Question 423: Current Electricity

Question

When two resistance $$\mathrm{R_1}$$ and $$\mathrm{R_2}$$ connected in series and introduced into the left gap of a meter bridge and a resistance of 10 $$\Omega$$ is introduced into the right gap, a null point is found at 60 cm from left side. When $$\mathrm{R_1}$$ and $$\mathrm{R_2}$$ are connected in parallel and introduced into the left gap, a resistance of 3 $$\Omega$$ is introduced into the right gap to get null point at 40 cm from left end. The product of $$\mathrm{R_1}$$ $$\mathrm{R_2}$$ is ____________$$\Omega^2$$

Accepted Answer

As per given information
$${{{R_1} + {R_2}} \over {10}} = {{0.6} \over {0.4}}$$ ...... (1)
& $${{{{{R_1}{R_2}} \over {{R_1} + {R_2}}}} \over 3} = {{0.4} \over {0.6}}$$ ..... (2)
$$ \Rightarrow \left. \matrix{
  {R_1} + {R_2} = 15 \hfill \cr 
  \& \,{R_1}{R_2} = 30 \hfill \cr}  \right] \Rightarrow {R_1}{R_2} = 30\,{\Omega ^2}$$

Current Electricity

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