A) \[6\,\,\Omega \]
B) \[3\,\,\Omega \]
C) \[9\,\,\Omega \]
D) \[15\,\,\Omega \]
Correct Answer: B
Solution :
When cell is giving current (i), then the potential difference V across its plates is less than the emf E of the cell, its reason is the internal resistance (r) in the cell. Therefore, \[V=E-ir\] \[\Rightarrow \] \[r=\left( \frac{E}{V}-1 \right)R\] \[\left( \because \,\,i=\frac{V}{R} \right)\] Given, \[E=40\,V,\,V=30\]volt, \[R=9\,\Omega \] \[\therefore \] \[r=\left( \frac{40}{30}-1 \right)\times 9\] \[=\frac{9\times 10}{30}\,3\,\Omega \]= Note: The emf (E) is the characteristic of each cell and its value remains constant for the cell, while the potential difference (V) goes on decreasing on taking more and more current from the cell.
You need to login to perform this action.
You will be redirected in
3 sec
