$A$ heating element has a resistance of $100\,\Omega$ at room temperature. When it is connected to a supply of $220\,V$,a steady current of $2\,A$ passes through it and the temperature is $500\,^{\circ}C$ higher than room temperature. What is the temperature coefficient of resistance of the heating element?

Choose the correct alternative:
$(a)$ Alloys of metals usually have (greater/less) resistivity than that of their constituent metals.
$(b)$ Alloys usually have much (lower/higher) temperature coefficients of resistance than pure metals.
$(c)$ The resistivity of the alloy manganin is nearly independent of/ increases rapidly with increase of temperature.
$(d)$ The resistivity of a typical insulator (e.g.,amber) is greater than that of a metal by a factor of the order of $(10^{22}/10^{23}).$

Resistivity of which of the following substances decreases on increasing the temperature?

$A$ wire of length $1.0\, m$ and diameter $0.6\, cm$ has a resistance of $3.0 \times 10^{-3}\, \Omega$. What will be the resistance between the faces of a disc made of the same material with diameter $2.0\, cm$ and thickness $1.0\, mm$?

$A$ wire of $1 \,\Omega$ has a length of $1\, m$. It is stretched until its length increases by $25\, \%$. The percentage change in resistance to the nearest integer is .....$\%$

Which of the following has a negative temperature coefficient of resistance?