Physcis-scientific-assistance

  1. A pin hole box is the example of ideal black body.
  2. Light year is the unit of distance.
  3. Permanent magnet can be made from cobalt.
  4. Compton effect is associated with x-rays. Compton effect, increase in wavelength of X-rays and other enegetic electromagnetic radiationd that have been elastically scattered by electrons. It is a principle way in which radiant energy is absorbed in matter.
  5. The forward voltage drop acriss a silicon diode is about 0.7V.
  6. The leakage current in a crystal diode is due to a minority carriers.
  7. It the doping level of crystal diode is increased, the breakdown voltage is decreased.
  8. When tge graph between current through and voltage across a device is a straight line, the device is referred to as linear.
  9. A zener diode has one pn junction. It is used as a voltage regulator.
  10. Bats detect the obstacles in their path by receiving the reflected ultrasonic waves.
  11. The minimum distance between the source and the reflector, so that an echo is heard is approximately equal to 17m.
  12. When sound travels through air, the air particles viberate along the direction of wave prooagation.
  13. Frequency will remain unchanged when a sound wave travel in air or in water.
  14. Vinrations inside the ear are amplified by the three bones namely the hammer, anvil and stirrup in the middle ear.
  15. When the angle of contact between a solid and a liquid is 90 degree, then Cohesive force = Adhesive force.
  16. The rise of a liquid in a capillary tube does not depend upon Atmospheric pressure. But do depend upon angle of contact, density of the liquid and radius of the capillary tube.
  17. The pressure just below the meniscus of water is less than just above it.
  18. Meniscus of mercury in capillary is (PMT MP 88) convex.
  19. A freely suspended magnet will always come to rest in the direction North-South.
  20. Magnetic flux  is a scalar quantity.
  21. The specific resistance of a wire dependa on the material of the wire. At a fixed temperature amount ofresistance offered in the flow of current by a conductor having unit length and unit cross section is called its specific resistance. The unit ofspecific resistance is ohm-meter (Ω-m). Specific resistivity of conductor depends on the material of the conductor and its temperature.
  22. The resiatance of a conductor is due to the collision of electrons with atoms.
  23. Sun appears red at sun rise and sunset due to scattering of shorter wavelengths.
  24. Tyndall effect is tge scattering of the light by colloidal particles.
  25. If two bodies of different masses, initially at rest, are acted upon by the same force for the same time, then both bodies acquire the same momentum.
  26. Large transformers, when used for some time, become very hot and are cooled by circulating oil. The heating of the transfirmer is due ti both the heating effect of current and hysteresis loss. The energy lost as heat, which is known as the hysteresis loss, in reversing the magnetization of the material is proportional to the area of the hysteresis loop. Therefore, cores of transformers are made of materials with narrow hysteresis loops so that little energy will be wasted in the form of heat.
  27.  Rectifiers are used to convert Ac into DC.
  28. Sound waves in air are longitudnal.
  29. When a bar magnet is suspended in a uniform magnetic field, the bar magnet will turn in the field.
  30. A bar magnet kept in a magnetic field becomes parallel to the field.
  31. Ampere-meter2 is the unit of mag etic field intensity. Magnetic moment is a torque on a bar magnet.
  32. When a glass is introduced in between the plates of a parallel plate air condenser, its capacitance will increase.
  33. If a negatively charged conductor is brought near a positively charged conductor, its potential decreases.
  34. The capacitance of a capacitor when the diatance between the two plates is doubled is halved.
  35. Logical algebra was developed by George Boole
  36. The gate which is called an invertor is NOT gate.
  37. The light which cannot be completely place polarised by reflection is white color.
  38. The gate which is called the universal gate is NOR gate.
  39. An electronic oscillator is device which produces carrier waves.
  40. The range of the projectile depends on the square of the initial velocity and sine of twice the projection angle theta. Sin2theta
  41. Fathometer is used to measure depth of ocean.
  42. Convection is the process of heat transfer from one location to the next by the movement of fluids.
  43. Concept of india was developed by the Galileo.
  44. The motion on a curved path, when one component of velocity is constant and the other os variable is called Projectile motion.
  45. The angle between centripetal acceleration and tangential acceleration is 90 degree.
  46. Large angle produces high trajectory.
  47. Micro waves is used for communication by artificial satellites.
  48. The rate of transfer of charges through a circuit is called current.
  49. The power dissipated in a resistance is given by I^2*R; IV and V^2/R.
  50. When a p.d. is applied across conductor, the electrons experience a force in the direction opposite to the established electric field.
  51. All electrical appliances are connected in parallel to each other between the main line and the neutral wire to get different current and the same potential difference.
  52. In a thermocouple heart energy is converted into electrical energy.
  53. Ohm is equal V/A
  54. The number of coloumbs of charges that passes any section of the conductors in one second is called current.
  55. The treminal potential difference of a battery is equal to is emf when it’s internal resistance is zero.
  56. TIR will occur if the angle of refraction is 90 degree.
  57. The image formed by a plane mirror is laterally inverted.
  58. Absolute effective index of any medium is always >1.
  59. No matter how far is the object from the mirror, the image of the object appears errect. The mirror is convex mirror.
  60. For a plane mirror, magnification (m) = 1.
  61. Heat produce in a resiator = I^2*R*T
  62. Ohms law is not obeyed by both electrolytes and semiconductor.
  63. What is the effect of changing thw wire 8n a circuit from a straoght thick wire to a longer (coiled) thick wire? The bulb stay at the same level of brightness.
  64. Standard resistor is made up of constantan.
  65. Magnin is an alloy of: manganese, copper and nickel.
  66. The SI unit of electrical conductance is Siemens.
  67. One decay per second is equal to one bequerel.
  68. 1 torr = 133 pascal
  69. The collector side of transistor is moderately doped and larger.
  70. The second law (clausius statement) of thermodynamics states that, no process is possible whose sole result is the transfer of heat from a colder object to a hotter object.

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