Ohm's law:

$\overline{){\mathbf{I}}{\mathbf{=}}\frac{\mathbf{V}}{\mathbf{R}}}$

The current flowing in each circuit is expressed as:

I_{0} = V_{b}/R_{U}

I_{1} = V_{b}/(R_{r }+ R_{U})

An ammeter is connected in series to a battery of voltage V_{b} and a resistor of unknown resistance R_{u} (Figure 1) . The ammeter reads a current I_{o}. Next, a resistor of unknown resistance R_{r} is connected in series to the ammeter, and the ammeter's reading drops to I_{1}. Finally, a second resistor, also of resistance R_{r}, is connected in series as well. Now the ammeter reads I_{2}.

If I_{1}/I_{0}=4/5, find I_{2}/I_{0}.

Express the ratio I_{2}/I_{0} numerically.

I_{2}/I_{0} =

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