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18. Explain the following.
(a)
Why is the tungsten used almost exclusively for filament of electric lamps?
(b) Why are the conductors of electric heating devices, such as bread-toasters
and electric irons, made of an alloy rather than a pure metal?
(c) Why is the series arrangement not used for domestic circuits?
(d) How does the resistance of a wire vary with its area of cross-section?
Why are copper and aluminium wires usually employed for electricity
transmission?
rel
Answers
Answer:
Tungsten metal is used exclusively for making the filament of electric bulbs because it has a very high melting point. Due to its high melting point, the tungsten filament can be kept white hot without melting away.
The conductors of electric heating devices such as bread toasters and electric irons are made of alloy because resistivity of an alloy is more than that of metals which produces large amount of heat. ... So they are usually used for electricity transmission.
A series arrangement is not used for connecting domestic electrical appliances in a circuit because if one electrical appliance stops working due to some defect, then all other appliance also stop working as the whole circuit is broken.
(d) Resistance (R) of a wire is inversely proportional to its area of cross-section (A), i.e. when area of cross section increases the resistance decreases or vice versa. (e) Copper and aluminium are good conductors of electricity also they have low resistivity. So they are usually used for electricity transmission.
Answer 1
Tungsten metal is used exclusively for making the filament of electric bulbs because it has a very high melting point. Due to its high melting point, the tungsten filament can be kept white hot without melting away.
Answer 2
The conductors of electric heating devices such as bread toasters and electric irons are made of alloy because resistivity of an alloy is more than that of metals which produces large amount of heat. ... So they are usually used for electricity transmission.
Answer 3
A series arrangement is not used for connecting domestic electrical appliances in a circuit because if one electrical appliance stops working due to some defect, then all other appliance also stop working as the whole circuit is broken.
Answer 4
(d) Resistance (R) of a wire is inversely proportional to its area of cross-section (A), i.e. when area of cross section increases the resistance decreases or vice versa. (e) Copper and aluminium are good conductors of electricity also they have low resistivity. So they are usually used for electricity transmission.