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The effect of temperature on resistance of
metal & semiconductor
1- Explain the classical free electron model for metals, and how does it predict temperature
to affect the electrical resistance of metals? Include the relaxation time or mean free
path concept in your discussion and support your answer with equations.
2- What are the basic new ideas that the quantum free electron model introduced
regarding the electrical resistivity of metals?
3- Prove using the quantum free electron model that at high temperature there is a linear
relation between the resistivity of a metal and the temperature?
4- Explain the band theory of solids in general and of semiconductors in particular?
5- According to this theory, what would be the effect of temperature on the conductivity of
a semiconductor?
6- Interpret the result in terms of resistivity and compare with the case of metal?
Object:
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To study the effect of temperature on metal resistance.
To calculate the temperature coefficient of resistance of platinum.
Study the behavior of the resistance of a semiconductor at high temperature.
Determine the energy gap between the conduction band and valance band in an NTC
semiconductor sample
Apparatus:
Electric even
Noble metal resistor
Sensor-CASSY
1 Current supply box
1 NiCr-Ni adapter S
Safety connecting box
98/2000/XP/Vista
Experiment setup
see drawing
Semiconductor resistor
1 CASSY Lab
1 Temperature sensor NiCr-Ni
2 Connecting leads,
1 PC with Windows
Precautions:
We must sure that the thermometer is as close to the sample as possible.
Do not allowed the temperature of sample exceed 160˚C, if this happen please get out the
sample from the oven.
Procedure:
1) Connect the circuit according to the diagram
2) Insert the measuring tip into the hole on the back of the oven so that the tip is in direct
proximity to the resistor element
3) Load settings
4) Start the measurement with F9 (a value pair is recorded for every temperature increase
of 5 K).
5) Switch on the oven.
6) Stop the measurement with F9 at the latest when the temperature reaches 415 K
(approx. 140 °C).
7) Switch off the oven and remove the resistor.
8) When the oven has cooled off repeat the measurement with other resistor.
For a metel
9) Plot the graph R vs. T˚C and calculate its slope.
10) Find (R0 resistance at 0˚ C) from the graph and calculate the temperature coefficient of
resistance for platinum, where
𝜶=
𝒔𝒍𝒐𝒑𝒆
𝑹𝟎
11) find the percentage error ( 𝛼 = 3.9 × 10−3 ℃ )
For a semiconductor
9) Plot the graph R vs. T ˚K
10) Plot the graph Ln( R) vs. T -1 then calculate its slope.
11) Calculate the energy gap for the semiconductor sample from the relation
𝑬𝒈 = 𝟐𝑲 𝒔𝒍𝒐𝒑𝒆
Where K is The Boltezman constant K= 1.38 10 -23 J/K
12) find the error if the energy gap for the sample is Eg 0.48 eV
Question
 what are you note about the metal resistance when the temperature decrease?
 How are you interpret the metal resistance behavior with temperature?
 what are you note about the semiconductor resistance when the temperature increase?
 How are you interpret the semiconductor resistance behavior with temperature?