Question 24.9: In Fig. 24.14, let R1 = 6 Ω, R2 = 3 Ω, and ΔV = 18 V. Find I......

The equivalent resistance of the series combination is:
R_{eq}  =  R_{1}  +  R_{2} = 6 Ω + 3 Ω = 9 Ω

Using Ohm’s law, given by Eq. 24.16, we find:

ΔV = I R \left\{\begin{matrix} Equivalent  form\\ of  Ohm’s  law\end{matrix}\right\}            (24.16)

I={\frac{\Delta V}{R_{\mathrm{eq}}}}={\frac{18\,\mathrm{V}}{9\,\Omega}}=2\,\mathrm{A}

ΔV_{1}  =  IR_{1} = (2A)(6 Ω) = 12 V
ΔV_{2}  =  IR_{2} = (2 A)(3 Ω) = 6 V