Precious Metals Conductivity Table at Room Temprature

This table presents the electrical resistivity and electrical conductivity of several materials.

Electrical resistivity, represented by the Greek letter ρ (rho), is a measure of how strongly a material opposes the flow of electric current. The lower the resistivity, the more readily the material permits the flow of electric charge.

Electrical conductivity is the reciprocal quantity of resistivity. Conductivity is a measure of how well a material conducts an electric current. Electric conductivity may be represented by the Greek letter σ (sigma), κ (kappa), or γ (gamma).

Table of Resistivity and Conductivity at 20°C

Material ρ (Ω•m) at 20 °C
Resistivity
σ (S/m) at 20 °C
Conductivity
Silver 1.59×10−8 6.30×107
Copper 1.68×10−8 5.96×107
Annealed copper 1.72×10−8 5.80×107
Gold 2.44×10−8 4.10×107
Aluminum 2.82×10−8 3.5×107
Calcium 3.36×10−8 2.98×107
Tungsten 5.60×10−8 1.79×107
Zinc 5.90×10−8 1.69×107
Nickel 6.99×10−8 1.43×107
Lithium 9.28×10−8 1.08×107
Iron 1.0×10−7 1.00×107
Platinum 1.06×10−7 9.43×106
Tin 1.09×10−7 9.17×106
Carbon steel (1010) 1.43×10−7
Lead 2.2×10−7 4.55×106
Titanium 4.20×10−7 2.38×106
Grain oriented electrical steel 4.60×10−7 2.17×106
Manganin 4.82×10−7 2.07×106
Constantan 4.9×10−7 2.04×106
Stainless steel 6.9×10−7 1.45×106
Mercury 9.8×10−7 1.02×106
Nichrome 1.10×10−6 9.09×105
GaAs 5×10−7 to 10×10−3 5×10−8 to 103
Carbon (amorphous) 5×10−4 to 8×10−4 1.25 to 2×103
Carbon (graphite) 2.5×10−6 to 5.0×10−6 //basal plane
3.0×10−3 ⊥basal plane
2 to 3×105 //basal plane
3.3×102 ⊥basal plane
Carbon (diamond) 1×1012 ~10−13
Germanium 4.6×10−1 2.17
Sea water 2×10−1 4.8
Drinking water 2×101 to 2×103 5×10−4 to 5×10−2
Silicon 6.40×102 1.56×10−3
Wood (damp) 1×103 to 4 10−4 to 10-3
Deionized water 1.8×105 5.5×10−6
Glass 10×1010 to 10×1014 10−11 to 10−15
Hard rubber 1×1013 10−14
Wood (oven dry) 1×1014 to 16 10−16 to 10-14
Sulfur 1×1015 10−16
Air 1.3×1016 to 3.3×1016 3×10−15 to 8×10−15
Paraffin wax 1×1017 10−18
Fused quartz 7.5×1017 1.3×10−18
PET 10×1020 10−21
Teflon 10×1022 to 10×1024 10−25 to 10−23

Factors That Affect Electrical Conductivity

There are three main factors that affect the conductivity or resistivity of a material:

  1. Cross-Sectional Area: If the cross-section of a material is large, it can allow more current to pass through it. Similarly, a thin cross-section restricts current flow.
  2. Length of the Conductor: A short conductor allows current to flow at a higher rate than a long conductor. It’s a bit like trying to move a lot of people through a hallway.
  3. Temperature: Increasing temperature makes particles vibrate or move more. Increasing this movement (increasing temperature) decreases conductivity because the molecules are more likely to get in the way of current flow. At extremely low temperatures, some materials are superconductors.

 

Reference:
Ugur, Umran. “Resistivity of steel.” Elert, Glenn (ed), The Physics Factbook, 2006.

 

Hacking ECDSA based Digital Signature Algorithm

  • ECDSA is newer and is based on DSA. It has the same weaknesses as DSA, but it is generally thought to be more secure, even at smaller key sizes. It uses the NIST curves (P256).
  • RSA is well-regarded and supported everywhere. It is considered quite secure. Common key sizes go up to 4096 bits and as low as 1024. The key size is adjustable. You should choose RSA.
  • DSA is not in common use anymore, as poor randomness when generating a signature can leak the private key. In the past, it was guaranteed to work everywhere as per RFC 4251, but this is no longer the case. DSA has been standardized as being only 1024 bits (in FIPS 186-2, though FIPS 186-3 has increased that limit). OpenSSH 7.0 and newer actually disable this algorithm.
  • Ed25519, while not one you listed, is available on newer OpenSSH installations. It is similar to ECDSA but uses a superior curve, and it does not have the same weaknesses when weak RNGs are used as DSA/ECDSA. It is generally considered to be the strongest mathematically.

The video contains very nice example.

 

Reference guide for current carrying capacities for PVC twin and earth cables

Reference guide for current carrying capacities for PVC twin and earth cables

Reference Method

Description

1/1mm2
(A)

1.5/1mm2
(A)

2.5/1.5mm2
(A)

4/1.5mm2
(A)

6/2.5mm2
(A)

10/4mm2
(A)

16/6mm2
(A)

A

Enclosed in conduit in insulated wall

11.5

14.5

20

26

32

44

57

B

Enclosed in conduit or trunking on a wall

13

16.5

23

30

38

52

69

C

Clipped direct

16

20

27

37

47

64

85

100

Above plasterboard ceiling coved by insulation not exceeding 100mm thick

13

16

21

27

34

45

57

101

Above plasterboard ceiling coved by insulation exceeding 100mm thick

10.5

13

17

22

27

36

46

102

In stud wall in with insulation with cable touching inner wall

13

16

21

27

35

47

63

103

In stud wall in with insulation with cable not touching inner wall

8

19

13.5

17.5

23.5

32

42.5

 

Ratings shown are tabulated values from BS7671 Appendix 4 for 70°C PVC cables. Where appropriate, other rating factors must be applied.

Initial Magnetic Field Distribution Around High Rectangular Bus Bars Grigore A. Cividjian 1

SERBIAN JOURNAL OF ELECTRICAL ENGINEERING
Vol. 11, No. 4 (special issue), December 2014, 523-534

 

Abstract: The one-dimensional transient electromagnetic field in and around a
system of two nonmagnetic homogenous rectangular high thin bars can be
analytically evaluated if the ratio of average initial magnetic field on the two
sides of thin bar, or of the ratio of initial magnetic fields in middle of the bar
height is known. In this paper, using appropriate conformal mappings, an exact
analytical solution for these ratios are proposed in the case of very thin bars.
Obtained values are compared with FEM results for relatively thick bars.
Keywords: Conform mapping, Initial magnetic field, Elliptic integrals.
Introduction
The problem of transient electromagnetic fields for a system of two
infinite-high and long non-magnetic bars in cases of current and voltage step
application is completely studied and brilliantly solved in [1], considering the
magnetic field on internal side of the bars constant and evenly distributed and
on the external side of the bars equal to zero.

For more Please click the document to Download : Download PDF : 1-Cividjian