### Physics - Thermal and Chemical Effects of Currents

#### 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
• D NONE OF THESE

#### Question - 3

Faraday's laws of electrolysis are independent of

• A temperature
• B pressure
• C nature of solvent
• D ALL OF THESE

#### 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