Why are coils of electric toasters and electric irons made of an alloy rather than a pure metal?
The coils of electric toasters and electric irons are made of an alloy rather than a pure metal primarily due to their specific electrical and physical properties. The resistivity of an alloy is generally higher than that of its constituent metals, which makes them suitable for generating the necessary heat in heating devices.
Furthermore, alloys do not oxidise (burn) readily at high temperatures. Since these appliances operate at very high temperatures, the material must withstand heat without degrading. Pure metals might oxidise faster, but alloys provide the required stability and longevity for such applications.
Explanation
The textbook explicitly states two key reasons for using alloys in heating devices. First, Table 11.2 indicates that the resistivity of an alloy is generally higher than that of its constituent metals. Second, the text notes that alloys do not oxidise (burn) readily at high temperatures. These properties make them ideal for devices like electric irons and toasters which generate significant heat during operation.