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15 Thermal a - 15 THERMAL AND CHEMICAL EFFECTS OF CURRENTS Page 1 Answers at the end of all questions 1 A heater coil is cut into two equal parts

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- THERMAL AND CHEMICAL EFFECTS OF CURRENTS Page 1 ( Answers at the end of all questions ) 1 ) A heater coil is cut into two equal parts and only one part is now used in the heater. The heat generated will now be ( a ) four times ( b ) doubled ( c ) halved ( d ) one-fourth [ AIEEE 2005 ] 2 ) Two voltameters, one of copper and another of silver, are joined in parallel. When a total charge q flows through the voltameters, equal amount of metals are deposited. If the electrochemical equivalents of copper and silver are z 1 and z 2 respectively, the charge which flows through the silver voltameter is ( a ) 1 2 z z 1 q + ( b ) 2 1 z z 1 q + ( c ) 1 2 z z q ( d ) 2 1 z z q [ AIEEE 2005 ] 3 ) Time taken by a 836 W heater to heat one litre of water from 10 ° C to 40 ° C is ( a ) 50 s ( b ) 100 s ( c ) 150 s ( d ) 200 s [ AIEEE 2004 ] 4 ) The thermo-emf of a thermocouple varies with the temperature θ of the hot junction as E = a θ + b θ 2 in volts where the ratio a / b is 700 ° C. If the cold junction is kept at 0 ° C, then the neutral temperature is ( a ) 700 ° C ( b ) 350 ° C ( c ) 1400 ° C ( d ) no neutral temperature is possible for this thermocouple [ AIEEE 2004 ] 5 ) The electrochemical equivalent of metal is 3.3 × 10 - 7 kg per coulomb. The mass of the metal liberated when a three ampere current is passed for 2 seconds will be ( a ) 19.8 × 10 - 7 kg ( b ) 9.9 × 10 - 7 kg ( c ) 6.6 × 10 - 7 kg ( d ) 1.1 × 10 - 7 kg [ AIEEE 2004 ] 6 ) A 220 volt, 1000 watt bulb is connected across 110 volt mains supply. The power consumed will be ( a ) 1000 watt ( b ) 750 watt ( c ) 500 watt ( d ) 250 watt [ AIEEE 2003 ] 7 ) An electric motor operates at 20 rev / sec. What will be the approximate power delivered by the motor, if it supplies a torque of 75 N-m ? ( a ) 1550 W ( b ) 4040 W ( c ) 7730 W ( d ) 9420 W [ AIEEE 2003 ] 8 ) The negative Zn pole of a Daniell cell, sending a constant current through a circuit, decreases in mass by 0.13 g in 30 minutes. If the electrochemical equivalents of Zn and Cu are 32.5 and 31.5 respectively, then increase in the mass of positive Cu pole in this time is ( a ) 0.242 g ( b ) 0.180 g ( c ) 0.141 g ( d ) 0.126 g [ AIEEE 2003 ] 9 ) 2 litre water kept in a kettle is heated by 1 KW power source. Kettle is open and it loses heat at the rate of 160 J/s. The time taken for the temperature of kettle to change from 27 ° C to 77 ° C is ( a ) 8 min 20 sec ( b ) 6 min 20 sec ( c ) 5 min ( d ) 7 min [ IIT 2005 ] 10 ) An ideal gas enclosed in an insulated vessel is heated through a coil of resistance 100
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This note was uploaded on 11/28/2011 for the course PHYSICS 300 taught by Professor Smith during the Spring '06 term at ITT Tech Flint.

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15 Thermal a - 15 THERMAL AND CHEMICAL EFFECTS OF CURRENTS Page 1 Answers at the end of all questions 1 A heater coil is cut into two equal parts

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