Physics - Study Mode
[#316] Electricity is transmitted over long distances
Correct Answer
(B) There is less wastage of energy
Explanation
Solution: The primary reason that power is transmitted at high voltages is to increase efficiency. As electricity is transmitted over long distances, there are inherent energy losses along the way.
[#317] Tungsten is used for the manufacture of the filament of an electric bulb, because
Correct Answer
(D) It has a very high melting point
Explanation
Solution: Tungsten is used in electric bulb because it has high melting point and it does not oxidize. Thus tungsten filament does not melt even when a large amount of heat is produced due to passage of current through the filament (via heating effect of current).
[#318] In a filament type light bulb most of the electric power consumed appears as
Correct Answer
(B) Infra-red rays
Explanation
Solution: In a filament type light bulb most of the electric power consumed appears as Infra-red rays. When electricity flows through the fiber, it heats up. Depending on the filament temperature, the radiation is emitted from the filament.
[#319] Which of the following metals is used for the manufacture of heating elements provided in electric iron ?
Correct Answer
(C) Nichrome
Explanation
Solution: Nichrome is the most common domestic heating element and is found in many household products. Commonly, items such as toasters, hair dryers and heaters use Nichrome coils to pass electricity and give off heat. Nichrome is made of 80 percent nickel and 20 percent chromium, and its high melting point of 1,400 degrees Celsius. Nichrome is a non-magnetic alloy of nickel, chromium, and often iron, usually used as a resistance wire. Patented in 1905, it is the oldest documented form of resistance heating alloy. A common alloy is 80% nickel and 20% chromium, by mass, but there are many others to accommodate various applications. Due to its relatively high electrical resistivity and resistance to oxidation at high temperatures, it is widely used in electric heating elements, such as in hair dryers, electric ovens, soldering iron, toasters, and even electronic cigarettes.
[#320] When an electric bulb breaks, there is an explosive sound. That is due to
Correct Answer
(C) The air outside rushing in to fill the vacuum inside the bulb
Explanation
Solution: The inside of the bulb being a vacuum, the outside air rushes in when the bulb is broken. The vibrations of the rushing air molecules produce the sound.