Search Results

Core Info and Definitions A relational database contains tables, making use of relations between them to store data with minimal data redundancy. Normalisation is a process used to come up with the best possible database design by following a set of formal r...

Modelling Core info and definitions When creating a database, you must identify the entities. An entity is a "category of object, person, event or thing of interest to an organisation about which data to be recorded". These entities are presented as tables. ...

Xray production Electrons are emitted into a vacuum tube via thermionic emission. An external power supply produces a massive p.d. between the anode and cathode, causing the electrons to be rapidly accelerated in this high-voltage electric field. Then they are...

Core Info and Definitions A capacitor is a circuit component that stores charge in a circuit by separating equal and opposite charges onto two electrical conductors (plates) with an insulator in between them.  Capacitance, C, defines the quantity of charge Q...

Definitions and Core Info An electric field is a region around a body in which other charged bodies will feel a force. The direction of the field is the direction of the force experienced by a positive test charge. ... where F is the size of the electrical...

Definitions and Core Info A magnetic field is a field in which a charged particle experiences a force. Its direction is determined by the force experienced by a positive test charge. Field Lines Magnetic Force Flemings' left hand rule: Thumb: Thrust (...

Key info and definitions Electric Circuit Components Junction of conductors: Allows current to split; resistance is typically low but increases with temperature. Conductors crossing (no connection): Allows current to flow across a circuit without connec...

Potential Difference and EMF Potential difference is the energy transferred per unit charge from electrical energy to other forms, such as light and sound. EMF is the energy transferred from an energy source, such as chemical energy in cells, to electrical...

Kirchoff's Laws The sum of currents entering a junction in a circuit is equal to the sum of currents exiting this junction. This ensures conservation of charge. The sum of emfs in a loop of a circuit is equal to the sum of potential differences of all comp...

Wave Motion Waves transfer energy from one place to another without any net transfer of matter. These can be longitudinal or transverse: Longitudinal Maxima at compressions and minima at rarefactions. Particles move parallel to the direction of e...

Photons A quantum (plural: quanta) is a small discrete unit of energy. A photon is a quantum of EM radiation. Photon energies are always emitted in multiples of the Planck constant, h = 6.63e-34. Photon energy in joules is determined using: These energie...

Storing "lists" of data A static data structure is fixed in size. A dynamic data structure has a variable size. It does this with the use of a heap, which is a portion of memory from which space is automatically allocated and deallocated as required. Arrays...

The Nuclear Atom The alpha particle scattering experiment involved the firing of alpha particles at a thin sheet of gold foil. Due to the old belief in the plum-pudding model for the atom, it was expected that the alpha particles would pass straight through th...

Abstraction Thinking Ahead Thinking Procedurally Thinking Logically & Concurrently Backtracking Backtracking is when different sequences of actions are tried to obtain a solution. If one path doesn't work, you "backtrack" to the last known working point. An ex...

The Internet The internet is a network of networks set up to allow computers to communicate with each other globally. It is accessed via Internet Service Providers (ISPs), which usually provide routers for families and businesses to access the internet. URLs U...

A-Level Physics Practicals This document covers the core practical procedures across the A-Level Physics course, organized by module Module 3: Mechanics 1. Investigating Motion and Collisions Focuses on verifying momentum conservation or investigating the rel...

Threats Viruses A virus is a piece of malicious software that has the ability to self-replicate. It exists in a host file, usually an executable file of some sort. It inserts its malicious code in other executable files to spread. A virus can be: spyware, whic...

The Processor The processor refers to any electronic component capable of performing mathematical and logical operations. While the CPU (central processing unit) is the primary general purpose processor responsible for managing the system, other specialised pr...