By increasing the temperature,the specific resistance of a conductor and a semiconductor respectively

At room temperature $(27.0^{\circ} C)$,the resistance of a heating element is $100\; \Omega$. What is the temperature (in $^{\circ} C$) of the element if the resistance is found to be $117\; \Omega$,given that the temperature coefficient of the material of the resistor is $1.70 \times 10^{-4}\; ^{\circ} C^{-1}$?

The specific resistance (resistivity) of material $B$ is twice that of material $A$. Two wires are prepared from these materials having the same resistance. If the diameter of wire $B$ is twice the diameter of wire $A$,then the ratio of the lengths of the two wires $l_B / l_A$ is equal to ......

The resistivity of iron is $1 \times 10^{-7} \, \Omega \cdot m$. The resistance of an iron wire of a particular length and thickness is $1 \, \Omega$. If the length and the diameter of the wire are both doubled, then the resistivity in $\Omega \cdot m$ will be:

An aluminium (resistivity $\rho = 2.2 \times 10^{-8} \Omega \cdot m$) wire of diameter $1.4 \text{ mm}$ is used to make a $4 \Omega$ resistor. The length of the wire is: (in $\text{ m}$)

The unit of specific resistance is