JEE Mains · Physics · STD 12 - Current electricity
- JEE Mains 2019
- Medium
- Numerical
An ideal battery of \(4\, V\) and resistance \(R\) are connected in series in the primary circuit of a potentiometer of length \(1\, m\) and resistance \(5\,\Omega \) . The value of \(R\), to give a difference of \(5\, mV\) across \(10\, cm\) of potentiometer wire, is: ................ \(\Omega\)
Pick an option to check your answer.
Answer & Solution
Correct Answer
(C) \(395\)
Step-by-step Solution
Detailed explanation
\(i=\frac{4}{5+R}\)
\(V_{A B}=i(5)=\frac{20}{5+R}\)
\(V_{A P}=\frac{V_{A B}}{L}(0.1)=\frac{20}{5+R}\left(\frac{0.1}{1}\right)=\frac{2}{5+R}\)
Now, \(\frac{2}{5+R}=5 \times 10^{-3}\)
\(\Rightarrow \quad R=395\, \Omega\)
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