Internal Resistance Questions

A current of $2\text{A}$ flows through a $2\Omega$ resistor when connected across a battery. The same battery supplies a current of $0.5\text{A}$ when connected across a $9\Omega$ resistor. The internal resistance of the battery is:

A cell can be balanced against $110\text{cm}$ and $100\text{cm}$ of potentiometer wire, respectively with and without being short circuited through a resistance of $10\Omega$. Its internal resistance is:

A student measures the terminal potential difference ($V$) of a cell (of emf $ϵ$ and internal resistance $r$) as a function of the current ($I$) flowing through it. The slope and intercept of the graph between $V$ and $I$ are respectively:

A cell with emf $ϵ$ and internal resistance $r$ is connected to variable $R$. Plot of potential difference $V$ across $R$ vs $R$ is:

The internal resistance of a $2.1\text{V}$ cell which gives a current of $0.2\text{A}$ through a resistance of $10\Omega$ is: