A) \[{{l}_{1}}+{{l}_{2}}\]
B) \[\frac{{{l}_{1}}{{l}_{2}}}{{{l}_{1}}+{{l}_{2}}}\]
C) \[\frac{1}{{{l}_{1}}+{{l}_{2}}}\]
D) \[\frac{1}{{{l}_{1}}}+\frac{1}{{{l}_{2}}}\]
Correct Answer: B
Solution :
For parallel combination \[\frac{1}{{{R}_{eff}}}=\frac{1}{{{R}_{1}}}+\frac{1}{{{R}_{2}}}\] \[\Rightarrow \] \[\frac{\pi {{r}^{4}}}{8\eta l}=\frac{\pi {{r}^{4}}}{8\eta {{l}_{1}}}+\frac{\pi {{r}^{4}}}{8\eta {{l}_{2}}}\]\[\Rightarrow \]\[\frac{1}{l}=\frac{1}{{{l}_{1}}}+\frac{1}{{{l}_{2}}}\] \[\therefore \] \[l=\frac{{{l}_{1}}{{l}_{2}}}{{{l}_{1}}+{{l}_{2}}}\]You need to login to perform this action.
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