The conductivity of a superconductor is

An electric toaster has a resistance of $60 \ \Omega$ at room temperature $\left(27^{\circ} C\right)$. The toaster is connected to a $220 \ V$ supply. If the current flowing through it reaches $2.75 \ A$,the temperature attained by the toaster is around: (given $\alpha = 2 \times 10^{-4} /{ }^{\circ} C$) (in $^{\circ} C$)

There are two wires of the same length and of the same material and radii $r$ and $2r$. The ratio of their specific resistance is

The length of the wire is doubled. Its conductance will be

The resistivity of a wire:

The resistance of a wire is $20 \, \Omega$. It is stretched such that its length becomes three times its original length. The new resistance of the wire will be ............. $ \Omega$.