Physics Compendium for Biomedical Engineering

Flashcards on Physics Concepts for Biomedical Engineering

Physical Quantity

A measurable aspect of a physical phenomenon, expressible as a numerical value with a unit.

Fundamental Quantities

Length (m), Mass (kg), Time (s), Temperature (K), Electric current (A).

Derived Quantities

Velocity (m/s), Force (N), Energy (J), Pressure (Pa).

Physical Model

A simplified but effective representation of how nature behaves.

Scalars

Mass, Temperature, Energy.

Vectors

Force, Acceleration, Electric field.

Bohr Model

Electrons orbit the nucleus in discrete energy levels. Jumping between them emits or absorbs photons.

Quantum Model

Orbitals describe probability clouds — electrons are smeared, not points.

Conductor

Valence and conduction bands overlap.

Insulator

Large band gap.

Semiconductor

Small band gap, tunable with doping.

Absorption

Electron jumps up a level by absorbing energy.

Emission

Falls down a level, emits a photon.

Conductors

Free electrons (e.g., Cu, Al).

Insulators

Bound electrons (e.g., glass).

Semiconductors

Switch from insulators to conductors via temperature or doping.

n-type Semiconductor

Extra electrons (from dopants like P).

p-type Semiconductor

Missing electrons or “holes” (from B).

Molecular Model of Gases

Kinetic theory describes gases as countless moving particles: Pressure ∝ collision frequency × momentum

Temperature

Average kinetic energy of molecules.

Pressure

Force molecules exert on container walls per unit area.

Solid

Fixed shape, low energy.

Liquid

Takes container shape, higher energy.

Gas

Free motion, fills volume.

Plasma

Ionized gas with extreme energy.

Zeroth Law of Thermodynamics

A = B and B = C implies A = C — basis of thermometers.

First Law of Thermodynamics

Energy conservation. ∆U = Q + W

Second Law of Thermodynamics

Heat flows spontaneously from hot to cold; entropy increases.

Third Law of Thermodynamics

You can’t reach 0 K in finite steps.

Electric Field

A region where a charge feels a force. Arrows point from + to -.

Magnetic Field

Magnetic field affects moving charges only.

Conclusions from Maxwell

EM waves are self-propagating fields.

Transverse waves

E⃗ and B⃗ are perpendicular to each other and to propagation direction.

Polarization

Direction of electric field oscillation.

Energy Density

EM radiation carries energy.

Intensity

Higher intensity gives more photons.

Diffraction

Phenomenon showing wave nature of light, resulting in constructive and destructive interference.

Index of Refraction

n = c/v

Refraction

Speed changes and bends toward normal when entering higher n.