AP Physics 2 / Unit 11: Electric Circuits
11.3 Resistance, Resistivity, and Ohm's Law
Notes
$$V=IR,\qquad R=\frac{\rho L}{A}$$
- Longer, thinner wires have more resistance.
Practice
$V=12$ V, $R=4$ Ω. $I=$
$\displaystyle \frac{12}{4}$.
Doubling a wire's length makes its resistance:
$R\propto L$.
Doubling a wire's cross-sectional area makes its resistance:
$\displaystyle R\propto\frac{1}{A}$.
Ready for more? Take the Unit 11 test.