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The series combination of two batteries, both of the same emf 10 V , but different internal resistance of 20 \Omega and 5 \Omega , is connected to the parallel combination of two resistors 30 \Omega and R \Omega . The voltage difference across the battery of internal resistance 20 \Omega is zero, the value of R (in \Omega ) is __________ .
Option: 1 30
Option: 2 60
Option: 3 90
Option: 4 45
 

Answers (1)

best_answer

 

 

 

 

 

\begin{array}{l}{\mathrm{V}_{1}=\varepsilon_{1}-\mathrm{i} . \mathrm{r}_{1}} \\ {0=10-\mathrm{i} \times 20} \\ {\mathrm{i}=0.5 \mathrm{A}} \\ {\mathrm{V}_{2}=\varepsilon_{2}-\mathrm{ir}_{2}} \\ {=10-0.5 \times 5} \\ {\mathrm{V}_{2}=7.5 \mathrm{V}} \\ {\mathrm{O} \cdot 5=\frac{7.5}{30}+\frac{7.5}{\mathrm{x}}} \\ {\frac{7.5}{x}=0.25} \\ {x=\frac{7.5}{0.25}=30}\end{array}

Hence option (1) is correct. 

Posted by

vishal kumar

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