Hydrogen has a heat transfer co-efficient __________ times that of air?
A. 1.5
B. 2.5
C. 3.5
D. 4.5
Electrical Machine Design
Multiple inlet system of air cooling of turbo-alternators can be used for machines of rating upto_______________?
Multiple inlet system of air cooling of turbo-alternators can be used for machines of rating upto_______________?
A. 10 MW
B. 30 MW
C. 60 MW
D. 150 MW
The mcrease in heat dissipation by air blasts is due to increase in______________?
The mcrease in heat dissipation by air blasts is due to increase in______________?
A. conduction
B. convection
E. radiation
D. any ofthe above
On which of the following variables heat convected depends ?
On which of the following variables heat convected depends ?
A. Power density
B. Temperature difference between heated surface and coolant
C. Thermal resistivity, density, specific heat
D. Gravitational constant
E. All of the above
Which of the following materials is used in the manufacture of resistance grids to be used in the starters of large motors ?
Which of the following materials is used in the manufacture of resistance grids to be used in the starters of large motors ?
A. Copper
B. Aluminium
C. Steel
D. Cast-iron
The heat dissipated by from a surface depends upon its temperature and its characteristics like colour, roughness etc?
The heat dissipated by from a surface depends upon its temperature and its characteristics like colour, roughness etc?
A. conduction
B. convection
C. radiation
D. any of the above
__________is extensively used for those portions of magnetic circuit which carry steady flux and need superior mechanical properties ?
__________is extensively used for those portions of magnetic circuit which carry steady flux and need superior mechanical properties ?
A. Grey cast-iron
B. Cast steel
C. High carbon steel
D. Stainless steel
Aluminium when adopted as a conductor material in __________ transformers, decreases the overall cost of the transformer?
Aluminium when adopted as a conductor material in __________ transformers, decreases the overall cost of the transformer?
A. small size
B. medium size
C. large size
D. any of the above size
Hot rolled sheets have ___________ value of permeability?
Hot rolled sheets have ___________ value of permeability?
A. zero
B. low
C. high
D. none of the above
Materials exhibiting zero value of resistivity are known as ____________ ?
Materials exhibiting zero value of resistivity are known as ____________ ?
A. conductors
B. semiconductors
C. insulators
D. superconductors