Physics MCQ Questions  with Answer for all Competitive Exams

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Physics MCQ Questions  with Answer

Q61. How much mechanical work must be done to completely melt 1 gram of ice at 0°C?

(a) 4.2 J

(b) 80 J

(c) 336 J

(d) 2268 J

Answer: (c)

Explanation: Work done to completely melt 1 gm of ice at 0°C

W = Q = ML

W = 1 × 336 J/gm = 336 J

Where L = (Latent heat of fusion for water)

Q62. Which once, the following is printed on a commonly used fluorescent tube light?

(a) 220K

(b) 273K

(c) 6500 K

(d) 9000 K

Answer: (c)

Explanation: A fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite mercury vapour. The excited mercury atoms produce short-wave ultraviolet light that then causes a phosphor to fluoresce, producing visible light. 6500K is usually printed on a used fluorescent tube light.

Q63. Consider the following statements:

In a nuclear reactor, a self-sustained chain reaction is possible, because:

  1. More muttons are released in each of the fission reactions.
  2. The neutrons immediately take part in the fission process.
  3. The fast neutrons are slowed down by graphite.
  4. Every neutron released in the fission reaction initiates further fission.

Which of these statements are correct?

(a) 1, 2 and 3

(b) 1 and 3

(c) 2 and 4

(d) 2, 3 and 4.

Answer: (a)

Explanation: A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. The most commonly used nuclear reactors are for the generation of electrical power and for the power in some ships. In every fission reaction in which uranium nuclei split up to give smaller nuclei three more neutrons are produced which further results in the splitting of heavy uranium nuclei and more neutrons will be produced. The statement, 1 and 2 are correct. In a nuclear reactor, all the neutrons produced cannot take pan in fission reaction, else reaction can turn out extremely violent. Thus, graphite rods are used as a control rod to slow down the speed of fast-moving neutrons. Thus, statement 3 is also correct.

Q64. Equation E = p.c. is valid for –

​(a) ​Both electron and Photon ​

(b)​ Electron only ​

(c)​ Photon only

​(d) ​Neither electron nor photon

Answer: (c)​

Explanation: The equation E = p.c. is valid for particles with zero rest mass, which is valid for photons but not for electron

Q65. A brass ball is tied to a thin wire and swung so as to move uniformly in a horizontal circle. Which of the following statements in this regard is/are true? ​

1.​ The ball moves with constant velocity ​

2.​ The ball moves with constant speed ​

3.​ The ball moves with constant acceleration

4.​ The magnitude of the acceleration of the ball is constant ​

Select the correct answer using the code given below:

​(a)​ 1 only ​

(b) ​1 and 3 ​

(c)​ 1, 2 and 4

​(d)​ 2 and 4 only

Answer: ​(d)

Explanation: ​Velocity is the vector quantity so it gets changed as the direction changes. The ball will move with constant speed and the magnitude of the acceleration of the ball will also be constant.

Q66. The final image is a simple microscope is

(a) Real, diminished, and inverted

(b) Real, magnified, and erect

(c) Virtual, magnified, and erect

(d) Virtual, diminished and erect

Answer: (c)

Explanation: Simple microscope uses a biconvex lens which forms an enlarged, erect, and virtual image of the object.

Q67. The boiling point of a liquid varies as

(a) Pressure varies

(b) Temperature varies

(c) Volume varies

(d) Density varies

Answer: (a)

Explanation: On increasing pressure, the boiling point increases. On decreasing pressure, the boiling point decreases.

Q68. Consider the following statements:

  1. A geostationary satellite is at an approximate height of 10.000 km.
  2. FM transmission of music is of very good quality because the atmospheric or man-made noises which are generally frequency variations can do little harm.

Which of the statements given above is correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer: (a)

Explanation: On increasing pressure, the boiling point increases. On decreasing pressure, the boiling point decreases.

Q69. ​Match List-I with List-II and select the correct answer with the help of codes given below:

List-IList-II
A. Temperature1. Kelvin
B. Power2. Watt
C. Pressure3. Pascal
D. Force4. Newton

Codes: A B C D

(a)        2 1 3 4

(b)       1 2 4 3

(c)        1 2 3 4

(d)       2 1 4 3

Answer: ​(c)

Explanation: ​The unit of temperature is Kelvin, power is measured in watt, pressure in Pascal, and force in newton.

Q70. A myopic eye can be corrected by using a

​(a)​ Convex lens ​

(b)​ Concave lens ​

(c)​ Cylindrical lens ​

(d) ​Plano-convex lens

Answer: (b) ​

Explanation: Near-sightedness or myopia is the inability of the eye to focus on distant objects. The near-sighted eye has no difficulty viewing nearby objects. This condition results if the light from distant objects is refracted more than is necessary. The cure for the near-sighted eye is to equip it with a diverging or concave lens. Since the nature of the problem of near-sightedness is the light before it reaches the eye. This light will then be converted by the cornea and lens to produce an image on the retina.

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