The resistance of an incandescent lamp is

The new resistance of a wire of $R \, \Omega$,whose radius is reduced to half,is

Masses of three wires of copper are in the ratio $1:3:5$ and their lengths are in the ratio $5:3:1$. The ratio of their electrical resistances is:

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

Two different conductors have the same resistance at $0\,^{\circ}C.$ It is found that the resistance of the first conductor at $t_1\,^{\circ}C$ is equal to the resistance of the second conductor at $t_2\,^{\circ}C.$ The ratio of the temperature coefficients of resistance of the conductors,$\frac{\alpha_1}{\alpha_2}$ is

For a metallic wire,the ratio of voltage to corresponding current is