Physics MCQs
Physics Objective (Multiple Choice) General Knowledge & General Science Questions & Answers for SSC-CGL, UPPSC, NDA, CDS and all one day examinations of India.
31. Atmospheric pressure exerted on earth is due to the which of the following reasons?
[A] Rotation of earth
[B] Revolution of earth
[C] Gravitational pull
[D] Uneven heating of earth
Show Answer
Correct Answer: C [Gravitational pull]
Notes:
The atmospheric pressure at the surface of the Earth is due to gravitational pull of the earth and is about 14.7 psi. That means that the weight of a column of air which has a cross section of 1 square inch and which stretches from the surface of the Earth to space is 14.7 pounds.
32. A passing motorcycle causes distortion or disturbance with reception of signal in radio and T.V. Which of the following is the cause of this?
[A] The intense sound waves effect the small electronic devices of the receptor
[B] The vehicle’s metal parts block/distort the radio waves
[C] The spark plug fitted in the engine produces electro-magnetic signals due to sparking
[D] Modern motor-cycles are fitted with electric ignition system which produces radio waves
Show Answer
Correct Answer: C [The spark plug fitted in the engine produces electro-magnetic signals due to sparking]
Notes:
A passing motorcycle causes distortion or disturbance with reception of signal in radio and T.V. The cause of this is the spark plug fitted in the engine produces electro-magnetic signals due to sparking.
33. Domestic electrical wiring refers basically to which of the following connections?
[A] Series connection
[B] parallel connection
[C] combination of series and parallel connections
[D] series connection within each room and parallel connection elsewhere
Show Answer
Correct Answer: B [parallel connection]
Notes:
Domestic electrical wiring is basically a parallel combination because when appliances are connected in a parallel attach men each of them can be put on or off independently.
34. Which among the following has highest energy in the Electromagnetic spectrum?
[A] X rays
[B] Ultraviolet rays
[C] Micro waves
[D] Gamma rays
Show Answer
Correct Answer: D [Gamma rays]
Notes:
Gamma rays of Electromagnetic spectrum has highest energy.
Descending order of energies of different portions of the spectrum: Gamma rays > X rays > Ultraviolet rays > Visible spectrum > Infrared rays > Micro waves > Radio waves.
Extra info: Wavelengths of the above portions of the spectrum is inverse to the energies. eg: Gamma wave has shortest wavelength and radio waves have highest wavelength.
35. What is the charge of X rays?
[A] Positive
[B] Negative
[C] No charge
[D] Charge varies
Show Answer
Correct Answer: C [No charge]
Notes:
X rays are part of electromagnetic spectrum which does not contain any charge i.e. it is neutral.
36. According to the Kepler’s law of planetary motion, square of the time period is proportional to__?
[A] semi-major axis
[B] square of the semi-major axis
[C] cube of the semi-major axis
[D] fourth power of the semi-major axis
Show Answer
Correct Answer: C [cube of the semi-major axis]
Notes:
Kepler’s third law of planetary motion states that the square of the time period is proportional to the cube of the semi-major axis. The Ist law states that all planets revolve around the sun in the eliptical orbit while the second law states that all planets sweep equal area, in equal interval of time.
37. Which of the following is a scalar quantity ?
[A] Velocity
[B] Force
[C] Angular momentum
[D] Electrostatic potential
Show Answer
Correct Answer: D [Electrostatic potential]
Notes:
The electrostatic potential at any point in an electric field is defined as the work done in bringing a unit positive charge from infinity to that point against the electric force of the field. It is given by, V = W/q, where V is the potential, W is work done, and q the charge. Because work and charge both are scalar quantity, electrostatic potential is also a scalar quantity.
38. The apparent weight of a man in a lift is less than the real weight when__:
[A] the lift is going up with an acceleration
[B] the lift is going down with uniform speed
[C] the lift is going up with uniform speed
[D] the lift is going down with an acceleration
Show Answer
Correct Answer: D [the lift is going down with an acceleration]
Notes:
If the lift accelerates downwards with acceleration a, then the apparent weight of the man standing in the lift will be less than the true weight of the man by an amount ma. On the contrary, if the lift accelerates upwards, then the apparent weight of the man will be greater than his true weight. The difference in real and apparent weight is simply because of increasing or decreasing distance froms canth surface.
39. Which of the following quantity is a measure of inertia ?
[A] Velocity
[B] Acceleration
[C] Mass
[D] Weight
Show Answer
Correct Answer: C [Mass]
Notes:
Inertia is defined as resistance of any object to any change of state of motion. The tendency of an object to resist changes in its state of motion varies with mass. Mass of an object is the measure of inertia of that object. The more inertia that an object has, the more mass that it has. A more massive object has a greater tendency to resist changes in its state of motion.
40. Law of Inertia is also known as _________.
[A] Newton’s fist law of motion
[B] Newton’s second law of motion
[C] Newton’s third law of motion
[D] None of these
Show Answer
Correct Answer: A [Newton’s fist law of motion]
Notes:
According to Newton’s First Law of Motion, an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. This is also known as Law of Inertia.
