Resistor

Definition

A resistor is a passive electrical component that opposes the flow of electric current, resulting in a drop in voltage. It is characterized by its resistance, measured in ohms ($\Omega$).

5 Must Know Facts For Your Next Test

1. In AC circuits, resistors impede current equally at all frequencies.
2. The power dissipated by a resistor is given by $P = I^2 R$ where $P$ is power, $I$ is current, and $R$ is resistance.
3. Resistors do not change the phase difference between voltage and current in an AC circuit.
4. The total resistance in a series circuit is the sum of individual resistances: $R_{total} = R_1 + R_2 + ... + R_n$.
5. In a parallel circuit, the reciprocal of the total resistance is the sum of reciprocals of individual resistances: $\frac{1}{R_{total}} = \frac{1}{R_1} + \frac{1}{R_2} + ... + \frac{1}{R_n}$.

Review Questions

• How does a resistor affect current and voltage in an AC circuit?
• What formula represents the power dissipated by a resistor?
• How do you calculate total resistance in a series circuit?

Related terms

Impedance:

The measure of opposition that a circuit presents to the passage of alternating current, denoted as $Z$, and measured in ohms ($\Omega$).

Reactance:

The opposition to alternating current due to capacitance or inductance, causing phase shifts between voltage and current.

$Ohm's\ Law$: $V = IR$, where $V$ is voltage, $I$ is current, and $R$ is resistance.