HPSC MCQ Series: Physics-II

# HPSC MCQ Series: Physics-II

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## Physics Multiple Choice Questions For HCS Exam

### Important 20000 MCQ Series For HCS Exam: PHYSICS PART-II

Q1. A person standing on a railway platform listens to the whistles of arriving and departing trains. The whistle heard is

(a) the same in both cases in all respects

(b) of higher intensity when train arrives

(c) of higher pitch when train arrives

(d) of higher pitch when train departs

Ans: (c) of higher pitch when train arrives

Explanation: Sound is a sequence of waves of pressure that propagates through compressible media such as air or water. (Sound can propagate through solids as well, but there are additional modes of propagation). Sound that is perceptible by humans has frequencies from about 20 Hz to 20,000 Hz. In air at standard temperature and pressure, the corresponding wavelengths of sound waves range from 17 m to 17 mm. During propagation, waves can be reflected, refracted, or attenuated by the medium. Now if we consider these cases, then the train which is arriving towards us having whistles of higher pitch because it propagates through a medium which is coming towards us but the train which is leaving propagating through a medium moving further away from the listener and thus produced whistle of lower pitch.

Q2. Holography is a technique of

(a) recording a permanent, sharp two dimensional black and white or multi colour photograph

(b) recording a permanent three dimensional multi colour photograph

(c) recording a permanent three dimensional black and white photograph

(d) recording a permanent three dimensional photograph of a given single colour or a multi colour

Ans:(d) recording a permanent three dimensional photograph of a given single colour or a multi colour

Explanation: Holography is a photographic technique that records the light scattered from an object, and then presents it in a way that appears three-dimensional.

Q3. Boyle’s Law holds good for any gas at

(a) High temperature and low pressures

(b) High temperature and high pressures

(c) Low temperature and high pressures

(d) Low temperature and low pressures

Ans: (c) Low temperature and high pressures

Explanation: Boyle's law states that when a sample of gas is compressed at a constant temperature, the pressure P and volume V satisfy the equation PV = C, where C is a constant.

Q4. An ice block with a piece of lead embedded in it floats in water. If ice melts the water level

(a) Rises

(b) Falls

(c) Remains same

(d) Falls first and then rises

Ans: (b) Falls

Explanation: The water level will fall.

As a result of Archimedes' Principle, if any object is floating in a fluid, the weight of the fluid displaced by the object is equal to the weight of the object.

Now let us consider what happens when the ice melts. Ice is less dense than water. Therefore, the water displaced by floating ice is less than the volume of the ice (hence a small part of the ice sticks out of water).

Q5. The velocity of heat radiation in vacuum is

(a) Equal to that of light

(b) Less than that of light

(c) Greater than that of light

(d) Equal to that of sound

Ans: (a) Equal to that of light

Explanation: It is equal to the speed of light, or 3×10^8 m/s (approx). Thus is because heat, invacuum travels in the form of 'Infrared Radiation', a form of electromagnetic radiation.

Q6. The plastic material commonly used for making gear wheels is

(a) Polyesters

(b) Nylons

(c) Bakelite

(d) Polystyrene

Ans: (b) Nylons

Explanation: Most plastic gears are made from nylon and acetal. But nylon absorbs moisture with resultant changes in properties and dimensions.

Q7. Ultraviolet radiations of the Sun do not reach the earth because the earth’s atmosphere is surrounded by

(a) Carbon dioxide

(b) Ammonia

(c) Chlorine

(d) Ozone

Ans: (d) Ozone

Explanation: Ozone is a molecule made up of three atoms of oxygen. It works a lot like sunscreen, blocking out harmful ultraviolet (UV) rays from the sun. In recent years, the amount of ozone in the atmosphere has decreased(d)

Q8. "Curie" is a unit of

(b) Temperature

(c) Heat

(d) Energy

Explanation: The curie is a unit of ionizing radiation (radioactivity), symbolized Ci and equal to 3.7 x 10 10disintegrations or nuclear transformations per second(d) This is approximately the amount of radioactivity emitted by one gram (1 g) of radium-226. The unit is named after Pierre Curie, a French physicist.

Q9. Which of the following is used in oven ?

(a) X-rays

(b) UV rays

(c) Microwaves

Ans: (c) Microwaves

Explanation: a microwave oven uses microwaves to heat foo(d) Microwaves are a type of wave that are sandwiched between radio waves and infrared radiation on the electromagnetic spectrum. In the case of microwave ovens, the commonly used wave frequency is roughly 2,450 megahertz (2.45 gigahertz).

Q10. When heated from 0° to 10°C volume of a given mass of water will:

(c) Increase and then will decrease

(d) Decrease and then will increase

Ans: (d) Decrease and then will increase

Explanation: When water is heated from 0 0C, its volume decreases because its density increases and you can see this effect up to 4 0(c) Because the density of ice is maximum at 4 0(c) Afterwards as the density decreases the volume increases. The main reason for this is hydrogen bond in ice gets cleaved due to the melting of ice.

Q11. Energy is continuously created in the sun due to:

(a) nuclear fusion

(b) nuclear fission

Ans: (a) nuclear fusion

Explanation: The sun produces Energy by Nuclear Fusion, which is basically the fusion of two hydrogen atoms into a helium atom, when this process is done, the sun produces a huge amount of energy.

Q12. In electronics what comes under the tank circuit?

(a) Resistance and capacity

(b) Resistance and inductance

(c) Capacity and inductance

(d) Resistance, capacity and inductance

Ans: (c) Capacity and inductance

Explanation: A tank circuit is a parallel combination of a capacitor and inductor and is the most common "resonant" circuit -- a circuit that absorbs maximum power at a particular frequency (called the resonant frequency).

Q13. Coolis tube is used to produce

(b) Microwaves

(c) X-rays

(d) Gama rays

Ans: (c) X-rays

Explanation: A high voltage power source, for example 30 to 150 kilovolts (kV), called the tube voltage, is connected across cathode and anode to accelerate the electrons. The X-ray spectrum depends on the anode material and the accelerating voltage.

Q14. Which of the following is used for regulated electric supply?

(a) Zener diode

(b) Junction diode

(c) Gun diode

(d) Tunnel diode

Ans: (a) Zener diode

Explanation: Zener diodes are widely used as voltage references and as shunt regulators to regulate the voltage across small circuits. Because of the low impedance of the diode when operated like this, resistor R is used to limit the current through the circuit.

Q15. What is the orbital velocity of a geostationary satellite?

(a) 4.15 km/s

(b) 2.78 km/s

(c) 3.08 km/s

(d) 6.66 km/s

Ans: (c) 3.08 km/s

Explanation: A geostationary orbit can be achieved only at an altitude very close to 35,786 km (22,236 mi) and directly above the equator. This equates to an orbital velocity of 3.07 km/s (1.91 mi/s) and an orbital period of 1,436 minutes, which equates to almost exactly one sidereal day (23.934461223 hours).

Q16. Gamma rays can cause

(a) gene mutation

(b) sneezing

(c) burning

(d) fever

Ans: (a) gene mutation

Explanation: irradiation can cause mutations in DN(a) There are two major types of radiation: ionizing radiation and non-ionizing radiation. Ionizing radiation, such as X-rays and gamma rays, is a high-energy kind of radiation that causes ions and free radicals to form.

Q17. The substance which conducts current in the solid-state is

(a) diamond

(b) graphite

(c) iodine

(d) sodium chloride

Ans: (b) graphite

Explanation: All solid metals have some conductive properties with gold and copper being among some of the best. Some basically non-metallic materials can also conduct electricity in solid form, such as graphite and silicon. Compounds of metals do not conduct electricity as a solid, but metals are good conductors of electricity.

Q18. Which set of conditions represents the easiest way to liquefy a gas?

(a) Low temperature and high pressure

(b) High temperature and low pressure

(c) Low temperature and low pressure

(d) High temperature and high pressure

Ans: (a) Low temperature and high pressure

Explanation: gases can be liquefied by one of three general methods:

(1) By compressing the gas at temperatures less than its critical temperature;

(2) By making the gas do some kind of work against an external force, causing the gas to lose energy and change to the liquid state;

(3) By using the Joule-Thomson effect

Joule-Thomson effect, the gas is first pumped into a container under high pressure. The container is fitted with a valve with a very small opening. When the valve is opened, the gas escapes from the container and expands quickly. At the same time, its temperature drops.

Q19. What is colour of light related to?

(a) Amplitude

(b) Frequency

(c) Quality

(d) Velocity

Ans: (a) Amplitude

Explanation: colour must be connected with the frequency of light rather than the wavelength.

To check if colour changes in a denser medium. Take a laser pointer. Take a glass slab Shine laser light on the glass slab in a darkened room. Is the laser light within the slab also red as it is in the air. It is re(d) So colour is a property of frequency rather than wavelength.

Q20. What principle/law explains the working of the hydraulic brakes in automobiles?

(a) Bernoulli's law

(b) Poiseuille's principle

(c) Pascal's law

(d) Archimedes' principle

Ans: (c) Pascal's law

Explanation: Pascal's law states that when there is an increase in pressure at any point in a confined fluid, there is an equal increase at every other point in the container.

Hydraulic systems use an incompressible fluid, to transmit forces from one location to another within the fluid Most aircraft use hydraulics in the braking systems and landing gear.

Q21. The best conductor of heat among the following is

(a) alcohol

(b) mercury

(c) ether

(d) water

Ans: (b) mercury

Explanation: Like all metals, mercury is an excellent conductor of heat. This is one of the reasons why mercury is used in a traditional mercury thermometer.

Q22. What is viewed through an electron microscope?

(a) Electrons and other elementary particles

(b) Structure of bacteria and viruses

(c) Inside of human stomach

(d) Inside of the human eye

Ans: (b) Structure of bacteria and viruses

Explanation: Taking a look at viruses under the microscope. Unlike other unicellular organisms like bacteria, viruses are commonly referred to as particles rather than cells. These particles (virion) are also not alive given that they are unable to grow or multiply on their own.

Q23. What apparatus is used to locate a submerged object?

(b) Sonar

(c) Quasar

(d) Pulsar

Ans: (b) Sonar

Explanation: Sonar (originally an acronym for sound navigation 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.

Q24. The instrument which uses sound waves to measure the depth of oceans is

(b) Sonar

(c) Altimeter

(d) Venturimeter

Ans: (b) Sonar

Explanation: Sonar devices are used to measure the depth of the sea A sound is sent out and the echo monitored We know the speed of sound in water.

Q25. Which combination of colour is the most convenient during day and night time?

(a) Organe and blue

(b) White and black

(c) Yellow and blue

(d) Red and green

Ans: (d) Red and green

Explanation: Red and Green is the combination of colour which is most convenient during day and night time.