Ohm’s law The circuit Contiguity Commentary

Georg Ohm electromagnetism

Ohm’s law

• Alessandro Volta’s invention of the battery in 1899
• gave scientists a means to understand electricity.
• Georg Ohm taught mathematics and physics
• in various schools as he tried to improve his position
• by writing a textbook on geometry
• and experimenting with electric circuits.
• He published Die galvanishe Kette,
• mathematisch bearbeitet in 1827
• establishing the law that is named after him,
• that the voltage across a conductor
• divided by the current equals the resistance.

The circuit

• The discovery of Ohm’s law
• would not have been possible without
• Volta’s invention of a continuous source of electricity
• which resulted in his invention of the first electric circuit.
• Benjamin Franklin experimented with lightning in 1749.
• While Volta invented the battery, Alexander Humbolt
• was on the famous voyage on which he discovered
• and experimented with the electric eel.
• Ørsted discovered electromagnetism in 1820;
• Faraday invented the electric motor in 1821.
• Meanwhile, people couldn’t turn lights on by flicking a switch,
• or call each other on the phone, or listen to the radio,
• or watch TV, or refrigerate food without blocks of ice.
• There was no vacuum cleaner or washing machine,
• no digital clock or battery-powered watch,
• no toaster, no food processor, no microwave oven,
• no flashlight, no electronic calculator, and no computer.

Contiguity

• Georg Ohm argued against “action at a distance.”
• The electromagnetic force applied
• across contiguous particles, he said.
• By 1600 William Gilbert realized
• electric attraction is not a disturbance of the air.
• So one might ask, “Particles of what?”
• A person’s senses are only so refined.
• One cannot see, one cannot count, one cannot smell
• each unknown particle impelling its neighbors.
• And the force communicates across empty space
• like light, whether it’s a wave or a stream of particles,
• moving, faster than thought, at the speed of light.