How can we measure the potential difference across the ends of a conductor?

In a Voltaic cell,what is the direction of the flow of electrons in the external circuit?

What is the equivalent resistance between points $A$ and $B$ in the given electrical circuit (in $Omega$)?

Find out the following in the electric circuit given in the figure:
$(a)$ Effective resistance of two $8\,\Omega$ resistors in the combination.
$(b)$ Current flowing through the $4\,\Omega$ resistor.
$(c)$ Potential difference across the $4\,\Omega$ resistor.
$(d)$ Power dissipated in the $4\,\Omega$ resistor.
$(e)$ Difference in ammeter readings,if any.

Who discovered the electron?

When three resistors of $5 \Omega$,$10 \Omega$,and $30 \Omega$ are connected in parallel in a circuit,what will be the equivalent resistance?