Learning physics and chemistry easily and freely - Science for elementary school, middle school and high school

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


The electric current

Dangers of electricity

1) The human body and its conductivity

The human body is a bad conductor (he would give a negative result with the conductivity test) but it is not totally insulated and can still be traversed by an electric current.

2) Dangers of the current depends on the voltage

The electric current is higher if the voltage is high.
- It is considered that in general 24 V is the voltage security: below this voltage we do not feel dangerous effects of electric current.
- Above 70 V there is a risk of death if contact is made with wet hands.

3) Electric shock and its effects

When a human body is traversed by an electric current, we say it suffers an electric shock.
An electric current may also cause an electrocution if the result is death.Electric shock can cause effects varying from simple tingling to respiratory paralysis, cardiac arrest, burns on the skin or internal organs, as well as involuntary muscle contractions.

4) Essential precautions

To prevent electric shock or electrocution it is necessary to take some essential precautions:
- Avoid handling electrical appliances in the presence of water.
- Do not strip electric wires.
- Remember to turn off power before changing a lamp.
- Do not push objects into electrical outlets and make them inaccessible to young children.
- Do not open any electrical appliance in use.

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


©2021 Physics and chemistry