Physics 2008 JAMB Past Questions - Question 49: When a pure semicondutor is heated ,its resistance

Correct Answer

B

Explanation

Heating a pure semiconductor increase the mobility of electrons and holes and hence the conductivity. Thus the resistance decease on heating.
When a pure semiconductor, such as silicon or germanium, is heated, its resistance typically decreases. This behavior is in contrast to metals, which generally increase in resistance as their temperature rises. The decrease in resistance of a semiconductor with increasing temperature is due to the intrinsic carrier generation and mobility characteristics of semiconductors.

In a semiconductor, as the temperature rises, more electron-hole pairs are generated. These additional charge carriers increase the conductivity of the material, which leads to a decrease in resistance. This phenomenon is described by the intrinsic carrier concentration equation and is a fundamental property of semiconductors.

The relationship between resistance (R) and temperature (T) in a semiconductor can be approximated by the following equation:

R(T) = Râ‚€ * e^(B/T)

Where:
- R(T) is the resistance at temperature T.
- Râ‚€ is the resistance at a reference temperature.
- B is a characteristic temperature coefficient.
- T is the absolute temperature in Kelvin.

The temperature coefficient B is positive for semiconductors, indicating that resistance decreases as temperature increases.

It's important to note that the specific behavior of a semiconductor may depend on its material properties, impurities, and other factors. However, in most cases, the resistance of a pure semiconductor decreases with increasing temperature. This property is commonly utilized in applications like thermistors and temperature sensors.