Resistance

High School

Definition

A measure of how strongly a material opposes the flow of electric current, measured in ohms. Higher resistance reduces current for a given voltage, and resistance often converts electrical energy into heat.

Worked examples

\(R = 100 \, \Omega\)

A resistor with 100 ohms of resistance opposes current flow; the symbol Ω represents ohms.

\(V = IR \)→\( I = \frac{V}{R} = \frac{12 \, \)V\(}{6 \, \Omega} = 2 \, \)A\(\)

Higher resistance reduces current; here 6 Ω limits a 12 V source to 2 A of current.

A thin wire has higher resistance than a thick wire of the same material and length.

Less cross-sectional area makes it harder for electrons to flow, increasing resistance.

Common mistakes

More resistance means more current flows → More resistance means less current flows for a given voltage Resistance opposes current; higher resistance reduces current (Ohm's law: I = V/R).
Resistance and resistivity are the same thing → Resistivity is a material property; resistance depends on size and shape too Resistance = resistivity × length / area; a material's resistivity is intrinsic, resistance is not.
\(R = \frac{I}{V}\) → \(R = \frac{V}{I}\) Ohm's law is V = IR, so resistance is voltage divided by current, not the reverse.

Where you'll use it next

You'll use resistance when analyzing series and parallel circuits, calculating power dissipation and heat in components, designing electrical devices, and studying Ohm's law in physics and engineering courses.

Found in 1 StudyPug lesson

Understanding Electrical Resistance: From Basics to Advanced Applications

Physics 11

Dive into the world of electrical resistance. Master key concepts, calculations, and real-world applications. Boost your understanding of circuits and power systems with our comprehensive guide.

11th Grade11th