Heating and Welding

1. Which of the following is an advantage of heating by electricity?

1. Quicker operation
2. Higher efficiency
3. Absence of flue gases
4. All of the above

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2. __________ has the highest value of thermal conductivity.

1. Copper
2. Aluminium
3. Brass
4. Steel

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3. Which of the following heating methods has maximum power factor?

1. Arc heating
2. Dielectric heating
3. Induction heating
4. Resistance heating

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4. Method has leading power factor

1. Resistance heating
2. Dielectric heating
3. Arc heating
4. Induction heating

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5. is used for heating non-conducting materials.

1. Eddy current heating
2. Arc heating
3. Induction heating
4. Dielectric heating

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6. Which of the following methods of heating is not dependent on the frequency of supply?

1. Induction heating
2. Dielectric heating
3. Electric resistance heating
4. All of the above

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7. When a body reflects entire radiation incident on it, then it is known as

1. white body
2. grey body
3. black body
4. transparent body

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8. For the transmission of heat from one body to another

1. temperature of the two bodies must be different
2. both bodies must be solids
3. both bodies must be in contact
4. at least one of the bodies must have some source of heating

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9. Heat transfer by condition will not occur when

1. bodies are kept in vacuum
2. bodies are immersed in water
3. bodies are exposed to thermal radiations
4. temperatures of the two bodies are identical

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10. A perfect black body is one that

1. transmits all incident radiations
2. absorbs all incident radiations
3. reflects all incident radiations
4. absorbs, reflects and transmits all incident radiations

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