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Electricity

Free online electricity lessons for elementary school,  middle school and high school.
chemistry high school
 

Science class

Chemistry

Electricity

Optics

Mechanics
Electricity lessons
Electrical components
-Two-terminal electronic components
- Basic electrical components
- Diodes
- What's a resistor ?
- How to determine a resistor value ?
- Resistors effects in circuits
- How to use a resistor ?
- Characteristic curve of a resistor

How to build simple circuits and draw diagrams
- How to build a basic electrical circuit
- How to draw diagrams of electric circuits

The electric current
- Conductors and insulators
- Direction of electric current in a circuit
- The dangers of electricity
- Current intensity - units
how to measure current ?
The Voltage
- The voltage and its units
- How to measure a voltage ?
- Voltage in open and closed circuits
- Rated current and voltage for a lamp
Alternating voltage and current
- Alternating currents effects on led
- What are alternating current and voltage ?
- Periodic alternating voltage and its properties
- Oscilloscope
- Oscillogram
- Frequency
- Measuring RMS voltage with a voltmeter
Serie circuits
- What's a serie circuit ?
- Series circuit properties
- Short circuit in  series circuit
- Current law in series - circuits
- Voltage law in series circuits
Parallel circuits
- What's a parallel circuit ?
- Some parallel circuits properties
- Short circuits in parallel circuits
- Nodes and branches in parallel circuits
- Current laws in parallel circuits
- Voltage laws in parallel circuits
Laws of electricity
- Ohm's law
- Current laws in series circuits
- Voltage laws in series circuits
- Current laws in parallel circuits
- Voltage laws in parallel circuits
Generating electricity
- Voltage for coil wires
What is an alternator ?
- Alternating currents and voltages
- Generating electricity in power plants

Electric power and energy
- Electric power and power rating
- Electric power received by an electrical device
- Electric power consumption by an electrical device
- Relationship between - Electric power and energy


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Electrical components

Diodes

   
1) Diodes and LED

Diodes are two-terminal components.
There are two kinds of diodes:
- The simple diodes.
- Light emitting diodes (LEDs) that operate as simple diodes but emit light when electric current passes.

Diode standard symbol  LED standard symbol
diode standard symbol LED standard symbol 
Comment:
Red or green LEDs are very commonly used in electrical devices (televisions, computers etc.) and serve as controls that indicate operating condition or standby.

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2) The fragility of diodes

Diodes are very vulnerable two-terminal components that are easily damaged by excessive electrical current. So they are never used alone and often protected by two-terminal components called resistors whose roles is to limit the electric current.
Standard symbol of a resistor:  resistor symbol

American standard symbol:  resistor american symbol

3) Diodes and electric current

Diodes and LEDs are polarized so they don't behave the same way if electric current is reversed.
Example:
We realize ​​two circuits that differ only in the sense of connection of a LED

electrical circuit with a diode

We can observe the LED lights in circuit n°1: it is traversed by an electric current.
We can observe that the LED remains off in the circuit n°2: no current flows.


In circuit 1 we say that there's a bypass LED.
In circuit 2 way there's a blocking LED.

We can distinguish a bypass diode and a blocking diode on a diagram by comparing the current direction and the diode symbol: when they are pointing in the same direction there's a bypass diode.

A bypass LED by pass led
A blocking LED blocking led

Comment:

A bypass diode can be compared to an open switch whereas a blocking diode can be compared to a closed switch.
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