ELECTRICAL ENGINEERING
Some important mcq
1.Luminous flux is
(a) the rate of energy radiation in the form of light waves.
(b) the part of light energy. radiated by Sun that is received on
(c)measured in lux
2. Glare is caused due to
(a) excessive luminance
(b) excessive lighting contrast in the field of vision
(c) either (a) or (b)
3. Unit of illumination is
(a) lumen
(c) lux.
(b) lambert
(d) steradians.
4. The illumination at a surface due to a source of light placed at a distance d' from the surface varies as
5.The illumination at various points on a horizontal surface illu- minated by the same source varies as
(a) cos(θ)
(b) cos(θ²)
(c) cos(θ³)
d) 1/cos(θ)
6. Carbon arc lamps are commonly used in
(a) cinema projectors.
(b) domestic lighting
(c) factory lighting
(d) street lighting
7. For two filaments of same material operating at the same tem perature, the diameter and current through filament are related by
(a) diameter directly proportional to current.
(b) diameter proportional to (current²)
(c) diameter proportional to (current)⅔
(d) none of these.
8.The melting point of tungsten is
(a) 3,400°C.
(b) 2,800°C.
(C) 2,600°C.
(d) 2,400C.
9. The vacuum inside an incandescent lamp is of the order of
(a) 10‐2 mm Hg.
(b) 10‐⁴mmHg.
(c) 10‐⁷mm Hg.
(d) 10 ‐⁸mmHg.
1o. The rate of evaporation of Upon tungsten filament in a lamp depends Upon
(a) exhaust tube diameter.
(b) glass shell diameter.
(e) vapour pressure inside.
(d) none of the above
11. Heat from the lamp filament is transmitted to the surrounding mainly through
(a) circulation
(b) conduction
(c) convection.
(d) radiation
12. Which of the following material is most commonly used for the filaments in incandscent lamps ?
(a) Tungsten
(b) Tantalum
(c) Osmium
(d) Silver
13. A zero watt lamp consumes power of
(a) zero watt.
(b) 5-10 W.
(c) about 15 W.
(d) about 25 W.
14. The safe operating temperature of a tungsten filament
(a) 1,000°C
(b) 3,000°C.
(c) 2,000°C:
(d) 3,500°C
15. The output of a tungsten filament depends on
(a) size of the shell.
(b) size of the lamp
(c) temperature of filament
(d) all of the above
16. What percentage of the input energy is radiated by filament lamps
(5) 60-70 per cent
(b) 40-50 per cent
(c) 25 - 30 per cent.
(d) 10-15 per cent.
18. An electric bulb, when broken, produces bang It is on account of
(a) vacuum inside the bulb.
(b) pressure inside is equal to that outside
(c) pressure of air in the bulb
(d) none of the above.
19. In an incandescent lamp, bird cage filament is usually used in Vacuum bulb so as to
(a) increase the life span of the filament
(b) give uniform radiations
(c) reduce the oxidation phenomenon
(d) reduce the convection loSSes.
20. Filament lamp at starting will take current
(a) equal to its full running current
(b) more than its full running current
(c) less than its full running current.
(d) none of these
21. Most affected parameter of a filament lamp due to variation in operating voltage is
(a) life.
(b) light output.
(c)luminous efficiency
(d) wattage.
22. Which gas is sometimes used in filament lamps
(a) Nitrogen.
(b) Argon
(c) Curbon dioxide.
(d) Krypton
23. Which of the following vapour/gas will give yellow colour in a filamen lamp ?
(a) Helium.
(b) Mercury.
(c) Magnesium.
(d) Sodium.
24. Magnesium vapour in a filament lamp gives
(a) green colour light.
(by pink colour light
(c) blue colour light.
(d) white colour light.
25. The gas used in a gas-filled filament lamp is
(a) helium
(b) oxygen
(c) nitrogen.
(d) ozone.
26. In filament lamps, coiled coil filaments are used in
(a) coloured lamps
(b) gas-filled lamps:
(c) low wastage lamps.
(d) higher wattage lamps.
27. In electric discharge lamps, light is produced by
(a) magnetic effect of current.
(b) heating effect of current.
(c) cathode ray emission
(d) ionisation in a gas or vapour
28. In electric discharge lamps for stabilization of are
(a) a choke is connected in series with the supply
(b) a variable resistance is connected in series with the circuit
(c) a condenser is connected across the supply
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