Physics - Study Mode

[#511] The electrical domestic tube light gives white fluorescent light because of
Correct Answer

(D) Falling of ultra violet rays on the white inner coating of the tube

Explanation

Solution: The electrical domestic tube light gives white fluorescent light because of falling of ultra violet rays on the white inner coating of the tube. The ultraviolet rays have high frequency and shorter wavelength are converted to visible white light with lower frequency and greater wave length.

[#512] The unit for measuring electric power is the
Correct Answer

(C) Watts

Explanation

Solution: Electricity is measured in units of power called Watts, named to honour James Watt, the inventor of the steam engine.

[#513] The device used to change the speed of an electric fan is
Correct Answer

(B) Regulator

Explanation

Solution: The device used to change the speed of an electric fan is regulator.

[#514] The material used in electric heater is
Correct Answer

(B) Nichrome

Explanation

Solution: Most heating elements use Nichrome 80/20 (80% nickel, 20% chromium) wire, ribbon, or strip. Nichrome 80/20 is an ideal material, because it has relatively high resistance and forms an adherent layer of chromium oxide when it is heated for the first time. Material beneath this layer will not oxidize, preventing the wire from breaking or burning out. Hence, Nichrome is used as heating elements.

[#515] After long periods of use, a grey spot develops on the inside of a bulb. This is because
Correct Answer

(C) Dust inside the bulb condenses on the top

Explanation

Solution: At high operating temperatures, tungsten evaporates from the filament and gradually forms a gray film on the inside of the bulb. The inert gas atoms collide with the evaporating tungsten, causing some of the tungsten atoms to return to the filament.