Power $P$ is to be delivered to a device via transmission cables having resistance $R_c$. If $V$ is the voltage across $R$ and $I$ is the current through It, find the power wasted and how can It be reduced?

AB is a potentiometer wire (Figure). If the value of $R$ is increased, In which direction will the balance point $\mathrm{J}$ shift?

While doing an experiment with potentiometer (Figure) It was found that the deflection Is one sided

(a) the deflection decreased while moving from one end A of the wire to the end B.

(b) the deflection Increased, while the Jockey was moved towards the end B.

(i)  Which terminal $+\mathrm{or} -\mathrm{ve}$ of the cell $E_1$ is connected at $X$ in case (a) and how is $E_1$ related to $E$ 

(ii) Which terminal of the cell $E_1$ is connected at $X$ in case (b)?

The circuit in Figure shows two cells connected In opposition to each other. Cell $E_1$ is of emf $6\mathrm{V}$ and Internal resistance $2\mathrm{\Omega }$; the cell $E_2$ is of emf $4\mathrm{V}$ and Internal resistance $8\mathrm{\Omega }$. Find the potential difference between the points A and B.

Two cells of same emf $\mathrm{E}$ but internal resistance $r_1$; and $r_2$ are connected in series to an external resistor $R$(Figure)What should be the value of $R$so that the potential difference across the terminals of the first cell becomes zero ?