General Science Physics Questions
31. By how much times the orbital speed of a satellite needs to be increased to make it escape the gravitational field?
[A] √3 times
[B] 4 times
[C] 2 times
[D] √2 times
[D] √2 times
Notes:
It means that if the speed of a satellite orbiting close to the earth is made √2 times (or increased by 41%) then it will escape from the gravitational field.
32. What will be the general value of angle of contact when the liquid does not wet the solid?
[A] Acute
[B] Obtuse
[C] Zero
[D] 90°
[B] Obtuse
Notes:
When angle of contact is an obtuse angle then molecules of liquids are attracted strongly to themselves and weakly to those of solid, it costs a lot of energy to create a liquid-solid surface, and liquid then does not wet the solid. For example: water on a waxy or oily surface.
33. Which of the following waves is absorbed by the ozone layer present in the atmosphere?
[A] Gamma
[B] Visible
[C] Radio
[D] Ultra violet
[D] Ultra violet
Notes:
UV light in large quantities has harmful effects on humans. But fortunately, most of it is absorbed in the ozone layer in the atmosphere at an altitude of about 40 – 50 km.
34. What is the S.I unit of Latent heat of fusion?
[A] J kg-1 K-1
[B] J kg-2
[C] J kg K-1
[D] J kg-1
[D] J kg-1
Notes:
The latent heat for a solid liquid state change is called the latent heat of fusion The S.I. unit of the latent heat of fusion is J kg-1.
35. Which of the following principles is used to define the First law of Thermodynamics?
[A] Conservation of mass
[B] Conservation of energy
[C] Conservation of momentum
[D] Conservation of charge
[B] Conservation of energy
Notes:
The first law of thermodynamics is the general law of conservation of energy applied to any system in which energy transfer from or to the surroundings (through heat and work) is taken into account.
36. What causes the twinkling of stars?
[A] Atmospheric refraction of starlight
[B] Dispersion of starlight
[C] Scattering of starlight
[D] None
[A] Atmospheric refraction of starlight
Notes:
The twinkling of a star is due to atmospheric refraction of starlight. The starlight, on entering the earth’s atmosphere, undergoes refraction continuously before it reaches the earth.
37. Which of the following are the cases of use of concave mirrors?
[A] Search-lights
[B] Shaving mirrors
[C] Solar furnaces
[D] All of the above
[D] All of the above
Notes:
Concave mirrors are commonly used: 1. in torches, search-lights and vehicles headlights to get powerful parallel beams of light. 2. as shaving mirrors to see a larger image of the face. 3. by dentists to see large images of the teeth of patients. 4. to concentrate sunlight to produce heat in solar furnaces.
38. What of the following represents Ohm’s law (V= potential difference and I=current)?
[A] V = I 2
[B] V = 1/I
[C] V/I = constant
[D] None of the above
[C] V/I = constant
Notes:
The potential difference, V, across the ends of a given metallic wire in an electric circuit is directly proportional to the current flowing through it, provided its temperature remains the same. This is called Ohm’s law. V/I =constant.
39. What is current density?
[A] Current per unit volume
[B] Current per unit area
[C] Charge per unit area
[D] None of the above
[B] Current per unit area
Notes:
Current per unit area (taken normal to the current), I/A, is called current density and is denoted by j. The SI units of the current density are A/m2.
40. Which of the following is a limitation of Bohr’s model of atom?
- [A] it does not explain why orbits of electrons are taken as circular
- [B] it does not take into account the wave nature of electrons
- [C] Both a and b
- [D] None of the above.
[C] Both a and b
Notes:
Bohr’s model of atom does not explain why orbits of electrons are taken as circular and does not take into account the wave nature of electrons.
