What is Resistivity: Definition and 199 Discussions

Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. Its inverse, called electrical conductivity, quantifies how well a material conducts electricity. A low resistivity indicates a material that readily allows electric current. Resistivity is commonly represented by the Greek letter ρ (rho). The SI unit of electrical resistivity is the ohm-meter (Ω⋅m). For example, if a 1 m 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.
Electrical conductivity or specific conductance is the reciprocal of electrical resistivity. It represents a material's ability to conduct electric current. It is commonly signified by the Greek letter σ (sigma), but κ (kappa) (especially in electrical engineering) and γ (gamma) are sometimes used. The SI unit of electrical conductivity is siemens per metre (S/m).

View More On Wikipedia.org
Recent contents Top users
  1. minimario

    Temperature Variance with Resistivity

    Homework Statement ti[/B] A resistance thermometer, which measures temperature by measuring the change in resistance of a conductor, is made of platinum and has a resistance of 50.0 Ohms? at 20.0°C. (a) When the device is immersed in a vessel containing melting indium, its resistance increases...
  2. jawad hussain

    Why do resistivity and conductivity change with temperature?

    why resistivity of a metal increases with increase of temperature and conductivity of a semiconductor increases with increase in temperature??
  3. chikou24i

    Understanding Limit Current & Resistivity in Source Meter Machines

    We see always in source meter machines a LED which indicates the limit current. I want to know what is the limit current and what is the relationship between this later and the resistivity.
  4. S

    (Solid State) low resistivity dependance on temperature

    Homework Statement For some applications it is important to minimize the temperature dependence of electronic components. For example, there is a special alloy called constantan that can be used for temperature independent resistance elements. Do you expect constantan to have a high or low...
  5. S

    Resistivity mean free path and scattering time of copper

    so this is the question I'm having a little trouble with: Assume that the ratio of copper resistivity at room and absolute zero temperatures (so called "residual resistance ratio") is 1000. Estimate the electron mean free path in copper at low temperatures. we also know this: Let us assume...
  6. M

    Charge flowing through/across a Capacitor?

    Homework Statement Dry air has a resistivity of about 3*10^13 Ωm. A capacitor has square plates 10cm on a side separated by 1.2mm of dry air. The capacitor is charged to 250V. Assuming the potential difference does not change as the charge flows, what fraction of the charge will flow across the...
  7. 1

    Estimating Resistivity of Amorphous Metal - Condensed Matter

    Homework Statement Estimate the resistivity of an amorphous metal whose mean free path is of the order of an atomic spacing. Compare your answer to crystalline copper.Homework Equations VF = h(bar) KF / m VF = l / τ ρ = m / n e2 τ The Attempt at a Solution I think my real issue with this...
  8. S

    How can powder resistivity be measured with 4-point probe?

    I am studying on Fe powder samples. I have used I-V measurement system to get resistivty. However, I would like to measure with 4-point probe. but I am confused how to prepare the powder sample for 4-point probe. could you tell me there is a way?
  9. marcophys

    HT 'low current' resistance fundamentals in Tungsten Welder - event horizon

    Does anybody understand the fundamentals of what is happening in this circuit? Tungsten welding info is all about high current... but this is a low current scenario. AC input, CDI Coil generated 20Kv (estimated) suffers voltage drop over 100mm of tungsten rod. The larger the diameter... the...
  10. J

    Why Is Length Divided by Area in the Resistivity Formula R=P*(L/A)?

    Hello, I am curious why in the resistivity formula you divide the length by the area? R=P*(L/A). I cannot figure why you would not take the L*A to get volume?
  11. Greg Bernhardt

    What is Resistivity? Definition & Equations

    Definition/Summary For a given material, the resistance of a length of the material is a constant times its length, and divided by its cross-section area. This constant is the resistivity, \rho, of the material. Resistivity of a material is measured in ohm-metres (\Omega m), or...
  12. S

    Regarding resistivity in heating coils

    I have a question regarding "ohm level" in a heating element in the design of a device designed to vaporize a liquid. I thought I had a pretty solid understanding of this but I've been told that I was wrong. So, I thought that if you increase the resistance (higher ohm) in a heating...
  13. V

    Resistivity anti-helmholtz configuration

    If I have a pair of coils connected in an anti-helmholtz configuration, with current flowing oppositely in both, and I wanted to calculate the resistivity- wouldn't the length of both coils just be summed up? I tried this but I am not getting the answer I want.
  14. O

    NiCu Alloy Resistivity - Is it 3.5*10^8 or 35*10^8 Ω*m?

    I am very sorry because this post seems spammy, but I cannot, for the life of me, find the resistivity of NiCu alloy. My lab has it as 35*10^8 Ω*m, and when i compare my calculated value of resistance to the theoretical it is off by a factor of 10. This causes me to think that there is a...
  15. L

    Calculating Resistivity of Doped Si: P and As Substrate Comparison"

    How do I calculate the resistivity of a doped Si if I have to substrate of the same type. Let's say a P and As doped Si. Is the mobility given by, \mu_n(N_d + N_d), or should I do this in an other way? Further, when I calculate the resistivity, is the concentration, N_{tot} = N_d(P)+N_d(As) ...
  16. B

    Solving Resistivity Question: Determine Shunt Length

    Homework Statement Determine the length of the shunt if the c.s.a of the copper is 25cm^2. Homework Equations R = ρ l/a Resistance of shunt is 0.5μΩ The Attempt at a Solution Transposing to find l. l = AR/ρ =25^2x10^2 x 0.5x10-6/1.7x10-8 =7.4mm is the length of the shunt...
  17. F

    What is the resistivity of a copper wire with given dimensions and length?

    Homework Statement A number 12 copper wire has a diameter of 2.053mm. Calculate the resistance of a 31m long piece of such wire. Use rho=1.72x10-8 Ohm-m for the resistivity of copper. Homework Equations This is the part that I am unsure of, all of my equations for resistivity do not...
  18. E

    Calculate resistivity of a wire

    Hello All, I was curious to know if there is a way to calculate resistivity of a wire that did not have a uniform cross section? For example, what if the cable was in a bow-tie geometry? Is there anyway to quantify the electrical resistivity of the constriction (the area of the cable that has...
  19. J

    Calculating Resistivity and Resistance: Solving for Unknowns

    Homework Statement Homework Equations R=pL/A The Attempt at a Solution The answer is C and I don't know why. If R = pL/A then isn't L=b between X and Y?
  20. J

    Electrical resistivity tomography

    Hi all, I have been searching the internet for explanations on the method of ERT, but they are in general extremely complex and contain very specific vocab that I'm not understanding. Would somebody care to explain to me the method of ERT in language that an A Level student can understand...
  21. J

    Resistivity in Archaeology: A Tool for Identifying Underground Objects?

    Hi all, I am writing an assignment at the moment, asking me to report on the use of resistivity in identifying objects under the ground. I've gotten confused as to whether resistivity is used at all - surely resistance is all that is needed? For example, in any multi probe resistive survey, the...
  22. F

    Resistivity of a material involving temp

    Homework Statement A) To= 35 °C find α And β B) determine the temp in which this material becomes a super conductor as predicted by the equation below. ρ=ρ0(1 + α(T-To) + β(T-To)^2)To= 35 C. ρo=2.5e-8Ω m T1= 0 C. ρ1=2.346e-8Ω m T2= 100 C. ρ2=3.036e-8Ω mHomework Equations ρ=ρ0(1 +...
  23. B

    Units of Resistivity Explained

    Hello, In my lab report, I am trying to discuss what the units of resistivity mean. For instance, the unit of speed m/s second can be described as the time it takes to travel 1 m; specifically, 50 m/s would say that it would take 1 s to travel 50 m, or, we travel 50 m every second. Could...
  24. A

    Temperature dependence of the electrical resistivity of a metal

    the electrical resistivity ρ of a metal is proportional to the probability that an electron is seattered by the vibrating atoms in the lattice an this probability is in turn proportional to the mean square amplitude of vibration of these atoms.How dose the electrical resistivity ρ of the metal...
  25. B

    Resistivity measurements of a circular shaped sample

    Hai, I am doing my masters degree in physics. can somebody help me in which formula to use for calculating resistivity of a sample of circular shape using two probe measurements, which should include thickness and correction factor also. Thank You!
  26. H

    Resistivity of a current in a fluid

    I am studying the resistivity of various materials in my physics class and I have a query regarding conductive fluids. If a current is running through a fluid (let's say water) within a rectangular beaker, and there are two copper wires put in at opposite ends of a beaker (I believe they are...
  27. P

    Temperature Coefficient of Resistivity

    Hi I was wondering if anyone could help. My teacher isn't very good at explaining things and he's given us a question without going through the reasoning behind the equation. Aluminium wire has a resistance of .250Ω at 0°C. Give that the temperature coefficient of resistivity at 0°C for...
  28. V

    Zero resistivity in superconducting state

    Hi everyone, - Could you explain for me the meaning of "net" in the phrase "small net attraction between electrons" in superconductivity, (or synonym of it)? - We usually say that BSC theory explains the superconductivity of conventional superconductors, one feature of superconductivity is...
  29. J

    Environmental Resistivity Study in Landfill Showing Lack of Signal Detection

    Hello All, I am a graduate student conducting a shallow subsurface geophysics study over closed landfill cells and have run into a bit of a problem with my data collection. I have ran traverses spaced 10 m apart running E to W across cells with all traverse lines ran twice using two...
  30. V

    Resistivity and Ohm's Law question

    Homework Statement A long wire connected to the terminals of a 12V battery has 6.4 x 1019 electrons passing a cross section of wire each second. calculate it's resistance. answer is 1.2ΩHomework Equations q = ne q = IE R=ρ L/AThe Attempt at a Solution V= 12v n= 6.4 x 1019 electrons R=? First...
  31. N

    Resistivity of conducting putty?

    I'm trying to find the resistivity of conducting putty at room temperature and I've been looking all over google with no success. There isn't really anything more I can do to work it out so I'm wondering if anyone here knows. Thanks :)
  32. harts

    Calculate Resistivity of a Rod

    Homework Statement A uniform metallic rod, with a cross-sectional area of 1.83 cm2 and a length of 7.08 m, contains 6.24E28 conduction electrons per cubic meter of material, which have a mean collision time of 20.2 femtoseconds. (a) Determine the resistivity of the rod. When the rod...
  33. J

    How to calculate resistivity of coaxial cylinder

    Is it any model on resisivity of two tightly-attached coaxial cylinder? For example, a copper core wire is coated with layer of aluminum. How to calculate the final resistivity along axis?
  34. L

    Relationship between resistivity and Mathiessen's Rule

    This question has bogged me down for hours. Please help. An alloy of metals is found to have a resistivity of 1.2e-6Ωm at 300K. When it is heated to a temperature of 973K, the resistivity is found to increase by 10 per cent. Assuming Mathiessen's rule to hold good for the alloy, find its...
  35. V

    Electron-hole pair damping of vibration, thin film resistivity

    Hello, I'm reading something about adsorbate induced surface resistivity changes in thin metal films and there is often mentioning of electron-hole pair damping, as for example: "electron-hole pair damping of the parallel(to the surface of thin film) frustrated vibration of the...
  36. E

    Question involving resistivity using the formula?

    Homework Statement The resistivity of nichrome wire is 1.1micro ohm meters. What length of wire of diameter 0.079 mm is required to provide resistance of 1.0 Kohm? Homework Equations R=resistivity x length/area The Attempt at a Solution 1000ohms = ? x 0.0011/0.079 79 = ? x...
  37. A

    Resistivity of Nichrome experiment

    Every year we do an experiment to find the resistivity of Nichrome wire, and every year the result is the same: 5 x 10^-7 instead of 1 x 10^-6. For the life of me I haven't been able to track down why it's a factor of 2 off. We use a Wheatstone bridge that has a 1 m length Nichrome wire...
  38. S

    How Does Resistivity Affect Copper Wire Resistance and Current Flow?

    12-gauge copper wire has a radius of 1.03×10−3 m. (a) What is the resistance of 11.5 m of this wire at 20°C. (b) How much current will pass through the wire if a potential difference of 9.00 V is applied across it? The resistivity for copper is 1.7E-8 ohm meters For part a: The equation is...
  39. K

    Bloch Theory of electrical resistivity - Derivation

    In "Electrons and Phonons" by Ziman which you can find here, I have a problem with equation (9.5.14) on page 360 and (9.5.17) on page 361. I don't understand how from the first equation where you have double surface integral you obtain the second equation with only one integral over q. I...
  40. K

    What does negative resistivity mean

    silicon has a negative temperature coefficient of resistivity. So that means that it's resistivity decreases as temperature increases. How is that possible? Also, would that mean that at some certain temperature higher than room temp, silicon would act as superconductor? It has a very high...
  41. Z

    Sources for resistivity of W depending on temperature

    Hello everyone I am trying to do an experiment involving a W bulb, in which I am completely dependent of knowing the temperature-resistivity relation of Tungsten in the temperature range 300 - 2500 K. The CRC handbook has some tables, but they have few data points and correlate poorly with...
  42. J

    A conducting wire has a resistivity

    Homework Statement A conducting wire has a resistivity, ρ as a function of its length, L, given by ρ=(ρ0)(L) where (ρ0) is constant. A is the cross-sectional area of the wire. the resistance of the wire would be A) [(ρ0)(L)]/A B) (ρ0)/(2A) C) [(ρ0)(L)]/(2A) D) [2(ρ0)(L^2)]/A E)...
  43. P

    How does the molecular bonding effect the resistivity of a material?

    Hello all, I want to understand the molecular structure for different electronic components: Conductors - need to have metallic bonding, where electrons are free to move about Dielectrics - are insulators, but ideally atoms need to be polarizable, without charge actually being able to...
  44. L

    Internal resistivity, is this right?

    Homework Statement To a source of current, one by one are added 2 resistances, first R1=1ohm, then R2=4ohm. In both cases, in the same period of time (t=t1=t2), the resistors give the same amount of heat (Q=Q1=Q2). Determine the internal resistance ("r" small r) of the electric source...
  45. E

    Measuring Resistivity in a sample of A356

    I'm trying to measure the resistivity of a sample of A356 to back out the thermal conductivity. I do not have anything sensitive enough to measure the micro-ohm resistance (my sample is 0.5" x 0.25" x 3"). If I want to use an oscilloscope or multimeter to measure the voltage drop, I should...
  46. P

    Computation of resistance with arbitrary local resistivity rho(x,y,z)

    Bonjour, I need to numerically compute the net electrical resistance of a given geometry. I know the shape of my object, it is relatively simple. It's close to this: http://2.imimg.com/data2/QX/UC/IMFCP-3019296/i-shape-big-1-250x250.jpg Actually my shape is even simpler because it's a...
  47. I

    The Effect of Temperature on Resistivity

    1) A thermistor is connected through a switch to a 12V power supply of negligible internal resistance. When the switch is closed, the initial current in the circuiy is 14mA. A few minutes later it has risen to a constant 20mA. Does the thermistor dissipate more power initially, or after it...
  48. I

    Help Easy Physics - Resistivity Ratios

    The resistivity of Aluminium is twice that of copper. However, the density of Aluminium is one-third that of Copper. a) For equal length and resistance, calculate the ratio: mass of aluminium/mass of copperI'm thinking, the density ratio (Al:Cu) is 1:3 ...and the resistivity ratio is 2:1 ...so...
  49. I

    Help with a current, resistance, and resistivity problem

    Homework Statement In the figure below, current is set up through a truncated right circular cone of resistivity 898 Ω·m, left radius a = 2.00 mm, right radius b = 2.30 mm, and length L = 1.64 cm. Assume that the current density is uniform across any cross section taken perpendicular to the...
  50. A

    Electric plate has three sections with equal resistivity

    Electric plate has three sections with equal resistivity. Those resistivities combined parallel - water boils per 6 minutes. How much time it will take to boil the same weight and same initial temperature of the water if we will combine resistivities sections like in A and C Thanks very much
Back
Top