(4) There is less oxygen
409. (3) Water boils at a lower temperature on top of a mountain because there is less air pressure on the molecules. Water boils when the vapor pressure of water exceeds atmospheric pressure. Because the
boiling temperature is lower at high elevations foods that are cooked by boiling take a little longer to cook at high elevation.

### 410. Why do brids not have respiratory trouble at the time of flying at high altitude ?

(1) Their lungs are very large
(2) They fly inactively
(3) They have extra air sacs
(4) They use less oxygen
410. (3) The avian respiratory system delivers oxygen from the air to the tissues and also removes carbon dioxide. In addition, the respiratory system plays an important role in thermoregulation (maintaining normal body temperature). The avian respiratory system is different from that of other vertebrates, with birds having relatively small lungs plus nine air sacs that play an important role in respiration (but are not directly involved in the exchange of gases).

### 411. The temperature which has the same reading on both Fahrenheit and Celsius scales is

(1) 40°
(2) –40°
(3) –34°
(4) –140°
411. (2) If C is the temperature in Celsius and F is the temperature in Fahrenheit then, They are equal at -40° (minus 40 degrees), because if we convert the readings of Celsius and Fahrenheit, we will have:
Celsius to Fahrenheit (-40°C x 9/5) +32 = -72 + 32 = -40°F. Fahrenheit to Celsius (-40°F - 32°) x 5/9 = (-72) x 5/9 = -40°C.

### 412. Kilowatt -hour is the unit of :

(1) Energy
(2) Power
(3) Force
(4) Momentum
412. (1) The kilowatt hour, or kilowatt-hour, is a unit of energy equal to 1000 watt hours or 3.6 mega-joules For constant power, energy in watt hours is the product of power in watts and time in hours. The
kilowatt hour is most commonly known as a billing unit for energy delivered to consumers by electric utilities.

### 413. The part of the eye having the larges refractive index is :

(1) cornea
(2) aqueous humor
(3) lens
(4) vitreous humor
413. (3) The cornea represents the strongest part of the refracting power of the eye, providing about 80% of the power of the system. The index of refraction of the cornea is about 1.376. Rays pass from the cornea into the watery fluid known as the aqueous humor which has an index of refraction of about 1.336. The lens provides perhaps 20% of the refracting power of the eye with a refractive index of 1.386-1.406. the refractive Index of Vitreous Humor is 1.33.

### 414. Conversion of heat into electrical er is achieved by using :

(1) Ammeter
(2) Hydrometer
(3) Voltmeter
(4) Thermocouple
414. (4) Thermoelectric generators convert thermal energy into electricity by using heat from the body — or any object with a temperature gradient — as their energy source. At the heart of every thermoelectric generator is an array of thermocouples that are responsible for converting thermal energy into electricity. Bismuth telluride and its alloys are commonly used in thermocouples.

### 415. Ball pen functions on the principle of :

(1) Viscosity
(2) Boyle’s Law
(3) Gravitational force
(4) Surface tension
415. (4) The ballpoint pen is one of the most simple and yet ubiquitous devices whose function depends on surface tension. With a pen held upright, gravity and surface tension act in concert to get ink onto the ball.

### 416. A man cannot see clearly beyond 10 meters. The disease he suffers from :

(1) Far sight
(2) Myopia
(3) Cataract
(4) Hypermetropia
416. (2) The man suffers from myopia, a vision condition in which close objects are seen clearly, but objects farther away appear blurred. Nearsightedness occurs if the eyeball is too long or the cornea, the clear front cover of the eye, has too much curvature. As a result, the light entering the eye isn’t focused correctly and distant objects look blurred.

### 417. When milk is churned, the cream separates from it due to:

(1) Frictional force
(2) Centrifugal force
(3) Gravitational force
(4) Viscous forces
417. (2) The extraction of cream happens because of the work of centrifugal force which works outward. The separation of cream from milk is based on the fact that when liquids of different specific gravities revolve around the same centre at the same distance with the same angular velocity, a greater centrifugal force is exerted on the heavier liquid than on the lighter one. Milk can be regarded as two liquids of different specific gravities, the serum and the fat.

### 418. Moving electric charge produces :

(1) magnetic field
(2) sound waves
(3) light rays
(4) heat waves
418. (1) An electric charge always produces an electric field, regardless of speed, and a moving charge
generates a magnetic field. An electric current passing through a conductor produces a magnetic field
because it has many charges in motion.

### 419- The S.I. unit of electric charge is :

(1) ampere
(2) coulomb
(3) e.s.u
(4) kelvin
419. (2) The SI unit of quantity of electric charge is the coulomb, which is equivalent to about 6.242×1018 e (e is the charge of a proton). Hence, the charge of an electron is approximately -1.602×10-19 C. The coulomb is defined as the quantity of charge that has passed through the cross section of an electrical conductor carrying one ampere within one second.

(1) eraser
(2) grazer
(3) maser
(4) laser