Question

A piece of semiconductor is connected in series in an electric circuit. On increasing the temperature, the current in the circuit will ______.

• A. decrease.
• B. remain unchanged.
• C. increase.
• D. stop flowing.

Hint:

This property is why semiconductors undergo "thermal runaway" and physically melt if not cooled properly. Higher temp $\rightarrow$ lower resistance $\rightarrow$ higher current $\rightarrow$ more Joule heating ($I^2R$) $\rightarrow$ even higher temp!

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks how the electrical current passing through a semiconductor changes when its physical temperature is raised.

Step 2: Detailed Explanation:
Materials behave fundamentally differently under thermal stress based on their band gap structure:
1. Conductors (Metals): As temperature increases, lattice atoms vibrate more aggressively, increasing collision rates with drifting electrons. This drastically increases resistance, causing the current to decrease.
2. Semiconductors (Silicon, Germanium): At absolute zero, they act as perfect insulators because all electrons are locked tightly in covalent bonds (the valence band is full, conduction band is empty).
As thermal energy (temperature) increases, it provides enough energy to break these covalent bonds, exciting electrons across the band gap into the conduction band and leaving behind mobile 'holes' in the valence band.
This massive influx of newly created charge carriers (both electrons and holes) causes the electrical conductivity to soar. The resistance of a semiconductor drops exponentially as it heats up (it has a negative temperature coefficient of resistivity).
Consequently, for a fixed applied voltage, a drop in resistance results in an increase in circuit current.

Step 3: Final Answer:
The current in the circuit will increase, matching option (c).