Physics MCQs for NEET — Practice Questions with Answers

In intrinsic semiconductors, the number of electrons (y) is equal to the number of holes (x). This is because intrinsic semiconductors are pure and have no impurities, so the generation of electron-hole pairs is balanced.

Decreasing the temperature of a semiconductor increases its resistivity. This is because lower temperatures reduce the thermal energy available to generate electron-hole pairs, thereby reducing the number of charge carriers.

A Light Emitting Diode (LED) operates only in forward bias. In forward bias, the LED allows current to pass through and emits light. Varactor diodes, Zener diodes, and photodiodes either operate in reverse bias or can operate in both forward and reverse bias depending on their specific applications.

Only solar- cell generates e.m.f and it does not need bias -voltage

In forward bias mode, the P-N junction diode allows current to flow easily, resulting in a lower resistance. Therefore, the resistance of a P-N junction diode in forward bias is 'less'.

$ v_d = { I \over nAe } $ $ \therefore v_d \alpha { I \over n } $

In a P-type silicon, holes are the majority charge carriers, and the dopants are trivalent atoms. This is because trivalent atoms create 'holes' by accepting electrons.

A Zener diode is used as a voltage regulator by operating it in reverse bias. In this configuration, the Zener diode is connected in parallel with the load to maintain a constant voltage across the load. This is because in reverse bias, the Zener diode maintains a constant voltage (Zener voltage) across it once the breakdown voltage is reached.

$ E = { v \over d } = { 0.6 \over 10^{-6}} $