Resistance

Definition

Resistance is a measure of the opposition to the flow of electric current in a material. It is measured in ohms ($\Omega$).

5 Must Know Facts For Your Next Test

1. The resistance $R$ of a conductor is given by Ohm's Law: $V = IR$, where $V$ is voltage, $I$ is current.
2. Resistors in series add up ($R_{total} = R_1 + R_2 + ... + R_n$) while resistors in parallel have a reciprocal sum ($\frac{1}{R_{total}} = \frac{1}{R_1} + \frac{1}{R_2} + ... + \frac{1}{R_n}$).
3. Factors affecting resistance include material type, length, cross-sectional area, and temperature.
4. The SI unit for resistance is the ohm ($\Omega$), named after Georg Simon Ohm.
5. A perfect conductor has zero resistance, while an insulator ideally has infinite resistance.

Review Questions

• What equation relates voltage, current, and resistance?
• How do you calculate the total resistance for resistors arranged in series?
• Which factors influence the amount of resistance in a wire?

Related terms

Ohm's Law:

A fundamental principle stating that $V = IR$, where $V$ is voltage, $I$ is current, and $R$ is resistance.

Resistor:

A passive electrical component that implements electrical resistance as a circuit element.

Series Circuit:

An electrical circuit in which components are connected end-to-end so that current flows through each component sequentially.