A battery source of 20 V when connected to a load of 19Ω draws a current of 1 A. What is the value of internal resistance of battery?

Correct option is D

$$V = I \times (R + r) \\[8pt]\text{Where:} \\[4pt]\bullet \; V \text{ is the total voltage} \\[4pt]\bullet \; I \text{ is the current} \\[4pt]\bullet \; R \text{ is the load resistance} \\[4pt]\bullet \; r \text{ is the internal resistance of the battery} \\[8pt]\textbf{Calculation:} \\[4pt]\text{Given:} \\[4pt]\bullet \; V = 20\,\text{V} \\[4pt]\bullet \; R = 19\,\Omega \\[4pt]\bullet \; I = 1\,\text{A} \\[8pt]\text{Using the formula:} \\[4pt]20 = 1 \times (19 + r) \\[4pt]20 = 19 + r \\[4pt]r = 20 - 19 \\[4pt]r = 1\,\Omega$$​​