A battery of e.m.f. E and internal resistance r is connected to an external resistance R the condition for maximum power transfer is

A thin wire of resistance 4 $$\Omega$$ is bent to form a circle. The resistance across any diameter is

Consider a circuit where a cell of emf $$E_0$$ and internal resistance $$\mathrm{r}$$ is connected across the terminal $$\mathrm{A}$$ and $$\mathrm{B}$$ as shown in figure. The value of $$\mathrm{R}$$ for which the power generated in the circuit is maximum, is given by

In an experiment on a circuit as shown in the figure, the voltmeter shows 8 V reading. The resistance of the voltmeter is,