what happens to the resistance of most conductors as the temperature increases?
Discussion
introduction
Yech! What a mess this is.
Conduction: S. Grayness, 1729 — Resistance: Georg Simon Ohm, 1827.
Regular version…
I ∝V
| I = | V | ⇒ | V =IR | ⇒ | R = | V |
| R | I |
Variableogy…
- quantity: resistance R
unit: ohm [Ω] Georg Ohm (1787–1854) Federal republic of germany
Fancy version (the magnetohydrodynamic version?)…
J ∝Due east
Welcome to symbol hell…
| quantity | symbol | SI unit | symbol | belongings of… |
|---|---|---|---|---|
| resistance | R | ohm | Ω | objects |
| conductance | 1000 | siemens | S | |
| resistivity | ρ | ohm meter | Ωm | materials |
| conductivity | σ | siemens per meter | S/thou |
Ohm'due south law isn't a serious police. Information technology's the jaywalking of physics. Sensible materials and devices obey it, but there are plenty of rogues out there that don't.
resistors
Bad booze rots our young guts but vodka goes well.
Ameliorate build roof over your garage before van gets moisture.
| color | digit | multiplier | tolerance | tcr (10−6/K) | |
|---|---|---|---|---|---|
| none | ±20% | ||||
| pink | ten−3 | ||||
| silver | 10−2 | ±10% | |||
| gold | 10−ane | ±5% | |||
| black | 0 | 100+ | ±250 | ||
| brown | 1 | 101+ | ±1% | ±100 | |
| ruddy | 2 | x2+ | ±2% | ±50 | |
| orange | 3 | 103+ | ±0.05% | ±15 | |
| yellow | four | xiv+ | ±0.02% | ±25 | |
| green | 5 | ten5+ | ±0.50% | ±20 | |
| blueish | 6 | ten6+ | ±0.25% | ±x | |
| violet | 7 | ±0.10% | ±5 | ||
| gray | 8 | ±0.01% | ±1 | ||
| white | ix | ||||
materials
Resistance and resistivity. Factors affecting resistance in a conducting wire.
Conductors vs. insulators
Best electrical conductors: silver, copper, gold, aluminum, calcium, glucinium, tungsten
Resistivity and conductivity are reciprocals.
Conductivity in metals is a statistical/thermodynamic quantity.
Resistivity is determined by the scattering of electrons. The more scattering, the higher the resistance.
where…
| σ = | conductivity [S/yard] |
| n = | density of free electrons [due east/m3] |
| e = | accuse of an electron (ane.60 × 10−19 C) |
| me = | mass of an electron (ix.11 × 10−31 kg) |
| vrms = | root-mean-square speed of electrons [one thousand/south] |
| ℓ = | hateful free path length [m] |
Graphite
Where does this idea belong? Nichrome was invented in 1906, which made electric toasters possible.
Conducting polymers.
Resistivity of selected materials (~300 K)
(Notation the difference in units betwixt metals and nonmetals.)
| metals | ρ (nΩ m) |
|---|---|
| aluminum | 26.5 |
| brass | 64 |
| chromium | 126 |
| copper | 17.one |
| gilt | 22.i |
| fe | 96.1 |
| lead | 208 |
| lithium | 92.viii |
| mercury (0 °C) | 941 |
| manganese | 1440 |
| nichrome | 1500 |
| nickel | 69.three |
| palladium | 105.4 |
| platinum | 105 |
| plutonium | 1414 |
| silver | xv.9 |
| solder | 150 |
| steel, evidently | 180 |
| steel, stainless | 720 |
| tantalum | 131 |
| tin (0 °C) | 115 |
| titanium (0 °C) | 390 |
| tungsten | 52.viii |
| uranium (0 °C) | 280 |
| zinc | 59 |
| nonmetals | ρ (Ω m) |
|---|---|
| aluminum oxide (14 °C) | 1 × x14 |
| aluminum oxide (300 °C) | 3 × ten11 |
| aluminum oxide (800 °C) | 4 × 106 |
| carbon, baggy | 0.35 |
| carbon, diamond | 2.7 |
| carbon, graphite | 650 × 10−9 |
| indium tin oxide, thin film | 2000 × 10−9 |
| germanium | 0.46 |
| pyrex 7740 | twoscore,000 |
| quartz | 75 × 10xvi |
| silicon | 640 |
| silicon dioxide (20 °C) | ane × 1013 |
| silicon dioxide (600 °C) | 70,000 |
| silicon dioxide (1300 °C) | 0.004 |
| water, liquid (0 °C) | 861,900 |
| h2o, liquid (25 °C) | 181,800 |
| h2o, liquid (100 °C) | 12,740 |
temperature
The general rule is resistivity increases with increasing temperature in conductors and decreases with increasing temperature in insulators. Unfortunately in that location is no simple mathematical part to draw these relationships.
The temperature dependence of resistivity (or its reciprocal, conductivity) tin just be understood with quantum mechanics. In the same mode that thing is an assembly of microscopic particles called atoms and a axle of light is a stream of microscopic particles called photons, thermal vibrations in a solid are a swarm of microscopic particles called phonons. The electrons are trying to drift toward the positive terminal of the battery, but the phonons keep crashing into them. The random direction of these collisions disturbs the attempted organized motion of the electrons confronting the electric field. The deflection or scattering of electrons with phonons is ane source of resistance. As temperature rises, the number of phonons increases and with it the likelihood that the electrons and phonons will collide. Thus when temperature goes upwardly, resistance goes up.
For some materials, resistivity is a linear function of temperature.
ρ = ρ0(1 + α(T −T 0))
The resistivity of a conductor increases with temperature. In the case of copper, the relationship betwixt resistivity and temperature is approximately linear over a broad range of temperatures.
For other materials, a power relationship works better.
ρ = ρ0(T/T 0)μ
The resistivity of a conductor increases with temperature. In the case of tungsten, the relationship between resistivity and temperature is best described by a power human relationship.
see as well: superconductivity
miscellaneous
magnetoresistance
photoconductivity
liquids
electrolytes
gases
dielectric breakup
plasmas
microphones
A carbon microphone is a backward zilch
| type | sounds produce changes in… | which cause changes in… | which consequence in changes in… |
|---|---|---|---|
| carbon | granule density | resistance | voltage |
| condenser | plate separation | capacitance | voltage |
| dynamic | coil location | flux | voltage |
| piezoelectric | compression | polarization | voltage |
Source: https://physics.info/electric-resistance/
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