Electrical Engineering Materials

11. An H.R.C. fuse is

1. a ceramic body having metal and caps
2. a wire of platinum
3. a heavy cross-section of copper or aluminium
4. a ceramic tube having carbon rod inside it

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12. At transition temperature the value of critical field is

1. zero
2. negative real value
3. positive real value
4. complex value

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13. By increasing impurity content in the metal alloy the residual resistivity always

1. decreases
2. increases
3. remains constant
4. becomes temperature independent

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14. Carbon bearings are used under which of the following conditions?

1. Where lubrication is difficult or im-possible
2. Where corrosive chemical action exists
3. Where high temperature exists
4. All of the above

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15. Carbon electrodes are not used in

1. GLS lamps
2. electric arc furnace
3. dry cells
4. cinema projectors

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16. Carbon resistors are used extensively because they are

1. easy to make
2. compact
3. inexpensive
4. all of the above reasons

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17. Carbon rods are used in wet and dry cells because

1. carbon rod serves as conductor
2. carbon can resist the attack of battery acid
3. both (a) and (b)
4. either (a) or (b)

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18. Commonly used conducting materials are

1. copper
2. aluminium
3. both (a) and (b)
4. copper and silver

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19. Constantan contains

1. silver and tin
2. copper and tungsten
3. tungsten and silver
4. copper and nickel

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20. Copper, even though costly, finds use in the windings of electrical machines because

1. copper points offer low contact resistance
2. copper can be easily soldered and welded
3. copper windings are less bulky and the machines become compact
4. all of the above

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