Electron | MCQs

Explanation

The word "transistor" is derived from "transfer" and "resistor".

It signifies the transfer of resistance — specifically, it controls a large output resistance using a small input resistance.

In essence, a transistor transfers a signal from a low-resistance circuit to a high-resistance circuit, acting as an amplifier or switch.

Explanation

 A PN junction diode allows current to flow only in one direction — from P to N (forward bias).

During the positive half cycle of AC, the diode is forward-biased (low resistance), so current flows.

During the negative half cycle, the diode is reverse biased, so it blocks current and offers high resistance.

Explanation

Thermistors are temperature-sensitive resistors whose resistance changes with temperature.

This change affects the electrical voltage in a circuit, allowing temperature measurement.

Explanation

In a Cathode Ray Oscilloscope (CRO), the brightness of the spot is controlled by the intensity of the electron beam.

This intensity is regulated by the voltage on the anodes, hence anodes control brightness.

Explanation

An ideal op-amp has very high input resistance, often in the megaohms range.

This prevents it from drawing current from the input source.

Explanation

A semiconductor diode has 2 terminals: anode (positive) and cathode (negative).

It allows current to flow in one direction only, functioning as a rectifier.

Explanation

Capacitance depends on area of plates, distance between them, and the dielectric (medium) used.

It does not directly depend on the electric field, which is a result of the charge and voltage, not a factor in determining capacitance.

Explanation

 The temperature coefficient of resistance indicates how the resistance of a material changes with temperature.

In semiconductors, as temperature increases, more charge carriers (electrons and holes) become available, so resistance decreases.

Therefore, the temperature coefficient is negative.

Explanation

The Fermi energy is the highest energy level that electrons occupy at absolute zero temperature.

Above this energy, states are empty, and below it, they are filled.

Explanation

When an electron moves perpendicular to a magnetic field, the electromagnetic force (also known as the Lorentz force) acting on the electron is given by the formula:

F=qvBsin(θ)

Where:

• $F$ is the force,
• $q$ is the charge of the electron,
• $v$ is the velocity of the electron,
• $B$ is the magnetic field strength,
• $$θtheta is the angle between the velocity vector and the magnetic field.

When the electron is moving perpendicular to the magnetic field, $theta = 90^circ$ and $sin(90^circ) = 1$

Therefore, the force becomes:

$$F=qvB$$

This means the force is at its maximum value since both the charge and the velocity contribute to the force. Thus, the statement that the force acting is maximum is correct.