The temperature coefficient of resistance of copper - NIST Page

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John A. Roebling's Sons Company, Trenton, N. J. Standard Underground Cable Company, Perth. Amboy, N. J. Heddernheimer. Kupferwerk und Suddeutsche.
THE TEMPERATURE COEFFICIENT OF RESISTANCE OF COPPER By

H. Dellinger

J.

CONTENTS Page I.

II.

Introduction

Former Values

Use

72

2.

Necessity for the Present Investigation

73

in

Experimental Data

73

74

3.

The Resistance Measurements The Temperature Coefficient Measurements The Sources of Material Represented

4.

Effect of Chemical Differences of Samples

78

5.

Effect of Physical Differences of Samples

6.

Hardening Copper Samples that had never been Melted

79 80

1.

2.

7.

III.

72

1

74 77

Effect of Local

81

Conclusions

83

1.

Proportionality of Temperature Coefficient and Conductivity

83

2.

The Resistivity-Temperature Constant

84

3.

Temperature Standard

Correction

Measurements

against

a

Copper 84

Hardening, Impurities, and Distortion on the Tem-

4.

Effect

5.

The Temperature

of

for

perature Coefficient

Measurement

of Conductivity".

,

.

Odd Shapes

b.

c.

86

Short Samples Wires that have been Distorted and Bent d. The Estimation of Chemical Purity Explanation of Disagreements of Previous Observers

87

Values Suggested for Annealed and Hard-Drawn Copper IV. The Mathematical Expression of the Temperature Coefficient 1. On General Functions of Temperature 2. Calculation of Linear Temperature Coefficient from Observations. 3. Effect of Thermal Expansion in the Expression of the Linear 7.

.

Temperature V. Summary VI. Appendix.

85 86

86 86

a.

6.

Coefficient as a

Coefficient

—Reichsanstalt

87 88

88 88 92 93 96

Results

97 71

Bulletin of the

72

Bureau

of

Standards

[Vol. 7,

No. I

INTRODUCTION FORMER VALUES IN USE I.

1.

temperature coefficient Some of those which have been much

Widely varying values are of resistance of copper.

in use for the

used are given in the following table, in which aQ and respectively by the equations:

^^20

are given

= Ro (i+^oO Rt -R20 (i+«'2o[^-2o]) i^< = resistance respectively at 0° C, at 20° C, and Rt

Rq,

i?20J

t = any temperature

at t°.

centigrade ^0

^20

0.00398

0.00369

Laboratoire Central d'Electricite

.00400

.00370

Kennelly and Fessenden, 1890

.00406

.00375

.00420

.00387

Verband Deutscher Elektrotechniker

.00426

.00392

(British) Institution of Electrical Engineers

.00428

.00394

Lagarde, 1893

.00445

.00409

Matthiessen's temperature coeflBcient,

American

0° C

to

20°

C

Institute of Electrical Engineers

Matthiessen's formula is: X«==Xo (i— 0.0038701 /+0.000009009 conductivity, or reciprocal of resistance, at t° and 0° C, respectively.

t"^).

X


and one other temperature, t. The "differential at^'' is the temperature coefficient obtained when a copper sample is measured against another in the same bath and thus undergoing the same variations of temperature. It is simply the difference of the temperature coeffi*^

Differential

«'