Question

Resistance of semiconductor at \[\mathop 0\nolimits^\circ \mathop K\nolimits_{} \] is:
(А) Zero
(B) Infinite
(С) Large
(D) Small

Answer 1

Hint:Semiconductors lie somewhere in between conductors and insulators. They have few free electrons that can lead to the flow of current. Semiconductors are essentially a crystal lattice in which the atoms are grouped close together. Example - Silicon, Gallium, etc.

Complete step by step solution:
Semiconductors are very unique, their ability of conducting electricity can change when impurities are introduced in the crystal lattice (generally a small percentage of another element is added to the semiconductor). The free electrons that can conduct electricity are said to be in conduction band, basically all the electrons in the conduction band have enough energy to move away from their atoms and conduct electricity.
Resistance is defined as the property that opposes the flow of current.

(А) Zero: conductors are the substances that conduct electricity and allow flow of electrons. Even when no heat is provided, they conduct electricity at that point also.
(B) Infinite: increasing the temperature will increase the energy of more electrons, increasing the total number of free electrons in the conduction band, this will result in increase in conductivity and a decrease in resistivity but when temperature is 0 the resistance is infinite
(С) Large: semiconductors conduct electricity but some amount of heat is also required. When no heat is given semiconductors conduct no electricity at all. So instead of having large resistance they have infinite resistance.
(D) Small: only conductors have small resistance. At zero temperature semiconductors do not contain flow of electrons so their conductance is small and not resistant.

Our required option is (B) that is infinite.

Note: We should know that resistance is the opposition offered by the substance to the flow of electric current. The resistance of a conductor depends on the nature of material and temperature. But in the case of a semiconductor, the effect of increase in the number of free electrons per unit volume is much higher than the effect of decrease in relaxation time. So, the resistance of a semiconductor increases with increase in temperature and vice versa.