Physics - Thermal and Chemical Effects of Currents

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Question - 1

Important sources of e.m.f. are

A. electro-magnetic induction

B. the thermo-electric effect

C. the photo-electric effect

D. the piezo-electric effect

  • A if A and B are correctly only
  • B if A,B and C are correct only
  • C if C and D are correct only
  • D if A,B,C and D, all are correct

Question - 2

How long will it take a current of 50A to produce 32g of oxygen by the electrolysis of water? Oxygen has an atomic mass of 16 and a valence of 2.

  • A 7720 s
  • B 30880 s
  • C 15440 s

Question - 3

Faraday's laws of electrolysis are independent of

  • A temperature
  • B pressure
  • C nature of solvent

Question - 4

When 1 gram of water is formed by the combination of hydrogen and oxygen, 3800 calories of heat are evolved. Minimum voltage required to decompose 9 gram of water is

  • A 1.67 volt
  • B 2.22 voit
  • C 1.49 volt
  • D 9.00 volt

Question - 5

The heat produced in a conductor is

  • A independent of resistivity \(\rho \) of matereial of conductor
  • B proportional to \(\rho \)
  • C inversely proportional to \(\rho \)
  • D proportional to \(\sqrt { \rho } \)

Question - 6

A constant voltage is applied between the two ends of a uniform metallic wire. Some heat is developed in it. The heat developed is doubled if

  • A both length and radius of wire are halved
  • B both length and radius of wire are doubled
  • C the radius of wire is doubled
  • D the length of the wire is doubled

Question - 7

The electrochemical equivalent of a material in an electrolyte depends on

  • A the amount of material present in electrolyte
  • B the amount of charge passed through electrolyte
  • C the current through the electrolyte
  • D the nature of the material of electrolyte

Question - 8

An external resistance R is connected to a battery of e.m.f. V and internal resistance r. The Joule heat produced in resistor R is maximum when R is equal to

  • A r
  • B r/2
  • C 2r
  • D infinitely large

Question - 9

Gases begin to conduct electricity at low pressure because

  • A gases turn to plasma
  • B mean free path increases
  • C temperature decreases
  • D electrons in atoms can move freely at low pressure

Question - 10

The commercial aluminium (trivalent atomic weight = 27) is generally obtained by electrolysis. The total charge required to deposit 9 gram of aluminium is

  • A 3266.6 coulomb
  • B 96500 coulomb
  • C 6.024 X 1023 coulomb
  • D 65900 coulomb