Question

$AB$ is a wire of uniform resistance. The galvanometer $G$ shows no current when the length $AB \,= 20\, cm$ and $BC\, = 80\, cm$. The resistance $R$ is equal to

• A. $20\, \Omega $
• B. $80\, \Omega $
• C. $10\, \Omega $
• D. $40\, \Omega $

Answer 1

Answer: (A)

For $ \frac{{{R}_{1}}}{{{R}_{2}}}=\frac{{{L}_{1}}}{{{L}_{2}}} $
$ \Rightarrow $ $ {{R}_{1}}=\frac{{{L}_{1}}}{{{L}_{2}}}\times {{R}_{2}}=\frac{20}{80}\times 80=20\,\Omega $