# What is Resistivity: Definition and 198 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).

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1. ### Measured Surface Resistivity Much Higher than Theoretical Value (Why?)

I recently conducted a physics lab to measure the surface resistivity of a conductive sheet of a paper with a carbon filler. The theoretical Rs is approx. 5,000 Ω/☐ for this paper and yet we have calculated two Rs values: Rs when Varying Length and holding Width = 10100 +/- 83.07 Ω/☐ Rs when...
2. ### I Why is resistivity inversely proportional to resistance for NTC semiconductors?

Why is resistivity inversely proportional to resistance for NTC semiconductors?
3. ### Resistance of a half ring of a given resistivity

Lets suppose a half ring whit internal radius a and external radius b and height t. We can calculate the resistance of the half ring considering that it is made of a number of parallel resistors each one with resistance given by: R = ρ L/S where L = π·r and S = t·dr. The resistance of each...
4. ### What is the resistivity of a wire when voltage increases?

Divide volts by current to get resistance which is 8. Multiply both sides by 8 and sigma to get: $$\frac{1m}{8\Omega\times10^{-4}m^2} = 1250$$ But this answer seems to be way off. How did I go wrong? Thanks
5. ### I Question regarding Electrical Resistivity of metal vapors

What is the electrical resistivity of Caesium vapor? What is the electrical resistivity of Potassium vapor? Sorry there are no support material or reference links for this. Just a question. The unit must be in Ohm-meter.
6. ### I Resistivity of a conductor

I read that resistivity is related to the mean free path of electrons inside the material and on density of charged within it. The electric field does work to flow electrons through a resistor, and the energy is converted into heat due to collision with lattice ion, right? ( in free space they...
7. ### Finding a radius of a wire

i really have tried all the formulas out there and can't seem to get a solid answer
8. ### Can two variables in two different equations cancel each other?

Using the related equations, I have come up with an equation that I think would answer this question (#4). However, I was just wondering does the 'L' from equation #1 and 'l' in equation #3 cancels each other out when the substitution is made to give out equation #4 (since they are both the...
9. ### Please check my calculation of the resistance of this wire shape

I explained what I want to tell you in the picture I add. Thanks in advance.
10. ### Resistivity equation relating to equations for resistors

1. Would k be p/π? (since resistivity of a material is a constant property and π is a constant) I understand that typically R = pL/A Therefore, would the equation be R = k(x/(d/2^2)) Confessedly, I truly am baffled. 2. R total = sum of individual resistors (in series) R total = R1 +...
11. ### Determining the resistivity of intrinsic Germanium

Hi. Since, I can find conductivity by taking the reciprocal of resistivity, in this case, 1/0.455 Hence, I will end up with: ##\frac{1}{0.455}=C(300)^{-3/2}e^{(\frac{-0.67}{2(1.38*10^{-23})(300)})}## However, my C value seems to be invalid in this case. May I know what may went wrong here? Thanks
12. ### I Mobility and resistivity as a function of temperature

Referencing: http://www.vlsiinterviewquestions.org/2012/07/21/inverted-temperature-dependence/ Mobility decreases in a MOSFET with increasing temperature However, referencing: https://www.quora.com/Why-does-resistivity-of-semiconductors-decrease-with-increase-in-temperature Resistivity...
13. ### Resistivity and wire length

L=Ra/P =6x0.0006/5x10^-8 =72000
14. ### Electric resistivity and friction

In the situation of a magnet moving towards a flat sheet of copper; why doesn't the copper gain angular moment as the electrons move in concetric circles? The electrons are experiencing friction as they move through the copper.
15. ### I Fuchs-Sondheimer Resistivity model for Nanowires

I calculated FS Model using Mathcad and I got that this part increases with decreasing width $\w$. This make the resistivity increases with decreasing width $\w$. This contradict the result of this model. Has anyone ever come across with this before? the original paper...
16. ### A Why do we need to know "two-bands" Hall coefficient and magn

(Oh my god, why can't my post show normally? Some sentences just disappear, but I can still see them while editing. It's very weird. Can someone help me? I've reported.) I know only partially filled bands result in current density, and I think there must be not only 2 partially filled bands...
17. ### Find the resistivity of the resistive wire

Homework Statement Homework Equations ##ρ=\frac{RA}{L}## ##I=\frac{ΔQ}{Δt}## ##I=\frac{ΔV}{R}## The Attempt at a Solution (a) ##ρ=\frac{RA}{L}## ##L=\frac{2*π*r}{2} = πr## ρ = (5*2.5*10-7)/(π*0.1) ρ = 4*10-6 Ωm. (b) Req = 7+5 = 12Ω ##I=\frac{ΔV}{R}## I = 36/12 = 3 A ##I=\frac{ΔQ}{Δt}## 3 =...
18. ### How did H.K. Onnes measure temperature and resistivity?

How did H.K.Onnes measure temperature and resistivity? As you know, Onnes is a dutch physicist that was the first person to liquefy helium and discover superconductivity a year or so later. I am wondering - what equipment was he using at that time? I couldn't find this information anywhere...
19. ### A AC transport data query (using a PPMS system)

Hello and thanks for looking at this question. I have a semi-conducting sample which has been run on a PPMS system - measuring it's resistivity as a function of temperature. I switched to AC transport mode in order to measure the resistivity again while applying frequencies between 1Hz -...
20. ### Highly collisional yet low resistivity plasmas

In approximations for the applicability of ideal MHD to plasmas, it states that plasmas are considered highly collisional to permit the assumption that the plasma (i.e. electrons) follow a Maxwellian velocity distribution. Although is not resistivity based on collisions in the plasma? If there...
21. S

### Why is Sn a better conductor than Pb?

Homework Statement Hi guys, I'm currently writing an extended essay in Physics looking at the effect of percentage composition of Sn has on the electrical resistivity of SnPb Solder. I've noticed that Sn is listed as being a better conductor than Pb, despite trends of periodicity and have been...
22. ### Resistance of 2 materials, different resistivity, combined

Homework Statement A 60-cm long gold wire is soldered to a silver wire of the same length as shown in the diagram. If each wire is 2.00 mm in diameter, determine the equivalent resistance of the combination between A and B. Diagram is attached. Homework Equations R = ρL/A The Attempt at a...
23. ### Resistivity of a wire that is wound close on a cylinder

Homework Statement Homework Equations R= pl/A effective resistance= 1/R The Attempt at a Solution I'm honestly don't know where to start, althought I know i need to do something with the 200 coils first, but I have no idea what should be done with it
24. ### I Longitudinal resistivity in Integer Quantum Hall Effect

I have studied the integer quantum hall effect mainly from David Tong's notes and i understand how the ## \rho_{xy}## is quantized in terms of the chern number. What I don't understand is - how the chern numbers relate to the number of filled Landau levels though. - I also don't understand the...
25. ### Estimation of material loss through electrical resistivity

Hi all, I'm doing a little project about the wear of materials for tools for cutting machines.Yesterday, I was reading wikipedia page about electrical resistivity and I thought if it might be possible to evaluate the estimate the material loss of the tool through the measure of electrical...
26. ### Lab: Plot graph of resistance, R (in Ohms) versus 1/d^2

Homework Statement We were given five samples of nichrome wire, each with a different diameter but the same length. A micrometer was used to measure the diameters. We then measured and recorded the electrical resistance, R in Ohms of each nichrome sample with a DMM. I will try to summarize all...
27. ### Electric field in a wire with same current as another wire

Homework Statement For what electric field strength would the current in a 2.0-mm-diameter nichrome wire be the same as the current in a 1.0-mm-diameter gold wire in which the electric field strength is 0.0095 N/C? dn = .002m dg = .001m Eg = .0095 N/C ρn = 100 * 10-8 Ωm ρg = 2.44 * 10-8 Ωm...
28. ### Resistance of a Wire at varying temperatures

Homework Statement Determine the resistance of wire at room temperature and at the melting point of the given material. GIVEN: Material = Aluminum Diameter of wire ##= 0.5 mm = 5.0 * 10^{-4} m## Length of wire ## = 0.5 m = 5.0 * 10^{-1} m## Temperature Coefficient: ##\alpha = 3.9 *...
29. ### Resistivity and Temperature

Homework Statement Initially, copper wire is 20oC then raises the temperature of the wire casing the resistivity up 12%, find the temperature at the final. Homework Equations R=Rref[1+α(T-Tref)] The Attempt at a Solution I am completely confused with this mathematics problem,Stucking with...
30. ### Maximum current carrying capacity (theoretically infinite?)

I started simply looking at a circuit breaker connection diagram, then I fell down the rabbit hole. So I wondered, if you had a piece of pure copper and getting rid of heat (structural integrity, gravity etc.) was not an issue, just how much current could you push through it before it hit it's...
31. ### I What affects resistivity?

I am depositing VO2 thin films on quartz and aluminum substrates and I need to find out whether the choice of substrate can effect the resistivity of the VO2 film. I know resistivity is a function of temperature but am not sure if it is effected by substrate choice. Any thoughts?
32. ### B Resistivity tensor and Magnetoresistance

Hey everyone, I'm currently trying to understand the resistivity and conductivity tensor of a 2D sample. If a current carrying metal bar is placed inside a magnetic field the Hall Effect comes into play. I tried to search for explanations on how to obtain the resistivity tensor of the metal bar...
33. ### Resistivity of graphite sheets?

I'm trying to calculate the possible resistance of a graphite sheet that I'm using to coat surfaces of metal conductors, protecting them from wear, welding, and other possible failures. I can't seem to find an accurate value for the Resistivity, some sites state it's 7.8E-06, while others 3 to...
34. ### A Computing the resistivity due to electron collision with 1BZ

Hello there, Id like to estimate how the resistivity due to electron 'collision' with 1st Brillouin zone changes as a function of number of valence electrons in a metal. Say you start with Na, then add some other material with 2 valence electrons instead of 1, then the fermi wavevector will...
35. ### B Resistivity of pencils

forgive me if this is too chemistry. I am playing around with pencils, writing and art pencils, to teach some kids about resistance and resistivity in a fun way, or so I believe. I get about 200 Ohms for a standard full length HB (whatever that means) pencil. I have some charcoal art pencils...
36. ### Looking for resistivity vs. temperature lab charts

Hi everyone, I am looking for basic elements resistivity vs. temperature laboratory measurements charts. Anyone has ideas where to look for? Regards
37. ### Calculate Resistance and resistivity

I have voltage, diameter, area, and inverse area data values. How could I calculate the resistance and resistivity with these numbers? I am pretty sure resistance is R=V/I and resistivity= RA/L , so I am not sure how I can calculate resistance without an I value.
38. ### Finding temperature coefficient of resistivity of the alloy

Suppose a wire made from an unknown alloy and having a temperature of 20.0°C carries a current of 0.529 A. At 52.4°C the current is 0.378 A for the same potential difference. Find the temperature coefficient of resistivity of the alloy. tempinital = 20C tempfinal = 52.4C currentInital = .529A...
39. ### Calculating Resistivity across a mesh sheet

Hi everyone! I'm trying to figure out how to go about this in calculating resistivity of a titanium grade 1 mesh. From what I know the ρ for titanium is 4.3x10^-8 ohm x m. The mesh will be a 1x12inch sheet wrapped cylindrically end to end. Here are the stock values including a change in area...
40. ### Theoretical vs measured sheet resistance of conductivity paper

Homework Statement After performing a lab experiment to determine the conductivity if Pasco conductivity paper, I found the conductivity to be 0.195 Ωm. We found conductivity by graphing measured values of voltage (y axis) and the length (x axis) between the probes of a voltmeter that are...
41. ### How dopant enhances the superconductivity of BSCCO

Good day! i really need your help, I want to know the effect of Dopant (for Example Manganese) in BSCCO (for example Bi-2212) on it's Resistivity? i read some articles saying it increases the critical temperature of the superconductor, But it didn't explain why, and how is that related to the...
42. ### Electrical conductivity of seawater depends on salinity how?

Hi! I am currently trying to determine how the salinity ##S## of a sample of seawater (or, objectively, a salt-water solution) changes its electrical conductivity ##\sigma##. It is clear that they are proportional since the mobility of the ##\text{Na}^{+}## and ##\text{Cl}^{-}## ions plays a...
43. ### Divergence of electric field

Why is the divergence of electric field not zero for a material with non-constant conductivity?
44. ### Need help in determining a source of error in an experiment

Homework Statement It is known that the theoretical resistivity of copper is approximately: 2*10^-8 Ωm. But after I conducted an experiment to find the resistivity of copper, the results turned out to be: 1.68*10^-8Ωm. This is a very small error that can be easily dismissed due to "human...
45. ### How does corrosion affect the resistivity of copper wire?

I'm not sure if corrosion does have a significant effect on copper in general but if it does, how and why does it happen, and the process of it happening and its effect on the overall resistivity? This is for a physics assignment...Please help if you can. Thank you
46. ### Quantum Hall Effect resistivity

I'm having trouble understanding why the resistivity behaves as it does in comparison to the density of states for the quantum hall effect. Take the following two diagrams: (A) (B) I understand that there can be no scattering in (A) because all states are full (i.e. no elastic) and the gap is...
47. ### Are density and resistivity proportional?

Today while reading a book i read that conductance of a metal depends on its density. But it is also dependent on its resistivity. Does that mean that resistivity and conductivity are proportional to each other?
48. ### Resistivity of two copper wires using valence shell information

Homework Statement Homework Equations Please see below. The Attempt at a Solution From my thread in the Solid State section (and input from DrDu): The Thomas-Fermi wavevector relates to the damping of an electric field caused by build up of carriers around an impurity (screening). Where...
49. ### Length of Wire Effect on Current and Inner Electric Field.

>Two wires of the same material are both connected to a 9-V ideal battery. They have the same cross section area but wire 2 is twice longer than wire 1. Compare the following quantities by answering if the quantity for wire 1 is smaller, equal or greater than the same quantity in wire 2. > -...
50. ### 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...