The terminal potential difference of a cell when short-circuited is ($E$ = $E.M.F.$ of the cell).

Four identical cells, each of $2 \, V$ e.m.f., are connected in parallel. They supply current to an external circuit consisting of two $15 \, \Omega$ resistors connected in parallel. The terminal voltage of the equivalent cell, as measured by an ideal voltmeter, is $1.6 \, V$. Calculate the internal resistance of each cell in $\Omega$.

Ten identical cells each emf $2 \, V$ and internal resistance $1 \, \Omega$ are connected in series with two cells wrongly connected. $A$ resistor of $10 \, \Omega$ is connected to the combination. What is the current through the resistor (in $ \, A$)?

When an external resistance of $5\text{ }\Omega$ is connected across the terminals of a cell,a current of $0.25\text{ A}$ flows through it. When the $5\text{ }\Omega$ resistor is replaced by a $2\text{ }\Omega$ resistor,a current of $0.5\text{ A}$ flows through it. The internal resistance of the cell is . . . . . . $\Omega$.

Who among the following scientists made the statement "Chemical change can produce electricity"?

Why is the combination of cells done? Write its methods.