Q 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? (e) Why are copper and aluminium wires usually employed for electricity transmission? Chapter 12: Electricity Science Class 10 solutions are developed for assisting understudies with working on their score and increase knowledge of the subjects. Why is the tungsten used almost exclusively for filament of electric lamps, Why are the conductors of electric heating devices, such as bread-toasters and electric irons, made of an alloy rather than a pure metal, Why is the series arrangement not used for domestic circuits, 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 is solved by our expert teachers. You can get ncert solutions and notes for class 10 chapter 12 absolutely free. NCERT Solutions for class 10 Science Chapter 12: Electricity is very essencial for getting good marks in CBSE Board examinations
Q 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?
(e) Why are copper and aluminium wires usually employed for electricity transmission?
Answer:
(a) Tungsten is an alloy which has very high melting point and very high resistivity so does not burn easily at a high temperature.
(b) 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.
(c) In series circuits voltage is divided. Each component of a series circuit receives a small voltage so the amount of current decreases and the device becomes hot and does not work properly. Hence, series arrangement is not used in domestic circuits.
(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.
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