What is the advantage of using thick metallic strips to join wires in a potentiometer?

$AB$ is a potentiometer wire (See figure). If the value of $R$ is increased, in which direction will the balance point $J$ shift?

While doing an experiment with a potentiometer (see figure) it was found that $\left(\mathrm{i}\right)$ the deflection is one-sided and $\left(\mathrm{ii}\right)$ the deflection decreased while moving from one end $A$ of the wire to the other end $B$.

Which terminal (positive or negative) of the cell $E_1$ is connected at $X$ in case $\left(\mathrm{ii}\right)$ and how is $E_1$ related to $E$?

While doing an experiment with the potentiometer (see figure) it was found that $\left(\mathrm{i}\right)$ the deflection is one-sided, $\left(\mathrm{ii}\right)$ the deflection decreased while moving from one end $A$ of the wire to the other end $B$ and $\left(\mathrm{iii}\right)$ the deflection increased while the jockey was moved towards the end $B$.
  

 Which terminal of the cell $E_1$ is connected at $X$ in case $\left(\mathrm{i}\right)$?