Resistances $$R_1$$ and $$R_2$$ are in the ratio $$1 \colon 2$$. Equivalent resistance between A and B is $$8\,\Omega$$. Find $$R_1$$ and $$R_2$$. If $$R_1$$ is now doubled and a potential difference of $$20\text{ V}$$ is applied between A and B find the current flowing from A to B
[image]

PLACEHOLDER ANSWER - the question has three answers. With $$R_2 = 2R_1$$ in parallel, $$R_1 \parallel R_2 = \frac{2R_1}{3}$$, and this is in series with $$4\,\Omega$$, so $$4 + \frac{2R_1}{3} = 8$$. This gives $$R_1 = 6\,\Omega$$ and $$R_2 = 12\,\Omega$$. When $$R_1$$ becomes $$12\,\Omega$$, the parallel pair is $$6\,\Omega$$, the total is $$10\,\Omega$$, and the current is $$\frac{20}{10} = 2\text{ A}$$.