Key Terms
Electric charge
A physical property of matter that causes objects to attract or repel each other. Produces and responds to electromagnet
Two types only
Positive and negative. No third type exists.
Even in particle physics
When a charged particle is created, an equal and opposite charge is always created simultaneously. An electron and a pos
Conductor
Material with free electrons that move easily through it. Metals are the prime example.
Insulator
Material where electrons are tightly bound and cannot move freely. Glass, rubber, dry wood, pure water, dry table salt.
Electric field
A vector quantity that describes the force a positive test charge would experience at any point in space.
Direction convention
E points AWAY from positive charges and TOWARD negative charges. This follows from the definition using a positive test
Rules for drawing field lines
1. Lines begin on positive charges; terminate on negative charges (or extend to infinity for isolated charges)
Single positive charge
Lines radiate outward in all directions Single negative charge: lines converge inward from all directions
Result
The Coulomb force becomes effectively short-range in biological systems because of this screening.
Cell membrane function
Ion movement through cell membranes drives nerve impulses. The membrane carries opposite charges on inner and outer surf
Wound healing connection
Research shows cells release calcium ions immediately upon damage, triggering an electrochemical response that initiates
WHY
If any field existed inside, free electrons would feel a force and keep moving. They stop only when they've redistribute
LASER PRINTER
Same xerographic process; laser beam replaces light projection for higher precision imaging.
Fundamental charge
E = 1.60 x 10^-19 C