ohm

(noun)

in the International System of Units, the derived unit of electrical resistance; the electrical resistance of a device across which a potential difference of one volt causes a current of one ampere; symbol: Ω

Related Terms

  • electrical current
  • ampere

Examples of ohm in the following topics:

  • Ohm's Law

    • This important relationship is known as Ohm's law.
    • The unit for resistance is the ohm where 1Ω = 1 V/A.
    • This relationship is also called Ohm's law.
    • Ohm's law (like Hooke's law) is not universally valid.
    • The other two devices do not follow Ohm's law.
  • Current and Voltage Measurements in Circuits

    • According to Ohm's law, The electrical current I, or movement of charge, that flows through most substances is directly proportional to the voltage V applied to it.
    • Ohm's law can therefore be written as follows:
    • More specifically, Ohm's law states that R in this relation is constant, independent of the current.
    • To solve this problem, we would just substitute the given values into Ohm's law: I = 1.5V/5Ω; I = 0.3 amperes.
    • If we know the current and the resistance, we can rearrange the Ohm's law equation and solve for voltage V:
  • Resistors in AC Circuits

    • In a circuit with a resistor and an AC power source, Ohm's law still applies (V = IR).
    • Ohm's law applies to AC circuits as well as to DC circuits.
    • Apply Ohm's law to determine current and voltage in an AC circuit
  • Capacitors in AC Circuits: Capacitive Reactance and Phasor Diagrams

    • There, we used the Ohm's law (V=IR) to derive the relationship between voltage and current in AC circuits.
    • In this and following Atoms, we will generalize the Ohm's law so that we can use it even when we have capacitors and inductors in the circuit.
    • Because it is still a voltage divided by a current (like resistance), its unit is the ohm.
    • This is considered to be an effective resistance of the capacitor to AC, and so the rms current Irms in the circuit containing only a capacitor C is given by another version of Ohm's law to be $I_{rms} = \frac{V_{rms}}{X_C}$, where Vrms is the rms voltage.
    • Note that XC replaces R in the DC version of the Ohm's law.
  • Resisitors in Series

    • Using Ohm's Law to Calculate Voltage Changes in Resistors in Series
    • According to Ohm's law, the voltage drop, V, across a resistor when a current flows through it is calculated by using the equation V=IR, where I is current in amps (A) and R is the resistance in ohms (Ω).
  • Resistors in Parallel

    • According to Ohm's law, the currents flowing through the individual resistors are $I_1 = \frac{V}{R_1}$, $I_2 = \frac{V}{R_2}$, and $I_3 = \frac{V}{R_3}$.
  • Inductors in AC Circuits: Inductive Reactive and Phasor Diagrams

    • The rms current Irms through an inductor L is given by a version of Ohm's law: $I_{rms} = \frac{V_{rms}}{X_L}$ where Vrms is the rms voltage across the inductor and $X_L = 2\pi \nu L$ with $\nu$ the frequency of the AC voltage source in hertz.
    • Because the inductor reacts to impede the current, XL has units of ohms (1 H=1 Ωs, so that frequency times inductance has units of (cycles/s)(Ωs)=Ω), consistent with its role as an effective resistance.
  • Introduction and Importance

    • Kirchhoff, rather, used Georg Ohm's work as a foundation for Kirchhoff's current law (KCL) and Kirchhoff's voltage law (KVL).
  • RLC Series Circuit: At Large and Small Frequencies; Phasor Diagram

    • By combining Ohm's law (Irms=Vrms/Z; Irms and Vrms are rms current and voltage) and the expression for impedance Z, from:
  • Poiseuille's Equation and Viscosity

    • Poiseuille's equation as given in this example (see ) is analogous to Ohm's equation for determining the resistance in an electronic circuit and is of great practical use in hydraulic-circuit analysis.
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