Phys2 Cheat Sheet by userunkn0wn

Conduc­tors: A material that allows the flow of electrical charge. Good conductors have a larger amount of free charge carriers to carry a current.

Conven­tional Current: The flow from positive to negative, used to describe the direction of current in a circuit.

Electric Current: The rate of flow of charge in a circuit.

Electron Flow: The opposite direction to conven­tional current flow. Electrons flow from negative to positive.

Insula­tors: A material that has no free charge carriers and so doesn’t allow the flow of electrical charge.

Mean Drift Velocity: The average velocity of an electron passing through an object. It is propor­tional to the current, and inversely propor­tional to the number of charge carriers and the cross-­sec­tional area of the object.

Semico­ndu­ctors: A material that has the ability to change its number of charge carriers, and so its ability to conduct electr­icity. Light dependent resistors and thermi­stors are both examples.

Amplitude: A wave’s maximum displa­cement from its equili­brium position.

Coherence: Waves with the same frequency and constant phase difference

Critical Angle: The angle of incidence that results in an angle of refraction of exactly 90o . It is when the refracted ray travels along the boundary line.

Diffra­ction: The spreading of waves as they pass through a gap of a similar magnitude to their wavele­ngth.

Electr­oma­gnetic Spectrum: The spectrum of electr­oma­gnetic waves, consisting of Gamma Rays, X-Rays, Ultrav­iolet, Visible Light, Infrared, Microwaves and Radiow­aves.

Frequency: The number of waves that pass a point in a unit time period. It is the inverse of the time period.

Intensity: The power transf­erred per unit area. It is propor­tional to the square of a wave’s amplitude.

Longit­udinal Waves: A wave with oscill­ations that are parallel to the direction of energy propag­ation. Sound waves are an example of a longit­udinal wave. They cannot travel through a vacuum.

Oscill­oscope: A device used to display and analyse waveforms.

Period: The time taken for a wave to complete one full cycle

Polari­sation: The restri­ction of a wave so that it can only oscillate in a single plane. This can only occur for transverse waves.

Reflec­tion: The bouncing of a wave at a boundary. The angle of incidence will equal to the angle of reflec­tion.

Refractive Index: A material property that is equal to the ratio between the speed of light in a vacuum, and the speed of light in a given material.

Superp­osi­tion: When two waves meet at the same point in space their displa­cements combine and the total displa­cement at that point becomes the sum of the individual displa­cements at that point

Transverse Waves: A wave with oscill­ations that are perpen­dicular to the direction of energy propag­ation. Electr­oma­gnetic waves are examples of transverse waves

Wavele­ngth: The distance between two identical positions on two adjacent waves. It is commonly measured from peak to peak or trough to trough.

Diode: A component that allows current through in one direction only. In the correct direction, diodes have a threshold voltage (typically 0.6 V) above which current can flow

Filament Lamp: A bulb consisting of a metal filament, that heats up and glows to produce light. As the filament increases in temper­ature, its resistance increases since the metal ions vibrate more and make it harder for the charge carriers to pass through.

Kilowa­tt-­Hour: A unit of electrical energy. It is usually used to measure domestic power consum­ption.

Ohm: The unit of resist­ance.

Ohm’s Law: The current and potential difference through an ohmic conductor held under constant physical conditions are directly propor­tional, with the constant of propor­tio­nality being resist­ance.

Power: The rate of energy transfer in a circuit. It can be calculated as the product of the current and the potential difference between two points. It is measured in Watts.

Resist­ivity: A measure of how difficult it is for charge to travel through a material. It is propor­tional to the object’s resistance and cross-­sec­tional area, and inversely propor­tional to the object’s length. It is measured in Ohm metres

Volt: The unit of potential differ­ence.

Conser­vation of Energy: Energy cannot be created or destroyed - it can only be transf­erred into different forms.

Kirchh­off's Second Law: A conseq­uence of the conser­vation of energy. The sum of the voltages in any closed loop must equal zero

Parallel Circuit: Components are said to be connected in parallel when they are connected across each other (separate loops).

Resistors in Parallel: The potential difference across resistors connected in parallel is identical for each resistor. The current is split between the resistors. The total resistance is equal to the inverse of the sum of the inverses of the resist­ances of the resistors

Sensor Circuits: A circuit that reacts to external condit­ions. They commonly involve a semico­nductor connected in a potential divider arrang­ement.

Terminal PD: The potential difference across the terminals of a power source. It is equal to the source’s emf minus any voltage drop over the source’s internal resist­ance.