- $ r_{eq} = \Delta \frac{r_1 r_2}{r_1+r_2} \text { Equivalent } $
- $ \text { resistance for }$ $ r_1 || r_2 $
- $ \varepsilon_{eq}=\frac{\varepsilon_1 r_2+\varepsilon_2 r_1}{r_1+r_2} $
- $ =\left[\frac{\varepsilon_1 r_2+\varepsilon_2 r_1}{r_1 r_2}\right] \times \frac{r_1 r_2}{r_1+r_2}$
- $ =\left(\frac{\varepsilon_1}{r_1}+\frac{\varepsilon_1}{r_2}\right) \times r_{eq}$
- $ \frac{\varepsilon_{eq}}{r_{eq}}=\frac{\varepsilon_1}{r_1}+\frac{\varepsilon_2}{r_2}$
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