# Physics Video Lectures

Here you will find 29 free physics video lectures. These are also great for use at school and university. Do you need a Universaldenker style physics video on a specific topic? Then you can order a physics video.
Video
Level 2 (without higher mathematics)

## The 5 Differences Between Parallel and Series Circuit

Die 5 wichtigsten Unterschiede zwischen einer Parallel- und Reihenschaltung von Widerständen oder Leitwerten.

Content of the video
1. 00:00 Introduction
2. 00:16 Difference: Connection
3. 00:47 Difference: Current
4. 01:21 Difference: Voltage
5. 02:00 Difference: Resistance
6. 02:33 Difference: Conductance
Video
Level 2 (without higher mathematics)

## Difference Between Partial and Total Derivative

Here you will learn by example what the difference is between the partial derivative and the total derivative.

Video
Level 2 (without higher mathematics)

## 7 Differences between an Electric and Magnetic Field

Here you will learn 7 important differences between the electric field (E) and the magnetic field (B).

Video
Level 4 (for physics pros)

## Fourier Series. An Intuitive Explanation.

In this video you will learn what Fourier series / coefficients are and how to specify / calculate them for a function.

Content of the video
1. 00:00 Why Fourier series?
2. 01:08 The concept of Fourier series
3. 03:05 Fourier coefficients
4. 06:15 Fourier basis
5. 09:38 Example: Sawtooth function
Video
Level 3 (with higher mathematics)

## Euler-Lagrange Equation

In this physics video on analytical mechanics you will learn what the Euler-Lagrange equation is good for and how to use it (+ example).

Content of the video
1. 00:00 Why all this?
2. 00:52 Action Functional
3. 01:53 Nature is extemal
4. 02:44 Calculate the action
5. 03:52 Structure of the Euler-Lagrange equation
6. 05:20 Lagrange function
7. 05:54 How to use Euler-Lagrange equation
Video
Level 3 (with higher mathematics)

## Dirac's Delta Function

In this video you will learn what the Dirac delta function is. We also derive its properties and make examples.

Content of the video
1. What is the delta function good for?
2. 02:09 Delta function graphically
3. 02:21 Integral of the delta function at the origin
4. 03:08 Shifted delta function
5. 03:41 Integral of the shifted delta function
6. 04:33 Delta function is symmetric (even)
7. 05:44 Delta function with a factor
8. 06:38 Examples
9. 07:52 Three-dimensional delta function
Video
Level 2 (without higher mathematics)

## Photoelectric Effect and The Einstein Formula Simply Explained

Here you will learn what the photoelectric effect is, how it can be described with a Einstein formula + everything you need to know about it.

Content of the video
1. 00:00 What is the photoelectric effect?
2. 00:07 Experiment setup
3. 00:46 Photons
4. 01:58 Work function and threshold frequency
5. 03:48 Convert electron volts to joules and vice versa
6. 04:19 Kinetic energy of an electron
7. 04:50 Einstein formula
8. 05:36 Stopping (braking) voltage
9. 07:20 Energy frequency graph
Video
Level 4 (for physics pros)

## Electromagnetic Wave Equation Simply Explained

In this physics video, we first derive the two wave equations for an electromagnetic wave (for the E and B field components) and look at their properties.

Content of the video
1. 00:00 Maxwell's equations in vacuum
2. 00:27 Derivation of the EM wave equation
3. 02:13 Velocity of an electromagnetic wave
4. 03:17 Structure of the electromagnetic wave equation
5. 05:00 E- and B-field are perpendicular to wave vector
6. 07:24 E- and B-field are perpendicular to each other
7. 08:15 Summary
Video
Level 3 (with higher mathematics)

## Hermitian Operators Simply Explained

In this physics video you will learn what Hermitian operators and matrices are and what important properties they have.

Content of the video
1. 00:00 Motivation: Real mean values
2. 01:16 What are Hermitian operators?
3. 02:16 What is a self-adjoint operator?
4. 02:56 Notation of a Hermitian operator
5. 03:20 Eigenvalues are real
6. 04:27 Eigenvectors are orthogonal
7. 05:56 Eigenvectors form a basis
8. 06:37 What is a Hermite matrix?
9. 07:19 Examples for (non) Hermitian matrices
Video
Level 2 (without higher mathematics)

## Lorentz force simply explained in 6 minutes!

In this video you will learn how to determine the direction of the Lorentz force using left/right hand rule and how this force is calculated and related to the centripetal force.

Content of the video
1. 00:00 What is Lorentz force?
2. 00:28 Moving charge perpendicular to the magnetic field
3. 01:12 Determine Lorentz force direction
4. 02:40 Lorentz force qvB-equation
5. 04:12 Movement at an angle to the magnetic field
6. 04:59 Lorentz and centripetal force
7. 06:20 Determine velocity of the electron