Physics: Electromagnetism and Classical Mechanics

• Physics explores matter, energy, and their interactions.
• Physics aims to elucidate the universe's fundamental laws.
• It spans from subatomic particles to the cosmos' expansive structure.

Electromagnetism

• Electromagnetism studies interactions between electric charges and magnetic moments.
• Maxwell's equations, a set of four differential equations, describe electromagnetism.
• Electromagnetism combines electricity and magnetism into a single electromagnetic force.
• Key electromagnetic concepts include electric charge, electric fields, magnetic fields, and electromagnetic waves.
• In a vacuum, electromagnetic waves propagate at the speed of light.
• Light exists as an electromagnetic wave.
• Radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays exemplify electromagnetic phenomena.
• Electromagnetism finds use in electric generators, motors, communications, and medical imaging.

Classical Mechanics

• Classical mechanics details the motion of macroscopic objects.
• Newton's laws of motion are the basis:
  • First law (Inertia): Objects maintain their state of rest or constant motion unless acted upon by a net force.
  • Second law: Force equals the rate of momentum change, simplified to F=ma when mass is constant.
  • Third law: Every action has an equal and opposite reaction.
• Displacement, velocity, acceleration, force, mass, momentum, energy, and work are key concepts.
• Classical mechanics is deterministic; knowing initial conditions allows for predicting future behavior.
• It accurately portrays motion at speeds far below light speed and for objects much larger than atoms.

Thermodynamics

• Thermodynamics studies heat, work, and energy transfer.
• Its four laws are:
  • Zeroth law: Systems in thermal equilibrium with a third system are in equilibrium with each other.
  • First law: Energy conservation; internal energy change equals heat added minus work done.
  • Second law: Entropy in an isolated system increases over time.
  • Third law: As temperature nears absolute zero, entropy approaches a constant value.
• Temperature, heat, internal energy, entropy, and enthalpy are key concepts.
• Thermodynamics finds application in engines, refrigerators, and energy conversion devices.
• Statistical mechanics interprets thermodynamics via the behavior of numerous particles.

Quantum Mechanics

• Quantum mechanics describes matter's behavior at atomic and subatomic scales.
• Energy, momentum, angular momentum, and related quantities are quantized, existing in discrete values.
• Wave-particle duality, the uncertainty principle, superposition, and entanglement are key concepts.
• Wave-particle duality: Particles behave as both waves and particles.
• The uncertainty principle: Limits exist on the precision of knowing certain pairs of physical quantities like position and momentum.
• Superposition: Quantum systems exist as combinations of multiple states simultaneously.
• Entanglement: Linked quantum systems share the same fate regardless of distance.
• Quantum mechanics explains the behavior of atoms, molecules, and solids.
• Technologies such as lasers, transistors, and MRI rely on it.

Relativity

• Relativity is a theory about space, time, and gravity.
• Its two main branches are:
  • Special relativity: Examines space-time relations for objects at constant velocity. It assumes that physics laws remain consistent for observers in uniform motion and that light speed in a vacuum is constant, regardless of the light source's motion.
  • General relativity: Describes gravity for accelerating objects, depicting it as spacetime curvature due to mass and energy.
• Spacetime, time dilation, length contraction, mass-energy equivalence (E=mc^2), and gravitational waves are key concepts.
• Time dilation: Time slows for objects at high speeds relative to a stationary observer.
• Length contraction: Objects at high speeds appear shorter in their direction of motion to a stationary observer.
• General relativity predicts black holes: spacetime regions with gravity strong enough to prevent anything, even light, from escaping.
• The bending of light around massive objects and the existence of gravitational waves provide experimental confirmation.

Space

• Space is the limitless three-dimensional realm housing objects and events with relative positioning.
• Space refers to what exists beyond Earth's atmosphere.
• Celestial objects (stars, planets, galaxies), distances, time, and physical laws governing the universe are key concepts.
• Cosmology studies the universe's origin, evolution, and structure.
• Astronomy studies celestial objects and phenomena.
• Astrophysics uses physics to examine celestial objects and phenomena.
• Space exploration uses spacecraft for space study and exploration.
• The universe contains billions of galaxies, each with billions of stars.
• The universe is expanding.