Question

How to calculate internal resistance in both series and parallel circuit?

Answer 1

in series
R_{\rm eq} = R_1 + R_2.

Answer 2

\begin{displaymath} \frac{1}{R_{\rm eq}} = \frac{1}{R_1} + \frac{1}{R_2}. \end{displaymath}
in parallel circuit

Answer 3

\[\frac{ 1 }{ \Re }=\frac{ 1 }{ R1 }+\frac{ 1 }{ R2 }\]

Answer 4

http://en.wikibooks.org/wiki/A-level_Physics_%28Advancing_Physics%29/Internal_Resistance
THIS MAY HELP YOU
http://farside.ph.utexas.edu/teaching/302l/lectures/node58.html

Answer 5

thank you.