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# Physics MCQ Questions  with Answer for all Competitive Exams

#### Physics MCQ Questions  with Answer

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Q26. A coil and a bulb are connected in series with a 5V DC source. When a soft iron core is inserted in the coil, the light emerging from the bulb –

​(a)​ Increases ​

(b) ​Decreases ​

(c)​ Remains the same ​

(d)​ Become off

 Answer: (c)​Explanation: The resistance offered by the coil due to DC current remains zero hence there be no effect on light emerging from the bulb

Q27. Consider the following statements:

A 4-wheel vehicle moving in a sharp circular path at high speed will:

1. Overturn about its outer wheels
2. Overturn about its inner wheels
3. Skid outwards
4. Skid Inwards

Which of these statements are correct?

(a) I and 3

(b) 2 and 4

(c) 2and 3

(d) 1 and 4

 Answer: (a)Explanation: In the case of an object moving along a circular path two types of forces centripetal and centrifugal act upon it. As they have the opposite impacts thus, the object remains in balance. When centrifugal force gets disturbed then the object will leave the balance and skid toward an outward direction.

Q28. A person standing on a railway platform listens to the whistles of arriving and departing trains.

(a) The same in both cases in all respects

(b) Of higher intensity when the train arrives

(c) Of higher pitch when the train arrives

(d) Of higher pitch when the train departs

 Answer: (c)Explanation: The sound of the higher pitch will be heard compared to the sound of lower pitch.

Q29. ​If the doors of a refrigerator are left open for a few hours, the room temperature will ​

(a)​ Decrease ​

(b) ​Increase ​

(c) ​Remain the same ​

(d)​ Decrease only in the area in the vicinity of the refrigerator

 Answer: ​(b)Explanation: ​If the doors of a refrigerator are left open for a few hours, the room temperature will increase as heat is merely recycled from the room into the refrigerator and then back into the room. Thus, net room temperature would increase from the heat of the motor that would be constantly running to move energy around in a circle.

Q30. An electron and a proton are located in a uniform electric field. They will experience – ​

(a) ​Equal forces in the same direction ​

(b) ​Forces equal in magnitude ​

(c)​ Equal acceleration in opposite directions ​

(d)​ Acceleration equal in magnitude

 Answer: (b)​Explanation: The electron and proton carry opposite charges but are equal in magnitude hence the forces acting on these particles in a uniform electric field will be equal in magnitude but in opposite direction. Electron and proton differ in mass hence the acceleration will be different in these two particles.

Q31. A car is running on a road at a uniform speed of 60 km/h. The net resultant force on the car is:

(a) Driving force in the direction of car’s motion

(b) Resistance force opposite to the direction of car’s motion

(c) An inclined force

(d) Equal to zero

 Answer: (d)Explanation: By Newton’s second law F = ma. If a = 0, Fnet =0 Thus, the resultant force is zero.

Q32. What is the SI unit of Torque?

(a) Newton/meter

(b) Newton meter

(c) Newton second

(d) Newton/meter squared

 Answer: (b)Explanation: Torque = Force × perpendicular distance.SI unit of Torque will be = Newton meter

Q33. The transformer is used for –

(a) To increase the A.C. voltage

(b) To increase DC. Voltage

(c) To convert Electric Energy into heat energy

(d) To convert AC into DC.

 Answer: (a)Explanation: A transformer is a device that is used to increase or decrease the alternating current voltage.

Q34. Einstein got a noble prize for ​

(a)​ Photoelectric effect​ ​

(b) ​Compton effect ​

(c)​ Theory of relativity​

​(d)​ None of these

 Answer: (a)Explanation: ​When light shines on a metal electrons can be ejected from the surface of the metal in the phenomenon known as the photoelectric effect. Einstein received a noble prize for the discovery of the same. ​​While, Compton effect, discovered by Arthur Holly Compton, is the inelastic scattering of a photon by a charged particle, usually an electron. It results in a decrease in energy of the photon called the Compton Effect. ​​The theory of relativity determined that the laws of physics are the same for all non-accelerating observers.

Q35. What type of electromagnetic radiation is used in the remote control of a television? ​

(a) ​Infrared

​(b)​ Ultraviolet ​

(c)​ Visible ​

(d)​ None of these

 Answer: (a)Explanation: ​Infrared is used in the remote control of a television. It has a wavelength greater than visible light (> 800nm) which is invisible to the human eye but can be felt as heat.

Q36. An air bubble in water will act like a:

(a) Convex mirror

(b) Convex lens

(c) Concave mirror

(d) Concave lens

 Answer: (d)Explanation: Air bubbles in water would act as a diverging lens because the Index of refraction of air is less than that of water.

Q37. Who discovered colour photography?

(a) Robert Noyce

(b) Enrico Fermi

(c) John Logie Baird

(d) James Clerk Maxwell

 Answer: (d)Explanation: Colour photography was discovered by James Clerk Maxwell in 1855. The first demonstration of colour photography by three colour methods was suggested by him in 1855.

Q38. What is myopia?

(a) Inability to see distant objects clearly

(b) Abnormal functioning of the thyroid gland

(c) It is a condition of enlargement of the heart

(d) It is a kidney disorder

 Answer: (a)Explanation: Myopia is also known as Short-sightedness in which a person can see near objects clearly but cannot see distant objects distinctly.

Q39. The colour of light is determined by its

​(a)​ Amplitude ​

(b)​ Wavelength ​

(c) ​Intensity ​

(d)​ Velocity

 Answer: (b)Explanation: ​Light is made up of wavelengths of light, and each wavelength designates a particular colour. The colour of an object is the wavelengths of light that it reflects and the colour we see is a result of which wavelengths are reflected back to our eyes.

Q40. ​If the motion of an object is represented by a straight line parallel to the time axis in a distance-time graph, then the object undergoes​​​

(a)​ An acceleration motion ​

(b)​ A decelerated motion ​

(c)​ A uniform non-zero velocity motion ​

(d) ​A zero velocity motion

 Answer: ​(d)​Explanation: The distance-time graph parallels the time axis. ​​It is clear from the graph that the position of the object is not changing with the change in time, hence the object is at rest, or in other words, we can say that it is a zero velocity motion.

Q41. Total internal reflection can take place when light travels from:

(a) Diamond to glass

(b) Water to glass

(c) Air to water

(d) Air to glass

 Answer: (a)Explanation: Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal surface. If the refractive index is lower on the other side of the boundary, no light can pass through and all light is reflected. The critical angle is the angle of incidence above which the total internal reflection occurs. Total internal reflection takes place when light travels from an optically denser medium to an optically rarer medium. The Refractive index of diamond is very high (2,417) whereas the refractive index of glass is only in between (1.5 to 1.6), whereas in the rest all options there is no possibility of total internal reflection because of the refractive index of water (1.33) and air (1.0005) islets than the refractive index of glass.

Q42. The Sky appears to an astronaut–

(a) White

(b) Bark Blue

(c) Light Green

(d) Black

 Answer: (d)Explanation: As in outer space there is no atmosphere to scatter light. So the sky appears black to an astronaut.

Q43. A blackbody can absorb radiations of

(a) Lower wavelengths only

(b) Intermediate wavelength only

(c) Higher wavelengths only

(d) All wavelengths

 Answer: (d)Explanation: A blackbody is a body that absorbs all incident radiations falling on it regardless of the frequency and wavelength of the radiation.

Q44. What happens when a heavy object and a light object are allowed to fall from a certain height in the absence of air? ​

(a)​ Heavy object reaches the ground later than the lighter object​ ​

(b) ​Lighter object reaches the ground later than the heavier object ​

(c) ​Both heavy and light objects reach the ground simultaneously​ ​

(d) ​None of these

 Answer: ​(c)Explanation: ​If no air resistance is present, the rate of descent depends only on how far the object has fallen, no matter how heavy the object is. This means that two objects will reach the ground at the same time if they are dropped simultaneously from the same height. This statement follows the law of conservation of energy. However, if air resistance is present, then the shape of the object becomes important.

Q45. Consider the following statements and select the correct code. ​

Assertion (A): A stick is dipped in water in a slanting position. If observed sideways, the stick appears short and bent at the surface of the water. ​

Reason (R): The light coming from the stick undergoes scattering from water molecules giving the stick a short and bent appearance. ​

Codes: ​

(a)​ Both A and R are true and R is the correct explanation of A. ​

(b)​ Both A and R are true, but R is not the correct explanation of A. ​

(c)​ A is true, but R is false. ​

(d)​ A is false, but R is true.

 Answer: (c)​Explanation: When a stick is dipped in water, the ray of light that travels from the stick to the observer travels from a denser medium to a rarer medium and bends away from the normal. Thus, every point of the dipped stick produces a vertical image that is slightly above the original position. Thus, the stick appears to be slightly bent and shorter.

Q46. In a refrigerator, a cooling system should always be

(a) At the top

(b) At the bottom

(c) At the middle

(d) Can be anywhere

 Answer: (a)Explanation: Air on getting warmer rises up. This air is trapped by the cooling unit on the upward side and made cool.

Q47. The owl can see most clearly in total darkness because

(a) It has squint eyes

(b) It has large eyes with rods directed forward, giving it binocular sight

(c) It has light bulbs in its eyes provided by nature

(d) It produces infrasonic sounds

 Answer: (b)Explanation: Owls have more rods (which help to see at night) in their eyes and they have large eyes that make it lighter to enter the eyes.

Q48. A noise level of 100 decibels would correspond to:

(a) Just audible sound

(b) Ordinary conversation

(c) Sound from a noisy street

(d) Noise from a machine shop

 Answer: (d)Explanation: The decibel is widely known as a measure of sound pressure level but is also used for a wide variety of other measurements in science and engineering. The decibel is commonly used in acoustics to quantify sound levels relative to a 0 dB reference which has Men defined as a sound pressure level of 0.0002 microbars. The noise level of 100 decibels would correspond to noise from a machine shop.

Q49. ​In fibre-optics, the signal source is –​

​(a)​ Lightwaves ​

(b)​ Sound waves

​(c) ​a-rays

​(d)​ Cosmic rays

 Answer: (a) ​Explanation: Fibre optics is the science of transmitting data, voice, and images by the passage of light through thin, transparent fibres.

Q50. Which one among the following happens when a swing rises to a certain height from its rest position?

​(a) ​Its potential energy decreases while kinetic energy increases ​

(b) ​Its kinetic energy decreases while potential energy increases ​

(c)​ Both potential and kinetic energy decrease ​

(d)​ Both potential and kinetic energy increase

 Answer: (b)​Explanation: As the swing rises, its kinetic energy changes to potential energy; as with height potential energy P.E. = mgh increases. And according to the law of conservation of energy total energy E = K.E + P. E constant.

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