In special and general relativity, the four-current (technically the four-current density) is the four-dimensional analogue of the electric current density. Also known as vector current, it is used in the geometric context of four-dimensional spacetime, rather than three-dimensional space and time separately. Mathematically it is a four-vector, and is Lorentz covariant. Analogously, it is possible to have any form of "current density", meaning the flow of a quantity per unit time per unit area. see current density for more on this quantity. This article uses the summation convention for indices. See covariance and contravariance of vectors for background on raised and lowered indices, and raising and lowering indices on how to switch between them. (Wikipedia).
System of Equations with Three Equations and Three Variables
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From playlist Systems of Equations
The Definition of a Linear Equation in Two Variables
This video defines a linear equation in to variables and provides examples of the different forms of linear equations. http://mathispower4u.com
From playlist The Coordinate Plane, Plotting Points, and Solutions to Linear Equations in Two Variables
Modification of "Spherical 4R mechanism 2a" and "Spherical 4R mechanism 2b". Because it is a combination of two spherical 4R joints, angles between line connecting two joint centers and the shaft axles must be set equal to each other in order to get constant velocity.
From playlist Mechanisms
How five port four way valve works air - air
http://www.mekanizmalar.com This video shows working principle of five port four way valve. Left and right pilot ports have connection for pilot air.
From playlist Pneumatic and Hydraulics
Systems of Equations in Three Variables: Part 2 of 2
This video provides examples of a system with no solution and infinite solutions. The answers are verified graphically. http://mathispower4u.wordpress.com/ (searchable) http://mathispower4u.yolasite.com/ (list of all videos)
From playlist Systems of Equations with Three Unknowns
C34 Expanding this method to higher order linear differential equations
I this video I expand the method of the variation of parameters to higher-order (higher than two), linear ODE's.
From playlist Differential Equations
Systems of Equations Two Variables Two Equations Infinitely Many Solutions
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From playlist Systems of Equations
How five port four way valve works air - spring
http://www.mekanizmalar.com This video describes working principles of a five port four way valve. This valve's spool shift from natural position with air pressure and return to natural position by spring.
From playlist Pneumatic and Hydraulics
AS Physics Exam Question: Electricity
Examples of exam questions at Physics AS level for Electricity covering Edexcel, AQA and OCR material.
From playlist A Level Physics Exam Questions - Worked Examples
Intermediate Series and Parallel Resistor Circuit Demos and Animations
A detailed look a combination series and parallel resistor circuit. Includes a demonstration of the real circuit and an animation of the electric potential energy of the charges as they move through the circuit. Want Lecture Notes? https://www.flippingphysics.com/series-parallel-resistor-i
From playlist All of AP Physics C: Electricity & Magnetism!
Electrical Engineering: Ch 8: RC & RL Circuits (45 of 65) General Strategy Solving RL Circuits Ex.6B
Visit http://ilectureonline.com for more math and science lectures! In this video I will find the voltage across the capacitor(t=0)=?, voltage across the capacitor(t=infinity)=?, the time constant=?, current across the inductor=? of the RL circuits. (Example 6B) Next video in this series
From playlist ELECTRICAL ENGINEERING 8: RC AND RL CIRCUITS
Determine the Current of Four Circuits with Resistors
This video provides and example on how to find the currents of 4 connected circuits.
From playlist Augmented Matrices
This physics video tutorial provides a basic introduction into the current divider circuit. It explains how to calculate the current flowing through each resistor in a two resistor parallel circuit using a simple formula given the total current entering the circuit. It also includes exam
From playlist New Physics Video Playlist
Electrical Engineering: Ch 3: Circuit Analysis (35 of 37) Solving Basic Transistor Circuit (MESH) 2*
Visit http://ilectureonline.com for more math and science lectures! In this video I will used the MESH method to find the voltages across a 200ohm resistor and across the collector and the emitter of a transistor circuit. Next video in this series can be seen at:
From playlist ELECTRICAL ENGINEERING 3 CIRCUIT ANALYSIS
This electronics video tutorial provides a basic introduction into the superposition theorem. It explains how to solve circuit problems with multiple voltage and current sources using the superposition theorem. My Website: https://www.video-tutor.net Patreon Donations: https://www.patr
From playlist New Physics Video Playlist
Electrical Engineering: Ch 4: Circuit Theorems (6 of 35) Superposition Property Ex. 1
Visit http://ilectureonline.com for more math and science lectures! In this video I will find the V=? and i=? at a node of a circuit with 2-voltage sources. Next video in this series can be seen at: https://youtu.be/FQX_pfFMIf0
From playlist ELECTRICAL ENGINEERING 4: CIRCUIT THEOREMS
Negative Resistance In NPN 2N2222A Transistor
This electronics video tutorial provides a basic introduction into the concept of negative resistance which is exhibited by devices such as the tunnel diode and the 2N2222A NPN transistor. Esaki Oscillator: https://www.youtube.com/watch?v=wP5Sw76myNM My Website: https://www.video-tutor.
From playlist Electronic Circuits
Polynomials with Trigonometric Solutions (2 of 3: Substitute & solve)
More resources available at www.misterwootube.com
From playlist Using Complex Numbers
RC Circuits (4 of 8) Charging a Capacitor, Time Constant, Voltage, Current, An Explanation
RC time constant explained is with respect to the voltage and the current in a capacitor charging circuit.
From playlist DC Circuits, RC and RL Circuit Analysis