Branches of Physics

Mechanics: study of motion, forces, and energy
Thermodynamics: study of heat, temperature, and energy transfer
Electromagnetism: study of electricity, magnetism, and electromagnetic waves
Optics: study of light, its properties, and behavior
Quantum Mechanics: study of the behavior of matter and energy at the atomic and subatomic level
Relativity: study of space and time, including special relativity and general relativity

Motion:
- Displacement: change in position
- Velocity: rate of change of displacement
- Acceleration: rate of change of velocity
Forces:
- Gravitational force: force of attraction between two objects
- Frictional force: force opposing motion
- Normal force: force exerted by a surface on an object
Energy:
- Kinetic energy: energy of motion
- Potential energy: energy of position or state
- Conservation of energy: energy cannot be created or destroyed, only converted

Newton's Laws:
1. First law: an object at rest will remain at rest, and an object in motion will continue to move, unless acted upon by an external force
2. Second law: force is equal to the rate of change of momentum
3. Third law: every action has an equal and opposite reaction
Laws of Thermodynamics:
1. Zeroth law: if two systems are in thermal equilibrium with a third system, they are also in thermal equilibrium with each other
2. First law: energy cannot be created or destroyed, only converted
3. Second law: entropy always increases in a closed system
4. Third law: as the temperature of a system approaches absolute zero, the entropy of the system approaches a minimum value

Isaac Newton: developed laws of motion and universal gravitation
Albert Einstein: developed theory of relativity and photoelectric effect
Marie Curie: discovered radioactive elements and developed theory of radioactivity
Erwin Schrödinger: developed theory of quantum mechanics
Niels Bohr: developed model of the atom and principle of complementarity

Study of motion, forces, and energy is Mechanics
Thermodynamics is the study of heat, temperature, and energy transfer
Electromagnetism is the study of electricity, magnetism, and electromagnetic waves
Optics is the study of light, its properties, and behavior
Quantum Mechanics is the study of the behavior of matter and energy at the atomic and subatomic level
Relativity is the study of space and time, including special relativity and general relativity

Kinetic energy is the energy of motion
Potential energy is the energy of position or state
Conservation of energy states that energy cannot be created or destroyed, only converted

An object at rest will remain at rest, and an object in motion will continue to move, unless acted upon by an external force (First law)
Force is equal to the rate of change of momentum (Second law)
Every action has an equal and opposite reaction (Third law)

If two systems are in thermal equilibrium with a third system, they are also in thermal equilibrium with each other (Zeroth law)
Energy cannot be created or destroyed, only converted (First law)
Entropy always increases in a closed system (Second law)
As the temperature of a system approaches absolute zero, the entropy of the system approaches a minimum value (Third law)

Isaac Newton developed laws of motion and universal gravitation
Albert Einstein developed theory of relativity and photoelectric effect
Marie Curie discovered radioactive elements and developed theory of radioactivity
Erwin Schrödinger developed theory of quantum mechanics
Niels Bohr developed model of the atom and principle of complementarity

Kirchhoff's Current Law states that the sum of all currents entering a node in an electrical circuit is equal to the sum of all currents leaving the node.

ΣI_in = ΣI_out, where I_in is the sum of all currents entering the node and I_out is the sum of all currents leaving the node.

Consider a node with three wires attached, carrying currents I1, I2, and I3.
If I1 and I2 are entering the node, and I3 is leaving the node, KCL states: I1 + I2 = I3.