Experiment (5): conduction on solid materials (temperature dependence of noble metal Resistor )

Solid state Lab PHYS 485 King Abdulaziz University

Experiment (5): conduction on solid materials (temperature dependence of noble metal Resistor )

Name:……….. ID: ………

Day:………

يدلابلا ةشئاع.أ

The purpose:



  Measuring the Ohmic resistance of a noble metal as a function of temperature at various points.

 Determining the temperature coefficient of resistanceβ

.

Theory:

The following equation applies to the resistance of “normal” metals within the first degree of approximation:

𝑅

_𝜃

= 𝑅

₀

(1 + 𝛽𝜃) (1)

where

R0= Resistance at 0 ,θ: Temperature in C^o R: Resistance at the temperature ⁰C ,𝛽 : is the temperature coefficient of the resistor (resistance change per degree).

In the experiment described here, it will be demonstrated that the functional relationship between ohmic resistance Rθ and

temperature θ is linear function, as required by equation 1. The ohmic resistance of a noble metal resistor will be measured at various

temperatures (intervals from +25 to +230) using a Wheatstone bridge circuit, consisting of a noble metal resistor, a resistance box and a measuring bridge.

If the Wheatstone bridge is balanced for the set temperature, i.e. the bridge branch AB is current- free, then R is given by:

𝑹𝜽 = (𝒍_𝟏

𝒍_𝟐) 𝑹 (𝟐)

Solid state Lab PHYS 485 King Abdulaziz University

Experiment (5): conduction on solid materials (temperature dependence of noble metal Resistor )

Name:……….. ID: ………

Day:………

يدلابلا ةشئاع.أ

when a noble metal resistor is used a linear relation is obtained as the temperature rises.the temperature coefficient β is determined from the slope of the line:

𝜷 =𝒔𝒍𝒐𝒑𝒆 𝑹_𝟎

Result:



⁰

C L

1

cm L

2

cm R



 120

110 100 90 80 70 60 50 40 30 20

1- Plot  vs. R



and find the slope Slope =

^∆𝑹_∆𝜽^𝜽

=

2- Find R

0

= * تاداصلا نم عوطقملا ءزجلا*

3- Find β =

^{𝒔𝒍𝒐𝒑𝒆} _𝑹

𝟎

=

⁰

C

^-1