NEET Practice Questions (MCQs) with Answers & Solutions

To find the value of the limiting resistor ( $R$ ) for an LED, we use Ohm's law. Given the parameters: the voltage drop across the LED ( $V_{LED} = 2V$ ), the current through the LED ( $I = 10 mA$ ), and the supply voltage ( $V_{supply} = 6V$ ). The resistor value can be calculated as follows:

$$R = \frac{V_{supply} - V_{LED}}{I}$$

Substituting the values:

$$R = \frac{6V - 2V}{10 mA}$$

$$R = \frac{4V}{10 mA}$$

$$R = 400 \Omega$$

Thus, the value of the limiting resistor is $400 \Omega$ .

A NAND gate is considered a universal gate because it can be used to implement any Boolean function without needing to use any other type of gate. This makes it extremely versatile in digital circuit design.

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

Frequency of LC oscillator is $ f = { 1 \over 2 \pi \sqrt {LC } } $

$ Output voltage = voltage gain \times Input voltage $ $ There will be a phase difference of 180 ^\circ between input and output signal $