resistor

(noun)

An electric component that transmits current in direct proportion to the voltage across it.

Related Terms

Examples of resistor in the following topics:

  • Resisitors in Series

    • The simplest combinations of resistors are the series and parallel connections.
    • shows resistors in series connected to a voltage source.
    • Using Ohm's Law to Calculate Voltage Changes in Resistors in Series
    • Therefore, resistors connected in series use up the same amount of energy as a single resistor, but that energy is divided up between the resistors depending on their resistances.
    • These four resistors are connected in series because if a current was applied at one end, it would flow through each resistor sequentially to the end.

  • Resistors in Parallel

    • Resistors in a circuit can be connected in series or in parallel.
    • Resistors are in parallel when each resistor is connected directly to the voltage source by connecting wires having negligible resistance.
    • Each resistor thus has the full voltage of the source applied to it .
    • Each resistor draws the same current it would if it were the only resistor connected to the voltage source.
    • Each resistor in the circuit has the full voltage .

  • Combination Circuits

    • More complex connections of resistors are sometimes just combinations of series and parallel.
    • In the initial image, the two circled sections show resistors that are in parallel.
    • The next step shows that the circled two resistors are in parallel.
    • Essentially, wire resistance is a series with the resistor.
    • This combination of seven resistors has both series and parallel parts.

  • Resistance and Resistivity

    • Recall that an object whose resistance is proportional to the voltage and current is known as a resistor .
    • Likewise, resistors range over many orders of magnitude.
    • For the case of two resistors in parallel, this can be calculated using:
    • However, some complex networks of resistors cannot be resolved in this manner.
    • In the special case of N identical resistors all connected in series or all connected in parallel, the power rating of the individual resistors is thereby multiplied by N.

  • Resistors and Capacitors in Series

    • An RC circuit has a resistor and a capacitor and when connected to a DC voltage source, and the capacitor is charged exponentially in time.
    • An RC circuit is one containing a resistor R and a capacitor C.
    • The equation for voltage versus time when charging a capacitor C through a resistor R, is:
    • Discharging a capacitor through a resistor proceeds in a similar fashion, as illustrates.
    • Using calculus, the voltage V on a capacitor C being discharged through a resistor R is found to be

  • Ohm's Law

    • An object that has simple resistance is called a resistor, even if its resistance is small .
    • The resistor is like a pipe that reduces pressure and limits flow because of its resistance.
    • In a simple circuit (one with a single simple resistor), the voltage supplied by the source equals the voltage drop across the resistor, since E=qΔV, and the same q flows through each.
    • The I–V curves of four devices: two resistors, a diode, and a battery.
    • The two resistors follow Ohm's law: The plot is a straight line through the origin.

  • Resistors in AC Circuits

    • In a circuit with a resistor and an AC power source, Ohm's law still applies (V = IR).
    • In this example, in which we have a resistor and the voltage source in the circuit, the voltage and current are said to be in phase, as seen in (b).
    • Current in the resistor alternates back and forth without any phase difference, just like the driving voltage.
    • Consider a perfect resistor that brightens and dims 120 times per second as the current repeatedly goes through zero.

  • Introduction and Importance

    • Consider, for example, the circuit illustrated in the figure below, consisting of five resistors in a combination of in series and parallel arrangements.
    • However, using Kirchhoff's rules, one can analyze the circuit to determine the parameters of this circuit using the values of the resistors (R1, R2, R3, r1 and r2).
    • Thus, although this law can be applied to circuits containing resistors and capacitors (as well as other circuit elements), it can only be used as an approximation to the behavior of the circuit when a changing current and therefore magnetic field are involved.
    • To determine all variables (i.e., current and voltage drops across the different resistors) in this circuit, Kirchhoff's rules must be applied.

  • Impedance

    • Rather than solving the differential equation relating to circuits that contain resistors and capacitors, we can imagine all sources in the circuit are complex exponentials having the same frequency.
    • For the resistor, $v = Ri$.
    • Thus the resistor's voltage is a complex, as is the current with an amplitude $I = \frac{V}{R}$.
    • The impedance of a resistor is R, while that of a capacitor (C) is $\frac{1}{j \omega C}$.
    • In the case of the circuit in , to find the complex impedance of the RC circuit, we add the impedance of the two components, just as with two resistors in series: $Z = R + \frac{ 1}{j \omega C}$.

  • RL Circuits

    • An RL circuit consists of an inductor and a resistor, in series or parallel with each other, with current driven by a voltage source.
    • A resistor-inductor circuit (RL circuit) consists of a resistor and an inductor (either in series or in parallel) driven by a voltage source.
    • When the switch in (a) is moved to position 2 and cuts the battery out of the circuit, the current drops because of energy dissipation by the resistor.
    • When in position 1, the battery, resistor, and inductor are in series and a current is established.
    • In position 2, the battery is removed and the current eventually stops because of energy loss in the resistor.