OCR G482 Definitions

Definitions of all important units/words needed in the OCR G482 exam.

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Physics Definitions - G482
Volt ­ Unit for voltage - One Joule per Coulomb (JC-1)
Amp ­ Unit for current - One Coulomb per Second (CS-1)
Watt ­ Unit for Power ­ One Joule per Second (JS-1)
Charge ­ The charge of electricity measured in Coulombs (Q=It)
Resistance ­ A property of a component that regulates to electrical current through it
(Measured in Ohms )
Conventional Current ­ A model used to describe the movement of charge in a circuit ­
(from + to -)
Electron Flow ­ The movement of electrons from - to + (opposite to conventional
Electrical Current ­ A flow of charge (measured in Amps)
Number Density ­ The number of conduction electrons in a conductor
Drift Velocity ­ The average velocity of an electron as it travels through a wire due to a
Potential Difference (p.d.) ­ The electrical energy transferred into another type of
energy per unit charge (Measured in Volts)
Electromotive Force (E.m.f.) ­ The energy transferred from one form of energy into
electrical energy per unit charge (Measured in
LED ­ A component that only allows electric current to pass in one direction and emits
light h when a potential difference is across it
Thermistor ­ A component where as temperature increases, resistance decreases
Light Dependent Resistor (LDR) ­ A component where low light means high resistance
Ohms Law ­The current through a conductor is proportional to the potential difference
across it, at constant temperature

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Kirchhoff's 1st Law ­The sum of the currents entering any junction is always equal to the
sum of currents leaving the junction (conservation of charge)
Kirchhoff's 2nd Law ­ The sum of the e.m.f.'s is equal to the sum of the p.d.…read more

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Refraction ­ When waves change direction due to travelling from one medium to
another and changing speed
Diffraction ­ When a wave spreads out after passing through a gap
Quantum Physics
Quantum ­ A discrete, indivisible quantity
Photon ­ A quantum of light
Electron Volt ­ The energy change of an electron when it moves through a potential
difference of 1 volt (1.…read more

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