Nek Singh Yadav

teacher | Physics Maths


Hi, I am Nek Singh Yadav, an M.Sc Physics post graduate having a very rich experience in teaching for around 25+ years.Comfortable in both Hindi and English medium students from Class 9th to B.Sc and M.Sc.




7+ Years

Teaching Classes


Current Organization

Cross Product of Two Vectors in Terms of Components, L-39, Class 11

Cross Product of Two Vectors, L-38, Class 11

Expression for Angle Between Two Vectors, L-37, Class 11

Dot Product in Terms of Components, L-36, Class 11

Dot Product of Two Vectors , L-35, Class -11

Energy Loss In Transformer, L-153, Class-12

Transformer, L-152, Class-12

Power Factor of AC Circuit, L-151, Class-12

General Discussion on Power Consumption in LCR Series Circuit, L-150, Class-12

Power Consumed in LCR Series Circuit

Resonance in LCR Circuit,L-148, Class-12

Impedance of LCR Circuit, L-147, Class-12

LCR Series Circuit Connected to Alternating Current, L-146, Class-12

Capacitor Connected to an AC Source, L-145, Class-12

AC Applied to an Inductor, L-144, Class-12

AC applied to a Resister, L143, Class- 12

Phasor and Phasor Diagram, L-142, Class-12

RMS Value of AC, L-141, Class-12

Mean Value of AC, L-140, Class-12

Alternating Current, L-139, Class-12

AC Generator, L-138, Class-12

Mutual Induction of Two Co-axial Coils, L-137, Class-12

Mutual Induction, L-136, Class-12

Energy Stored in an Inductor, L-135 , Class-12

Self Induction, L-134, Class-12

Motional EMF Induced in a Conduction Rod Rotsted Perpendicular to Magnetic Field, L-133, Class-12

Induced EMF by Changing Area, L-132, Class-12

Lenz's Law in Electromagnetism, L-131, Class-12

Faraday's Laws of Electromagnetic Induction, L-130, Class-12

Magnetic Flux, L-129, Class-12

Magnetic Elements of Earth, L-128, Class-12

Resolution of a Vector into It's Three Components, L-34, Class-11

General Features of Earth's Magnetism,L-127, Class-12

Resolution of a Vector into It's Two Perpendicular Components, L-33, Class-11

Analytical Method of Vector Addition,L-32, Class-11

Some Definitions of Vectors, L-31, Class-11

Gauss Law In Magnetism

Scalar and Vector Quantities, L-30, CLASS-11

Magnetic Moment and it's Dipole Moment, L-125, CLASS-12

Magnetic Field & Magnetic Lines of Force, L-124, CLASS-12

Bar Magnet and properties of Bar Magnet

Magnetic Moment of a Revolving Electron, L-122, CLASS-12

Current Loop as a Magnetic Dipole & Expression for it's Dipole Moment, L-121, CLASS-12

Relative Velocity, L-29, Class-11

Conversion of Galvanometer into Ammeter & Voltmeter, L-121, Class-12

Moving Coil Galvanometer, L-120, Class-12

Equation of Motion by Calculus Method, L-28, Class-11

Equation of Motion by Graphical Method, L-27, Class-11

Torque on Current Carrying Rectangular Loop Placed in an Uniform Magnetic Field, L-119, Class-12

Acceleration by Velocity-Time Graph, L-26, Class-11

Force Between Two Parallel Straight Infinite Long Current Carrying Conducts, L-118, Class-12

Acceleration, L-25, Class-11

Displacement-time Graph for Non Uniform Motion, L-24, Class-11

Magnetic Field Due to a Current Carrying Toroid, L-117, Class-12

Displacement Is Equal to Area under V-T Graph for Uniform Motion, L-23, Class-11

Solenoid & Magnetic Field Inside It Using Ampere's Law, L-116, Class-12

Displacement-Time Graph, L-22, Class-11

Magnetic Field Due to a Current Carrying Circular Infinite Long Wire Using Ampere's Law, L-115, C-12

Instantaneous Speed & Instantaneous Velocity, L-21, Class-11

Ampere's Circuital Law, L-114, Class-12

Speed and Velocity, L-20, Class-11

Magnetic Field on the Axis of a Current Carrying Loop, L-113, Class-12

Magnetic Field at the Center of a Current Carrying Loop, L-112, Class-12

Distance and Displacement, L-19, Class-11

Motion in One, Two or Three Dimensions, L-18 , Class-11

Rest and Motion, L-17, Class-11

Biot-Savsrt's Law, L-111, Class-12

Velocity Selector/Velocity Filter, L-110, Class-12

Motion of a Charged Particle in an Uniform Magnetic Field, L-109, Class-12

Error in Physical Quantities Having Powers, L-16, Class-11

Charged Particle Moving in an Uniform Electric Field, L-108, Class-12

Error in Division of Physical Quantities, L-15, Class-11

Error in Multiplication, L-14, Class-11

Errors in Addition and Subtraction of Two Physical Quantities, L-13, Class-11

Error in Measurement of Physical Quantities, L-12, Class-11

Force on a Current Carrying Conductor Placed in an Uniform Magnetic Field, L-107, Class-12

Lorentz Force, L-106, Class-12

Algebraic Operations and Significant Figures, L-11, Class-11

Rounding off the Measurements, L-10, Class 11

Magnetic Field & Magnetic Force, L-105, Class 12

Significant Figures - Class 11

Nature of Magnetic Field L - Class 12

4rth Use of Dimensions

Oersted's Experiment - Class 12

2nd &3rd Useses of Dimensions

Uses of Dimensions

Dimensions of Physical Quantities, Class-11

Derived Units & Order of Magnitude , Class-11

Numericals on Kirchhoff's Law

Fundamental Physical Quantities & Units

Numericals on Resistance & Potential II

Numericals on Resistance & Potential I

Electromagnetic, Strong & Weak Nuclear Forces

Numericals of Current Electricity on Resistance & Resistivity

Physics of Class Xi, Introduction to Science, Physics & Gravitational Force-1

Numericals on Capacitance (IV)

Numericals on Potential & Capacitance (III)

Numericals on Potential & Capacitance (II)

Numericals on Potential & Capacitance (I)

Numericals on Charge & Field (4rth Video)

Numericals on Charge & Field (3rd Video)

Numericals on Gauss's Law

Numerical on Electric Charge & Electric Field

Experimentally - Measurement of Internal Resistance of a Cell Using Potentiometer

Experimentally Comparison of Emf's of Two Cells Using Potentiometer

Measurement of Internal Resistance of a Cell Using Potentiometer

Comparison of EMF's of Two Cells Using Potentiometer

Potentiometer & It's Principle

To Find Resistance of a Wire Using Meter Bridge and Hence Determine the Resistivity of Material

Meter Bridge or Slide Wire Bridge

Measurement of Temperature Using Wheatstone Bridge

Wheat Stone Bridge

Kirchhoff's Laws

Mixed Groupings of Cells

Parallel Groupings of Cells

Series Groupings of Cells

Relation Between EMF & Terminal Potential Difference

Cell, EMF and Internal Resistance of a Cell

Combination of Resistors

Resistor & Color Code Carbon Resistor

Electric Energy and Power

Relation among Current Density, Conductivity & Electric Field

Conductance & Conductivity

Electric Current Density

Effect of Temperature on Resistivity & Temperature Coefficient of Resistivity

Factors Affecting the Electrical Resistivity

Ohm's Law from First Law

Resistivity/Specific Resistance

Ohm's Law

Relation Between Electric Current & Drift Velocity


Electric Current & Drift Velocity

Electric Charge

Electric Field Intensity on Axial Line Due to a Dipole

Capacitance of a Parallel Plate Capacitor Filled with Dielectric

Electric Displacement Vector

Dielectric Strength


Relation Between Polarization Vector and Induced Surface Charge Density

Polarization Vector/Polarization Density

Dielectric and Relation Between Surface Charge Density & Induced Surface Charge Density

Dielectric and It's Polarisation

Polarizability of a Molecule

Polar and Non Polar Substance & Their Polarisation

Loss of Energy on Sharing of Charges

Redistribution of Charges/Common Potential

Energy Density of a Capacitor

Electric Energy Stored in a Capacitor

Grouping of Capacitors

Capacitance of a Parallel Plate Capacitor

Parallel Plate Capacitor and Its Principle

Capacitance of Isolated Spherical Conductor


Electric Capacitance

Discharge Action at Sharp Point (Corona Discharge)

Electrostatic Shielding

Electric Potential Is Constant for the Entire Surface

Charge Resides on the Surface of a Conductor

Net Electric Field in the Interior of Conductor Is Zero and Electric Field Perpendicular to Surface

Net Charge in the Interior of Conductor Is Zero

Conductors and Insulators

Electric Potential Energy Of A Electric Dipole

Electric Potential Energy In An External Field

Electric Potential Energy

Equipotential Surface

Electric Field Intensity as Gradient of Potential - 28

Electric Potential Due To A Dipole At Any Point

Electric Potential Due To A System Of Point Charges

Electric Potential Due To A Point Charge

Electric Potential And Potential Difference

Electric Field Due To A Charged Spherical Shell

Electric Field Intensity Due To Two Parallel Infinite Plane Charged Sheets

Electric Field Intensity due to Infinite Charged Plane Sheet - 21

Electric Field due to a Infinite Long Straight Charge Wire - 20

Coulombs Law From Gauss's Law - 19

Gauss Law / Gauss Theorem - 18


Electric Field Lines

Energy Of A Dipole In An Electric Field - 16

Electric dipole in uniform electronic field -15

Electric Field Due To A Charged Ring-14



Electric dipole - 11

Electric Field

Force Due To Continuous Distribution Of Charge

Continuous Charge Distribution

Coulomb's law - Vector form and position vector form.

Superposition of Principle of Forces

Basic Properties of Electric Charge

1. Additive Nature of Charge: The net charge on a body is the vector sum of all the charges distributed in whole of the body in different parts.

 If q1, q2, ………. qn are the charges on a body then net charge q = q1 + q2 + …. + qn

 Example A system containing +2q, -3q and +8q,

Total charge q = +5q.


2. Conservation of Charge: The net charge on a system remains constant, it may move in a different part of the system. A charge can neither be created nor can be destroyed.

 e.g, Pair production = electron (-e) + proton (+e)


3. Quantization of Charge: The net charge on a body is integral multiple of basic charge e.

So q = +-e +-2e +- 3e +- ……

Ray Optics and Optical Instrument - Lateral Shift Expansion

From below figure, Let AB is an incident ray, incident on a glass plate of thickness BM2 is the normal. The ray reflects to the path BC in the glass plate, and at point this ray emerges out CD. If we draw un deviated path of incident ray, then it goes to the path BE. If we draw a perpendicular from point C on this ray, it meets at point K.



Ray Optics and Optical Instrument - Critical Angle and Total Internal Reflection

Critical Angle: When the ray of light goes from denser to rare medium, it bends away from the normal and as the angle of incidence in denser medium increases, the angle of refraction in rare medium also increases at a certain angle, then angle of refraction becomes 90°. This angle of incidence is called Critical Angle.

Formula, according to snell’s law

Total Internal Reflections: When angle of incidence exceeds the critical angle then light may come back into the same medium after reflection from interface. This phenomenon is called Total Internal Reflection.

Application of Total Internal reflection:

1. Mirage: There is the optical illusion in hot places or at cool solid road in summer days. This is due to total internal reflection. In this process the inverted image is produced, so a possibility of water is inverted but there is no such place of water.

The inverted image is formed due to the total internal reflection.

Reflection of the space above the earth is divided into the layers. The layers near to the earth surface are rare and optical density increase upward.


Hence, the ray of the light starts from point A of the tree goes several refractions from denser to rare and its incident angle increases regularly. At a particular incident angle becomes more than critical angle, the ray goes back external reflection and its image is seen by the observer at point A.


2. Brillians of Diamond: The refractive index of diamond 2.42

Hence the critical angle

Due to small critical angle and the shape made by cutting, so that incident angle is always greater than Critical angle hence due to multiple total internal reflection, the transmitted light is more bright.

3. Optical Fibre: It has three parts.

  1. Core
  2. Cladding
  3. Cover


Construction: The centre wire is made of glass or quartz through which optical rays passes its refractive index. About 1-5 another material surrounding it is called Cladding. Its refractive index is less then the refractive index of the core. It is around 1.48. The whole combination is provided by plastic cover.

Working: When the signal of optical waves incident on an angle greater than critical angle, it gets total internal reflection. At the interface of core and cladding this way optical waves is transmitted from one place to another places.


  1. Communication
  2. Internet
  3. Lightning & decoration

4. Totally Reflection Prism: Totally reflection prism is isosceles prism which one angle 90° and other at 45° each.

Working: There are two types of internal reflection, 90 and 180 degrees. The refractive index of prism glass material is 1.5 and its critical angle 41.8°.


  1. Deviation 90°: When the ray of light PQ falls perpendicular to the surface AC, it passes un deviated from the surface and falls at an angle 45°. On AB surface since incident angle is more than critical angle hence it gets total internal reflection and goes to the path QK. That the incident ray gets deviation by angle 90°
  2. Deviation 180°: Here ray deviation two times by 90° so it is called 180° deviations.


Ray Optics and Optical Instrument - Reversibility of Light

Law of Reversibility: When the ray of light reverse back to its own path after refraction and reflection, this phenomenon is called Reversibility.

Ray Optics and Optical Instrument  - Reversibility of Light

Multiply both equation.

1n2 X 2n1 = 1

When the light ray passes though multi medium

At 1st Interface

At 2nd Interface

At 3rd interface

Ray Optics and Optical Instrument  - Reversibility of Light

Ray Optics and Optical Instrument  - Reversibility of Light

Multiplying equation (i), (ii) & (iii)