Much of Physics in a few seconds

Most interactions in nature are electromagnetic.


For example friction is an electric force. Hence the sparks...


Even swimming at sea is possible because of electric repulsion of say negative charged electrons on water molecules repelling negative charged electrons on our body. Similarly for a ship floating.


Electromagnetic interactions are described by Mawell's 4 equations.


But here is a summary in words. (Firstly said to me by Alekos Soupianos, splendid Physics teacher at school and home who had read Nobel laureate physicist Richard Feynman.)


1
A stationary charge creates an electric field.
For example electrons attracting protons on a condenser microphone membrane when the polarizing voltage is applied between membrane and the electrode behind it creating tension on the membrane.


2
A moving charge creates a magnetic field.
For example when someone speaks to a ribbon microphone.
The ribbon vibrates by he sound. Therefore the free electrons on the aluminium ribbon vibrate. They create a magnetic field which interacts with the magnetic field of the electrons spinning inside the magnets near the ribbon.
The magnetic force sends electrons back and forth to the edge of the ribbon where we get the signal voltage.


3.
An accelerating charge creates an electromagnetic field.
For example electrons accelerating or vibrating on the antenna of a radio station create an e/m wave, traveling at the speed of light in air, which when arriving at the antenna of the radio receiver, electrons inside it move corespondigly and music is received.
Other example, electrons oscillating in the sun make electrons oscillating on objects around us which make electrons oscillate in our eyes, and we see objects around us. Electrons also oscillate inside the metal coating of mirrors (metal coating at the back of the glass) so we can see ourselves.


See also:


The Feynman Lectures on Physics - Feynmann, Leighton, Sands


Richard Feynman on YouTube


Conceptual Physics - Hewitt