# Semiconductor Physics – Multiple Choice Questions and Answers

Question-1. During forward bias:
(A) Anode connects to p-side
(B) Anode connects to n-side
(C) Anode is grounded
(D) Cathode connects to p-side

Question-2. Who was nicknamed “The Mayor of Silicon Valley” and credited with the realization of the first integrated circuit or microchip.
(A) Robert Norton Noyce
(B) William Shockley
(C) H. Earle Vaughan
(D) Nicolaas Bloembergen

Question-3. Electron pair bonding occurs when atoms:
(A) share electrons
(B) share holes
(C) share protons
(D) share neutrons

# What is Escape Velocity – Step by Step Derivation

Two planets of radii (R) each, but mass (M) and (4M) have a center to center separation of (6R), as shown. A rocket of mass (m) is projected from the surface of planet of mass (M) directly towards the center of second planet. Obtain an expression for the minimum speed (v) of the rocket so that it reaches the surface of the second planet.

# Comparison of Gravitational, Electric and Magnetic Fields

There is striking similarities between forces of nature. Scientists have classified and identified four fundamental forces of nature: gravitational, electromagnetic, strong nuclear and weak nuclear forces.

We would be discussing the three aspects – gravitational, magnetic and electric forces and fields.

# Variation of Gravitational Potential with Distance

Gravitation potential is defined as work done, which is negative, to bring a point originally at infinite distance from a planet to a point close to it; either on its surface or at some distance exterior to it, or in the planets interior.

# How to Calculate Nuclear Density

Nuclear Density = Mass Density of the Nuclear Matter.

Nuclear Density is Constant.

Value of Nuclear Density is $2.3 \times 10^{17} kg / m^3$

This density also occurs in case of Neutron Stars. A neutron star is a compact star and very dense (rather densest) star known in the Universe. They are entirely composed on Neutrons.

Neutrons are sub-atomic particles which have mass comparable to proton but unlike proton they do not have any electric charge.

Mass of neutron = $1.00866 u ~(1.674 927 \times 10^{-27} kg)$

# Electrical Circuit Theory Problems and Solutions

There are three essential laws governing the electrical circuit. These are Ohm’s Law, Kirchhoff’s Current Law and Kirchhoff’s Voltage Law. Basically these are utilized to solve any electrical circuit problem.

Ohm’s Law states that voltage across a resistance is current passing through it times the resistance. $V=I\times R$

Kirchhoff’s Current Law (KCL)  states that at any junction, the sum of incoming currents is equal to sum of outgoing currents, $\sum I_i=\sum I_o$

Kirchhoff’s Voltage Law (KVL) states that sum of voltage rises is equal to sum of voltage drops around a closed loop, $\sum V_r=\sum V_d$
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# The Photoelectric Effect – Work Function, Threshold Frequency, Planck Constant, Photoelectron, Photon, Stopping Potential, Saturation Current

The Photoelectric Effect: It is a phenomenon in which electrons are emitted when a metal is illuminated with light of frequency greater than a certain frequency called ‘Threshold Frequency’

## Experiments

• Observation by Heinrich Hertz [1857 – 1894]
• Hallwach’s and Lenard’s Observations [1886 – 1902]

## Terminology

• Work Function – The amount of energy required to knock-off the least tightly bound electron of a metal.
• Threshold Frequency – The minimum frequency of the incident light below which photoelectric effect does not happen, even though the intensity of light is raised very high
• Planck Constant   $h ~=~ 6.63 \times 10^{-34} ~J . s$
• Photoelectron – The electron emitted by photons
Photon – ‘The Particle” of light. It has energy $h \nu$
• Stopping Potential – The negative potential which is required to stop the most-energetic electron.
• Saturation Current – The maximum photoelectric current at a particular frequency and intensity of light.

# Greek Alphabets Used in Physics

The following is the table showing the “most commonly used” Greek Alphabets and their typical meaning in Physics. Also lists the Physical Constants which they typically represent. Greek Letter Upper Case Lower Case Commonly Represents in Physics Alpha Angular acceleration … Continue reading Greek Alphabets Used in Physics