$($b$)$ Figure $2$ shows in potentioneter with a cell of emf $2\mathrm{.}0$ V and intemal resistance $0\mathrm{.}4$ maintaining a potential drop across the resistance wire AB$.$ A standard cell that maintains a constant emf of $1\mathrm{.}02$ V $($for very moderate currents up to a few uA$)$ gives a balance point at $67\mathrm{.}3$ cm length of the wire. To ensure a shallow current is drawn from the standard cell, a very high resistance of $600k$ is put in series, which is sherted close to the balance point. The standard cell is then replaced by a cell of unknown emf$($e$)$ and the balance point found, similarly, turns out to be at $82\mathrm{.}3$ cm length of wax wuc.

i$)$ What is the value of $$

ii$)$ What purpose of the high resistance of $600k$

iii$)$ is the balance point affected by this high resistance?

iv$)$ Is the balance point affected by the internal resistance of the driver cell?

v$)$ Would the method work in the above situation if the driver cell of the potentiometer had an e$.$m$.$f$.$ of $1\mathrm{.}0V$ instead of $2\mathrm{.}0$ V

vi$)$ Would the circuit work well for determining an extremely sinall c$.$m$.$f$.,$ say of the order of a few mV $($such as the typical e$.$m$.$f$.$ of a thernocouple$)$ If not, how will you modify the circuit?