## Conceptual Physics (12th Edition)

The equation is not given in this textbook, but for 2 resistors in parallel, the following relation holds. $$\frac{1}{R_{parallel}} = \frac{1}{R_{1}} + \frac{1}{R_{2}}$$ Apply the equation to this problem. $$\frac{1}{R_{parallel}} = \frac{1}{40 \Omega} + \frac{1}{40 \Omega } = \frac{1}{20 \Omega}$$ $$R_{parallel} = 20 \Omega$$