In the given arrangement of experiment on meter bridge, if $$A D$$ corresponding to null deflection of the galvanometer is $$X$$, what would be its value if the radius of the wire $$A B$$ is doubled?

A copper wire of length $$1 \mathrm{~m}$$ and uniform cross-sectional area $$5 \times 10^{-7} \mathrm{~m}^2$$ carries a current of $$1 \mathrm{~A}$$. Assuming that, there are $$8 \times 10^{28}$$ free electrons per $$\mathrm{m}^3$$ in copper, how long will an electron take to drift from one end of the wire to the other?

Consider an electrical conductor connected across a potential difference $$V$$. Let $$\Delta q$$ be a small charge moving through it in time $$\Delta t$$. If $$I$$ is the electric current through it,

I. the kinetic energy of the charge increases by $$I V \Delta t$$.

II. the electric potential energy of the charge decreases by $$I V \Delta t$$.

III. the thermal energy of the conductor increases by $$I V \Delta t$$.

Choose the correct option.

A metal rod of length $$10 \mathrm{~cm}$$ and a rectangular cross-section of $$1 \mathrm{~cm} \times \frac{1}{2} \mathrm{~cm}$$ is connected to a battery across opposite faces. The resistance will be