Physics MCQs for NEET — Practice Questions with Answers

When a PN junction diode is forward biased, the external voltage reduces the potential barrier, causing the depletion region to shrink. Consequently, the barrier height is also reduced, allowing charge carriers to flow across the junction more easily.

$ A_p = { Av^2 \over {R_L \over r_i } } $

The band structure in solids is a result of the Pauli exclusion principle, which states that no two electrons can occupy the same quantum state simultaneously. This principle leads to the formation of energy bands in solids.

When phosphorus, a pentavalent impurity, is added to a semiconductor (typically silicon), it donates extra electrons. This type of semiconductor is called an n-type semiconductor. In an n-type semiconductor, the number of electrons ( _e ext{) is much greater than the number of holes ( _h ext{). Therefore, the correct answer is } n_e ext{) is much greater than the number of holes ( _h ext{). Therefore, the correct answer is } n_e ext{) is much greater than the number of holes ( _h ext{). Therefore, the correct answer is } n_e ext{) is much greater than the number of holes ( _h ext{). Therefore, the correct answer is } n_e > n_h.

A Zener diode is specifically designed to allow current to flow in the reverse direction when a particular, specified voltage is reached. This property makes it very useful as a D.C. voltage regulator. It maintains a constant output voltage despite changes in the load current or input voltage.

The breakdown voltage of a diode can occur due to either avalanche effect or Zener effect. For breakdown voltages less than approximately 5V, the Zener effect is dominant, while for voltages above 5V, the avalanche effect is more significant. Since the breakdown voltage given here is exactly 5V, it can be due to either effect.