Resistance

Definition

Resistance is a measure of how much an object opposes the flow of electric current. It is measured in ohms ($\Omega$).

5 Must Know Facts For Your Next Test

1. Resistance is calculated using Ohm's Law: $R = \frac{V}{I}$, where $R$ is resistance, $V$ is voltage, and $I$ is current.
2. The resistance of a material depends on its resistivity, length, and cross-sectional area: $R = \rho \frac{L}{A}$.
3. Materials with high resistivity have higher resistance; conductors have low resistivity while insulators have high resistivity.
4. Temperature affects resistance; for most materials, resistance increases with increasing temperature.
5. Resistors are components specifically designed to provide a precise amount of resistance in electrical circuits.

Review Questions

• How does Ohm's Law relate voltage, current, and resistance?
• What factors determine the resistance of a wire?
• How does temperature generally affect the resistance of most materials?

Related terms

Ohm's Law:

A fundamental principle stating that the current through a conductor between two points is directly proportional to the voltage across the two points: $V = IR$.

Resistivity:

A material-specific property that quantifies how strongly it resists electric current flow. It is denoted by $\rho$ and measured in ohm-meters ($\Omega \cdot m$).

Conductor:

A material with low resistivity that allows electric current to flow easily through it.