You are given a resistance wire of length $50 \,cm$ and a battery of negligible resistance. In which of the following cases is the largest amount of heat generated?

The electrical resistivity of a few materials is given below in ohm-metre. Which of these materials can be used for making the element of a heating device?

$A$. $6.84 \times 10^{-8} \, \Omega m$

$B$. $1.60 \times 10^{-8} \, \Omega m$

$C$. $1.00 \times 10^{-4} \, \Omega m$

$D$. $2.50 \times 10^{12} \, \Omega m$

$E$. $4.40 \times 10^{-5} \, \Omega m$

$F$. $2.30 \times 10^{17} \, \Omega m$

$(a)$ Why is the series arrangement not used for domestic circuits?
$(b)$ Why is tungsten used almost exclusively for the filament of electric lamps?
$(c)$ Why are the conductors of electric heating devices,such as bread toasters and electric irons,made of an alloy rather than a pure metal?
$(d)$ Why are copper and aluminium wires usually employed for electricity transmission?
$(e)$ Why does the cord of an electric heater not glow while the heating element does?

Two lamps,one rated $100\, W$ at $220\, V$,and the other $60\, W$ at $220\, V$,are connected in parallel to electric mains supply. What current (in $A$) is drawn from the line if the supply voltage is $220\, V$?

Elements of electric toasters and electric irons are made of an alloy rather than a pure metal. Give two reasons to justify the statement.

What is the practical unit used for electrical energy?