HCS MCQ Series: Physics-I

Physics Multiple Choice Questions For HCS Exam

Haryana Civil Services Exam 2020

Important 20000 MCQ Series For HCS Exam: PHYSICS PART-I

Q1. Which electromagnetic radiation is used for satellite communication?

(a) Ultraviolet

(b) Infrared

(c) Microwave

(d) Millimeter wave

Ans: (c) Microwave

Explanation: Microwave is a line-of-sight wireless communication technology that uses high-frequency beams of radio waves to provide high-speed wireless connections that can send and receive voice, video, and data information.

Q2. Solar cells work on the principle of

(a) Photovoltaic effect 

(b) photoelectric effect 

(c) photoconductive effect

(d) photosynthesis

Ans: (a) Photovoltaic effect

Explanation: The photovoltaic effect is the creation of voltage and electric current in a material upon exposure to light and is a physical and chemical phenomenon. The photovoltaic effect is closely related to the photoelectric effect.

Q3. Materials for rain-proof coats and tents owe their water proof properties to

(a) Surface tension

(b) Viscosity

(c) Specific gravity

(d) Elasticity

Ans: (a)  Surface tension

Explanation: Materials used to make raincoats have high surface tension because due to surface tension water droplets do not stick to the material. Surface tension is the tendency of fluid surfaces to shrink into the minimum surface area possible. Surface tension allows insects (e.g. water striders), usually denser than water, to float and slide on a water surface.

Q4. X-rays region lies between 

(a) Ultraviolet and visible region

(b) Visible and infrared region

(c) Gamma-rays and ultraviolet region

(d) Short radio waves and long radio waves

Ans: (c) Gamma-rays and ultraviolet region

Explanation: Soft X-rays have relatively short wavelengths of about 10 nanometers (a nanometer is one-billionth of a meter), and so they fall in the range of the electromagnetic (EM) spectrum between ultraviolet (UV) light and gamma-rays. ... These electromagnetic waves occupy the same region of the EM spectrum as gamma-rays.

Q5. A star appears twinkling in the sky because of

(a) scattering of light by atmosphere

(b) reflection of light by atmosphere

(c) refraction of light by atmosphere

(d) diffraction of light by atmosphere

Ans: (c) refraction of light by atmosphere

Explanation: Stars do not really twinkle, they just appear to twinkle when seen from the surface of Earth. The stars twinkle in the night sky because of the effects of our atmosphere. When starlight enters our atmosphere it is affected by winds in the atmosphere and by areas with different temperatures and densities.

Q6. When two ice cubes are pressed together, they join to form one cube. Which one of the following helps to hold them together?

(a) Hydrogen bond formation

(b) Vander walls forces   

(c) Covalent attraction

(d) Dipole interaction

Ans: (a) Hydrogen bond formation

Explanation: When the two ice cubes are pressed together, melting point of ice is lowered, so they melt to form a thin layer of water (between them). On releasing the pressure, the water formed freezes because decrease in pressure raises the freezing point. Hence the two cubes stick together, this is because of hydrogen bond formation.

Q7. Microphone is a device which transforms the

(a) sound signal into current signal

(b) current signal into sound signal

(c) sound signal into light signal

(d) light signal into sound signal

Ans: (a) sound signal into current signal

Explanation: Microphones are a type of transducer - a device which converts energy from one form to another. Microphones convert acoustical energy (sound waves) into electrical energy (the audio signal).

Q8. Pressure Cooker cooks faster because

(a) boiling point decreases with rise of pressure

(b) it cooks the food at low pressure

(c) higher temperature is attained for cooking

(d) the material of the cooker is a good conductor

Ans: (c) higher temperature is attained for cooking

Explanation: This compression increases the pressure inside the cooker to more than atmospheric pressure which in turns increases the boiling point of the remaining water. ... Higher temperature of water means higher transfer of heat to food kept in it and hence the faster cooking.

Q9. When a strong beam of light is passed through a colloidal solution, the light will

(a) be scattered

(b) pass unchanged

(c) be absorbed

(d) be reflected

Ans: (a) be scattered

Explanation:

When a beam of light is passed through a colloidal solution, then scattering of light is observed. This is known as the Tyndall effect. This scattering of light illuminates the path of the beam in the colloidal solution.

Q10. If the diameter of a capillary is doubled, then the rise of water in it will be

(a) two times

(b) half

(c) four times

(d) no change

Ans: (b) half

Explanation:

The height of the liquid column in a capillary tube is inversely proportional to its radius as given by the formula

h=2Tcosø/pgr (where, T=surface tension, p=density, r= radius of capillary tube)

So if the radius of the capillary tube is doubled, the height of the liquid column inside it is reduced by two times.

Q11. Why the needle of iron swims on water surface when it is kept gently?

(a) It will remain under the water when it will displace more water than its weight

(b) the density of needle is less than that of water

(c) due to surface tension

(d) due to its shape

Ans: (c) due to surface tension

Explanation:

This is due to surface tension. A phenomenon found at the edge of fluid The surface is held under tension because the surface molecules of the water are more attracted to the main body of the water than they are to the air. This is the same phenomenon that causes water to seek the smallest surface area, resulting in small amounts of water beading and forming droplets.

Q12. The mass of a star is two times the mass of the Sun.  How it will come to an end?

(a) Neutron Star

(b) Black hole

(c) White Dwarf

(d) Red Giant

Ans: (a) Neutron Star 

Explanation: If the star's remaining mass is between 1 1/2 to 3 times the mass of the Sun, it will collapse into a small, dense neutron star (about ten miles in diameter, about 1.4 times the mass of the Sun, with an extraordinarily strong magnetic field, and rapid spin).

Q13. Raindrops fall from a great height. Which among the following statements is true regarding it?

(a) they fall with that ultimate velocity, which are different for different droplets.

(b) they fall with same ultimate velocity.

(c) their velocity increases and they fall with different velocity on the earth

(d) their velocity increases and they fall with same velocity on the earth

Ans: (a) they fall with that ultimate velocity, which are different for different droplets

Q14. On which of the following techniques photo state machine works?

(a) Magnetic Image-Making 

(b) Thermal Image— Making

(c) Electrostatic Image— Making  

(d) Electromagnetic Image - Making

Ans: (c) Electrostatic Image— Making

Explanation: A photocopier is a machine that makes copies of documents and other visual images onto paper or plastic film quickly and cheaply. Most modern photocopiers use a technology called xerography, a dry process that uses electrostatic charges on a light-sensitive photoreceptor.

Q15. One Kilowatt hour is equal to-

(a) 3.6 Megajoule

(b) 3.8 Mega Joule

(c) 3.2 Mega Joule

(d) 4.0 Mega Joule

Ans: (a) 3.6 Megajoule

Explanation: One watt is equal to 1 J/s. One kilowatt-hour is 3.6 megajoules, which is the amount of energy converted if work is done at an average rate of one thousand watts for one hour.

Q16. What is the minimum escape velocity of rocket to be launched into space?

(a) 5 Km/Sec

(b) 6 Km/Sec

(c) 11 Km/Sec

(d) 15 Km/Sec

Ans: (c) 11 Km/Sec

Explanation: The escape velocity from Earth is about 11.186 km/s (6.951 mi/s; 40,270 km/h; 36,700 ft/s; 25,020 mph; 21,744 kn) at the surface.

Q17. Which of the following statements is true when we see ’rainbow’?

(a) We face sun and raindrops

(b) The Sun remains behind us and we face raindrops

(c) In light rainfall, we face Sun

(d) The sky remains clear and the sun is at lower position in the sky

Ans: (b) The Sun remains behind us and we face raindrops

Explanation: The sun always has to be behind you, though, because the light gets refracted back in the general direction it came from. You'll never see a rainbow when you're facing the sun. From wherever you're standing, it looks like the rainbow actually exists in some physical form.

Q18. How much calorie of energy is released by a boiled egg?

(a) 40

(b) 50

(c) 60

(d) 77

Ans: (d) 77

Explanation: One large hard-boiled egg contains 77 calories. Eating one hard-boiled egg provides 4 percent of your daily caloric needs based on a 2,000-calorie diet.

Q19. The splitting of different colours of light in a prism is

(a) Reflection of light

(b) Dispersion of light

(c) Diffraction of light

(d) Refraction of light

Ans: (b) Dispersion of light

Explanation: These colors are often observed as light passes through a triangular prism. Upon passage through the prism, the white light is separated into its component colors - red, orange, yellow, green, blue, and violet. The separation of visible light into its different colors is known as dispersion.

Q20. A boat will submerge when it displaces water equal to its own: 

(a) volume

(b) weight

(c) surface area  

(d) density

Ans: (b) weight

Explanation: A boat will float when the weight of water it displaces equal the weight of the boat and anything will float if it is shaped to displace its own weight

Q21. Surface tension in a liquid is due to:

(a) Adhesive force between molecules

(b) Cohesive force between molecules

(c) Gravitational force between molecules

(d) Electrical force between molecules.

Ans: (b) Cohesive force between molecules

Explanation: Cohesive forces are the intermolecular forces (such as those from hydrogen bonding and Van der Waals forces) which cause a tendency in liquids to resist separation. These attractive forces exist between molecules of the same substance.

Q22. A circular plate, a cube, and a sphere, all made up of same material and having the same mass, are heated to 300°C and left in a room. Which of them will have the slowest rate of cooling?

(a) Circular plate

(b) Cube

(c) Sphere

(d) All will cool at the same rate 

Ans: (c) Sphere

Explanation: The circular plate will cool fastest and the sphere will cool the slowest. The rate of heat transfer is directly proportional to the surface area.

Q23. Optic fibres are used in: 

(a) CAT scans

(b) X-ray photos

(c) Ultrasound scans

(d) Endoscopy

Ans: (d) Endoscopy

Explanation: Endoscopes use optical fibres to produce an image of inside the body. A doctor can insert a bundle of optical fibres into the body. Some carrylight into the body and some carry light reflected off internal body surfaces back out.

Q24. Two waves, each of amplitude 1.5 mm and frequency 10 Hz, are traveling in the opposite direction with a speed of 20 mm/s. The distance in mm between adjacent nodes is:

(a) 1.0  

(b) 1.2

(c) 1.5  

(d) 2.0

Ans: (d) 2.0

Explanation:

The distance between two adjacent nodes will be 2 mm

Given data,

Amplitude = 1.5 mm

Frequency = 10 hz

speed = 20 mm/sec

Distance between two adjacent nodes is nothing but the wavelength of the wave.

we know that,

wavelength x frequency = speed

=> wavelength x 10 = 20

=> wavelength = 2 mm

Hence the distance between two adjacent nodes will be 2 mm.

Q25. The snow on the mountains does NOT melt all at once when it is heated by the sun because:

(a) it becomes very hard

(b) it reflects most of the heat from the sun

(c) it has a low specific heat capacity

(d) it has a high latent heat of fusion 

Ans: (b) it reflects most of the heat from the sun

Explanation: Newly formed snow reflects about 90 percent of the sunlight that falls upon it. This means that the sun is powerless to melt clean snow. And when snow does melt, it is not because of the sunlight. Snow does not melt on a spring day because of the sun’s heat. It melts because of the warm air from the sea.

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