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.
21. Which is the direction of magnetic field inside a magnet?
[A] from south pole to north pole
[B] from north pole to south pole
[C] from north pole till centre of the magnet
[D] None of the above
Show Answer
Correct Answer: A [from south pole to north pole]
Notes:
Inside the magnet, the direction of field lines is from its south pole to its north pole.
22. What happens to a bar magnet of dipole moment (m) is placed in a uniform magnetic field (B)?
[A] the force on the bar magnet is zero
[B] the torque on the bar magnet is m × B
[C] Both a and b
[D] None of the above
Show Answer
Correct Answer: C [Both a and b]
Notes:
When a bar magnet of dipole moment m is placed in a uniform magnetic field B: (a) the force on it is zero, (b) the torque on it is m × B, (c) its potential energy is –m.B, where we choose the zero of energy at the orientation when m is perpendicular to B.
23. Which of these rays have the highest penetrating power?
[A] Alpha
[B] Beta
[C] Gamma
[D] All have the same
Show Answer
Correct Answer: C [Gamma]
Notes:
Gamma rays have the highest penetrating power followed by Beta and the Alpha.
24. How does a semiconductor behave at absolute zero temperature?
[A] like an insulator
[B] like a conductor
[C] depends on the material
[D] None of the above
Show Answer
Correct Answer: A [like an insulator]
Notes:
At or close to absolute zero a semiconductor behaves like an insulator. When an electron gains enough energy to participate in conduction (is “free”), it is at a high energy state. When the electron is bound, and thus cannot participate in conduction, the electron is at a low energy state.
25. Convex mirror is generally used in which of the following?
[A] Rear view mirror
[B] Solar cookers
[C] Opthalmoscope
[D] Reflector for head light
Show Answer
Correct Answer: A [Rear view mirror]
Notes:
Convex mirrors are commonly used as rear-view (wing) mirrors in vehicles because they give an erect, virtual, full size diminished image of distant objects with a wider field of view.
26. When a brick is dropped in water, bubbles are seen to rise. This is due to which of the following reasons?
[A] Air in the pores of the brick
[B] Air in water
[C] Water displaced by the brick
[D] None of these
Show Answer
Correct Answer: A [Air in the pores of the brick]
Notes:
A brick is made when mud is heated and hence it remains porous. When brick is dropped in water the air which was trapped in those pores rise up and hence form the bubbles.
27. A man coming down on a lift leaves a ball from his hand. What will happen to the ball?
[A] Go up
[B] Fall down
[C] Remain stationary with respect to man
[D] Oscillate up and down
Show Answer
Correct Answer: C [Remain stationary with respect to man]
Notes:
If the man and the released ball are experiencing free fall, then the ball would be falling with same acceleration as the boy. Hence relativity says in the man’s view the ball is stationary.
28. Which of the following is the normal temperature of human body on the Kelvin scale?
[A] 280
[B] 290
[C] 300
[D] 310
Show Answer
Correct Answer: D [310]
Notes:
Normal body temperature of human is 37° C. But when we convert 37° C into Kelvin it becomes 310 K because 0° C = 0°C + 273 = 273 K.
29. Which type of wave is sound wave?
[A] Transverse wave
[B] Longitudinal wave
[C] Electromagnetic wave
[D] None of the above.
Show Answer
Correct Answer: B [Longitudinal wave]
Notes:
Sound is a longitudinal wave. Longitudinal wave is a wave where the direction of propagation of the wave and movement of particles is in the same direction where as in transverse wave they are perpendicular to each other.
Extra info: Example of transverse wave is light wave (electromagnetic wave).
30. 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.
