A cell of internal resistance of 2\(\Omega\) supplies current through a resistor, X if the efficiency of the cell is 75%, find the value of X.
- 2\(\Omega\)
- 4\(\Omega\)
-
6\(\Omega\)
- 8\(\Omega\)
The correct answer is: C
Explanation
The efficiency of a cell = \(\frac{\text{Ext. R}}{\text{Ext.R + int. r}}\) x 100
Ext. R = X
int. r = 2\(\Omega\)
Efficiency = 75% = 0.75
0.75 = \(\frac{\text{X}}{\text{X} + 2}\)
0.75( X + 2 ) = X
0.75x + 1.5 = X
0.25X = 1.5
X = \(\frac{1.5}{0.25}\) = 6\(\Omega\)
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