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).

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.

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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.

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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.