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


Electrical components


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
Red or green LEDs are very commonly used in electrical devices (televisions, computers etc.) and serve as controls that indicate operating condition or standby.

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.
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

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

Science class




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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