Electromagnetism Fundamentals: Charges, Fields, and Circuits
Coulomb’s Law
The magnitude of each electrical force between two stationary point charges is directly proportional to the product of the magnitudes of both charges and inversely proportional to the square of the distance between them.
Coulomb’s law is valid only in stationary conditions, i.e., when there is no charge movement or when the movement occurs at low speeds and in uniform rectilinear trajectories. This is why it is called electrostatic force.
In mathematical terms, the magnitude 
force that
Human Eye Anatomy, Myopia, and Hyperopia: Vision Explained
Eye Anatomy
The human eye, the organ of vision, is an optical system producing images on the retina. This inner eye surface, light-sensitive and roughly spherical (about 25 mm in diameter), displays real, inverted images. Key parts include:
- Sclera: The external, white, opaque, and resistant membrane. In front, it becomes the transparent cornea.
- Cornea: The transparent front part of the eye, allowing light entry.
- Choroid: A membrane lining the eye’s interior (except the cornea), absorbing light.
- Aqueous
Atomic Structure and Wave Phenomena
Item 8: Atomic Structure
Dalton’s Atomic Theory
- Matter consists of individual atoms.
- Atoms are unchanged in chemical reactions.
- Atoms of the same element are identical.
- Atoms of different elements have different masses and chemical properties.
- Chemical compounds are formed by combining two or more atoms of different elements.
- When two or more atoms of different elements combine to form the same compound, they do so in simple whole-number ratios.
- In chemical reactions, atoms are not created nor destroyed,
Evolution of Astronomical Models and Gravity Concepts
Ptolemy’s Geocentric Models
Alexandra Ptolemy (86-165) established a geometric model where the Earth is fixed, and planets revolve around it. The Sun and Moon orbit Earth in circular paths, while other planets follow complex orbits. Planets move in small circles (epicycles) whose centers trace larger circles around Earth. A field of stars also revolves around Earth.
Heliocentric Models
Aristarchus’ Model
Aristarchus of Samos (310-230 BC) proposed a heliocentric model with the Sun at the center, and
Read MorePhysics Essentials: Vibrations, Waves, Gravity, Fields, Optics
Vibratory Motion (MAS) – Radians
X(t) = a sin (wt + fi), A = xmax
w = 2π / T = 2πnu, nu = 1/T = 1/nu
vtransversal = dx / dt
a = –w2 · x
x = Acoswt = acos (wt + π/2)
v = Awcos (wt + fi), vmax = Aw
v = ±w · √(A2–x2)
F = –kx, K = Mw2-√ w = k / m (kN/m)
Simple Pendulum – Theta
θ = s / l
T = 2π · √(L / g)
s = θ x L
cos θ = Lh / L
w = √(g / L)
θ(t) = θm sin (wt + fi) – fi then removed
Energy of an Oscillator
Ec = 1/2mv2
Ep = Ep(x), W = Ep
For a Spring
Ep = 1/2kx2
Ec = 1/2mv2
Et = Ep + Ec = constant
In the
Read MoreFaraday’s Experiments and Electromagnetic Induction
Faraday’s Experiences
The English physicist and chemist M. Faraday experimentally obtained an electrical current from magnetism in 1831. These are his stories:
- First experience: moving a magnet inside a coil. If approaching the magnet to a coil, an induced current occurs during the movement of the magnet. The direction of the induced current is reversed if the magnet moves away. With a fixed coil and magnet, no induced current is observed. The same results are obtained if we keep the magnet fixed