The resistivity of semiconductor materials is $..........$.

State $Ohm's$ law. How can it be verified?

An electric bulb should be connected to how much voltage line if it draws an electric current of $0.5\, A$,the resistance of the filament of that bulb being $440\, \Omega$ (in $, V$)?

$(a)$ $A$ Nichrome wire of length $L$ and radius $r$ has a resistance of $10 \, \Omega$. How would the resistance of the wire change when:
$(i)$ only the length of the wire is doubled?
$(ii)$ only the diameter of the wire is doubled? Justify your answer.
$(b)$ Why are the elements of electrical heating devices made up of alloys?

State the factors on which the resistance of a cylindrical conductor depends. How will the resistance of a conductor change if it is stretched so that its length is doubled?

Name and define the $SI$ unit of resistance. Calculate the resistance of a resistor if the current flowing through it is $200\, mA$, when the applied potential difference is $0.8\, V$.