Resistance of $100 \, cm$ long potentiometer wire is $10 \, \Omega$. It is connected to a battery of $2 \, V$ and a resistance $R$ in series. $A$ source of $10 \, mV$ gives a null point at $40 \, cm$ length. The value of external resistance $R$ is ........... $\Omega$.

Two cells of e.m.f.s $E_1$ and $E_2$ $(E_1 > E_2)$ are connected as shown in the figure. When the potentiometer is connected between $A$ and $B$,the balancing length of the potentiometer wire is $3.60 \ m$. On connecting the potentiometer between $A$ and $C$,the balancing length is $0.90 \ m$. The ratio $E_1 / E_2$ is

The balancing length for a cell is $560 \, cm$ in a potentiometer experiment. When an external resistance of $10 \, \Omega$ is connected in parallel to the cell, the balancing length changes by $60 \, cm$. The internal resistance of the cell in ohms, is

In a potentiometer experiment,cells of e.m.f. $E_{1}$ and $E_{2}$ are connected in series $(E_{1} > E_{2})$,and the balancing length is $64 \ cm$. If the polarity of $E_{2}$ is reversed,the balancing length becomes $32 \ cm$. The ratio $\frac{E_{1}}{E_{2}}$ is:

While doing an experiment with a potentiometer as shown in the figure,it was found that the deflection is one-sided and $(i)$ the deflection decreased while moving the jockey from one end $A$ of the wire to the end $B$; $(ii)$ the deflection increased while the jockey was moved towards the end $B$.
$(i)$ Which terminal ($+$ or $-ve$) of the cell $E_1$ is connected at $X$ in case $(i)$ and how is $E_1$ related to $E$?
$(ii)$ Which terminal of the cell $E_1$ is connected at $X$ in case $(ii)$?

The given potentiometer has its wire of resistance $10\, \Omega$. When the sliding contact is in the middle of the potentiometer wire,the potential drop across the $2\, \Omega$ resistor is -