76. The earth's magnetic field always has a vertical component except at the

1. 1. magnetic equator

   
   
   

   2. magnetic poles

   
   
   

   3. geographic north pole

   
   
   

   4. latitude 45°

   
   
   

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1. View Hint View Answer Discuss in Forum

   At magnetic equator, R = H; V = 0.

   Correct Option: A

   At magnetic equator, R = H; V = 0.

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77. Parameters of electricity supply in India are

1. 1. Potential Difference of 220 V, Frequency of 50 hertz and Current Rating of 5 A / 15 A

   
   
   

   2. Potential Difference of 150 V, Frequency of 40 hertz and Current Rating of 10 A

   
   
   

   3. Potential Difference of 220 V, Frequency of 60 hertz and Current Rating of 15 A

   
   
   

   4. Potential Difference of 220 V, Frequency of 40 hertz and Current Rating of 5 A

   
   
   

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1. View Hint View Answer Discuss in Forum

   Parameters of electricity supply are different in different countries. In India they are:
   Potential Difference of 220 V, Frequency of 50 hertz and Current Rating of 5 A / 15 A.

   Correct Option: A

   Parameters of electricity supply are different in different countries. In India they are:
   Potential Difference of 220 V, Frequency of 50 hertz and Current Rating of 5 A / 15 A.

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78. Electric iron uses wires of alloy as

1. 1. they do not oxidise at high temperatures

   
   
   

   2. they do not burn at high temperatures

   
   
   

   3. both (a) and (b)

   
   
   

   4. neither (a) nor (b)

   
   
   

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1. View Hint View Answer Discuss in Forum

   both (a) and (b)

   Correct Option: C

   both (a) and (b)

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79. The frequency of A.C. mains in India is

1. 1. 30 c/s

   
   
   

   2. 50 c/s

   
   
   

   3. 60 c/s

   
   
   

   4. 120 c/s

   
   
   

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1. View Hint View Answer Discuss in Forum

   In India the frequency of A.C. current is 50 Hz.

   Correct Option: B

   In India the frequency of A.C. current is 50 Hz.

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