Investigation of the Effect of Temperature on the Electrical Resistance of Carbon Resistors

The temperature dependence of electrical resistance is a fundamental physical property with broad implications for electronic circuit design, precision instrumentation, and thermal sensing applications. Carbon composition resistors, widely used in Nigerian educational and commercial electronic applications, exhibit a negative temperature coefficient of resistance that differs from the positive coefficient of metallic conductors. This study investigates the effect of temperature on the electrical resistance of five commercial carbon resistor types (1 kOhm to 1 MOhm) obtained from computer village markets in Lagos, South West Nigeria. Resistance is measured using a precision four-wire Kelvin bridge at temperatures ranging from 20 to 120 degrees Celsius in a temperature-controlled oven. The temperature coefficient of resistance is extracted by linear regression of the resistance-temperature data for each sample. Results indicate temperature coefficients ranging from negative 150 to negative 820 parts per million per degree Celsius across the resistor types. Deviation from the datasheet-specified values averages 12 percent, suggesting batch-to-batch manufacturing variability in products available in the Nigerian market. The study recommends temperature-coefficient verification testing before deploying carbon resistors in precision circuits operating under tropical ambient conditions. Keywords: temperature coefficient, carbon resistor, electrical resistance, Lagos, electronic components