Combining Resistors in Series & Parallel Video Lessons

Concept

Problem: Consider the circuit shown in (Figure 1). Suppose that R = 70 Ω. What is the equivalent resistance between points a and b?

FREE Expert Solution

Equivalent resistance for resistors in series:

$\overline{){{\mathbf{R}}}_{{\mathbf{eq}}}{\mathbf{=}}{{\mathbf{R}}}_{{\mathbf{1}}}{\mathbf{+}}{{\mathbf{R}}}_{{\mathbf{2}}}{\mathbf{+}}{\mathbf{.}}{\mathbf{.}}{\mathbf{.}}{\mathbf{+}}{{\mathbf{R}}}_{{\mathbf{n}}}}$

Equivalent resistance for 2 resistors in parallel:

$\overline{){{\mathbf{R}}}_{{\mathbf{eq}}}{\mathbf{=}}\frac{{\mathbf{R}}_{\mathbf{1}}{\mathbf{R}}_{\mathbf{2}}}{{\mathbf{R}}_{\mathbf{1}}\mathbf{+}{\mathbf{R}}_{\mathbf{2}}}}$

Label the resistors as follows:

Rand R2 are in series.

R12 = 70 + 30 = 100Ω

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Problem Details

Consider the circuit shown in (Figure 1). Suppose that R = 70 Ω. What is the equivalent resistance between points a and b?