Variation Of The Resistance With Temperature

Introduction to the Variation of the Resistance with Temperature

The temperature coefficient of resistance is a parameter that describes how the resistance of a material changes with temperature. For metals, the resistance increases approximately linearly as the temperature increases.

Aim Of The Temperature Coefficient Of Resistance Experiment

-Measurement the Variation of the Resistance of a wire with Temperature.

-Measurement of The Temperature Coefficient of Resistance.

Tools Of The Temperature Coefficient Of Resistance Experiment

Metre (Wheatstone) bridge
Dry cell
Resistance box
Sensitive galvanometer with protective resistance
Thermometer (0–100 °C, graduated to 0.5 °C)
Beaker
Ice
Test tube containing a coil of wire immersed in paraffin
Approximately 2 m of iron wire (S.W.G. 34 D.C.C.) for the coil

Steps And Method of The Experiment

Immerse the test tube in a beaker containing finely crushed ice and water.

Leave it for some time until the temperature reaches approximately 0°C.

Connect the metre bridge circuit as shown in the diagram.

When the thermometer indicates approximately 0°C, determine the resistance of the coil using the metre bridge.

Adjust the resistance box to obtain a balance point near the middle of the bridge wire.

Record the temperature and resistance. Replace the ice-water mixture with tap water and determine the resistance again.

Record the temperature immediately after obtaining the balance point. Slowly heat the water bath using a low Bunsen flame.

Measure the resistance of the coil at approximately 10°C intervals, recording the exact temperature for each measurement.

Temperature Coefficient of Resistance Experiment: Theory

Parameters, Graph & Final Law

Increase in resistance of a resistance

Resistance measured

Rise in temperature

Unit of measurement of the temperature

Temperature

°C

First length

Remaining length

Final resistance

Final Law

α = PNOC · OM K⁻¹

Table of readings for the variation of the resistance with temperature

Table of the Readings

Rx = L1L2 × 20Ω

θ/°C	L1/cm	L2/cm	Rx/Ω

Medical Application

Understanding the variation of the resistance with temperature has direct applications in medical device engineering, particularly where components must maintain stable, predictable performance:

For a diode laser to maintain stable frequency, output power, current, and temperature, its operating parameters must be carefully regulated. A low-cost, low-noise current source can provide the stable current required for laser operation. The current-sense resistor is a critical component and should have high power capacity, low thermal EMF, and minimal temperature dependence. Therefore, a low-cost, high-precision resistor is needed to ensure reliable laser stability.

Frequently Asked Questions About the Variation of the Resistance with Temperature

Why is the coil immersed in ice water at the start of the experiment?

Starting near 0°C gives a stable, well-defined reference point. Measuring resistance at this known baseline temperature makes it possible to accurately track how resistance changes as temperature rises through the rest of the experiment.

Why does resistance increase with temperature in metals?

As temperature rises, atoms in the metal vibrate more vigorously, increasing collisions with the free electrons carrying current. These extra collisions impede electron flow, which is measured as an increase in resistance.

Why is a low temperature coefficient desirable for precision resistors, like those used in laser diode circuits?

A resistor with a near-zero temperature coefficient maintains a stable resistance value even as its operating temperature fluctuates, which is essential for applications like laser diodes that require a highly stable current to maintain consistent frequency and output power.

Variation of the resistance