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The two resistors follow Ohm's law: The plot is a straight line through the origin. The other two devices do not follow Ohm's law. There are, however, components of electrical circuits which do not obey Ohm's law; that is, their relationship between current and voltage (their I – V curve ) is nonlinear (or non-ohmic).
The current–voltage characteristics of four devices: Two resistors, a diode, and a battery. The horizontal axis is voltage drop, the vertical axis is current. Ohm's law is satisfied when the graph is a straight line through the origin. Therefore, the two resistors are ohmic, but the diode and battery are not.
The SI unit of electrical resistivity is the ohm-metre (Ω⋅m). [1] [2] [3] For example, if a 1 m 3 solid cube of material has sheet contacts on two opposite faces, and the resistance between these contacts is 1 Ω, then the resistivity of the material is 1 Ω⋅m.
For example, a 10 ohm resistor connected in parallel with a 5 ohm resistor and a 15 ohm resistor produces 1 / 1/10 + 1/5 + 1/15 ohms of resistance, or 30 / 11 = 2.727 ohms. A resistor network that is a combination of parallel and series connections can be broken up into smaller parts that are either one or the other.
One of the functions of many types of multimeters is the measurement of resistance in ohms.. The ohm is defined as an electrical resistance between two points of a conductor when a constant potential difference of one volt (V), applied to these points, produces in the conductor a current of one ampere (A), the conductor not being the seat of any electromotive force.
Figure 1: Schematic of an electrical circuit illustrating current division. Notation R T refers to the total resistance of the circuit to the right of resistor R X.. In electronics, a current divider is a simple linear circuit that produces an output current (I X) that is a fraction of its input current (I T).
Figure 5. Schematic of Nyquist's 1928 thought experiment [6] [2] using two noisy resistors (each represented here by a noise-free resistor in series with a noise voltage source) connected via a long lossless transmission line of length . Each resistor's noise signal propagates across the line at velocity .
where resistance in ohms and capacitance in farads yields the time constant in seconds or the cutoff frequency in hertz (Hz). The cutoff frequency when expressed as an angular frequency ( ω c = 2 π f c ) {\displaystyle (\omega _{c}{=}2\pi f_{c})} is simply the reciprocal of the time constant.