# Shared Flashcard Set

## Details

Physics G482 Revision Cards
Revision Cards set for G482 Key Terms
44
Physics
Not Applicable
06/07/2014

Term
 Current
Definition
 The flow of charge over time, between two points. Measured in Amperes, (A) and 1A of current is equivalent to 1Cs-1
Term
 Charge
Definition
 The amount of charge that flows past a point with 1A current in 1 second. Measured in Coulombs (C)
Term
 Resistance
Definition
 The ratio of voltage to current through a component
Term
 Ohm's Law
Definition
 For a metallic conductor, at constant temperature, the current in the conductor is directly proportional to the potential difference across its ends
Term
 Resistivity
Definition
 The resistance of a material, multiplied by its cross sectional area, per unit length
Term
 Thermistor
Definition
 Temperature dependant resistors:PTC - Positive temperature coefficientNTC - Negative temperature coefficient
Term
 LED
Definition
 Light Emitting Diodes - Semiconductors & only allow current through in one direction (diode)
Term
 Voltage / Potential Difference
Definition
 The energy transferred from charge in a circuit to a component (energy transferred per unit charge - V=W/Q)
Term
 Electromotive Force
Definition
 E.m.f. - Energy transferred from supply (battery/cell/supply) to a circuit (energy transferred per unit charge - E=W/Q)
Term
 Power
Definition
 The rate of transfer of energy - Measured in Watts (J/s)
Term
 Watt
Definition
 Unit of Power - Equivalent to the transfer of one Joule per Second (1W=1J/1s)
Term
 Energy
Definition
 Equal to the current multiplied by the voltage, multiplied by the time
Term
 1KWh
Definition
 One Kilo-Watt Hour - equivalent to the energy transferred to a 1KW device operating for one hour
Term
 Internal Resistance
Definition
 The resistance produced inside a supply of e.m.f. - due to chemicals (cell), wires or components (supply) in the circuit
Term
 Terminal p.d.
Definition
 This is the potential difference across the two terminals of the supply
Term
 'Lost Volts'
Definition
 This is the difference in volts, between the e.m.f. and the Terminal p.d.
Term
 Kirchhoff’s First Law
Definition
 The sum of any current entering a junction is equal to the sum of the current leaving the junction (conservation of charge)
Term
 Kirchhoff’s Second Law
Definition
 The Sum of the e.m.f. around a circuit loop is equal to the sum of the p.d.s around the same loop (conservation of energy)
Term
 Displacement
Definition
 The distance from the point on a wave to the line of undisturbed positions
Term
 Amplitude
Definition
 The maximum displacement of any point on a wave - proportional to the volume of sound waves
Term
 Wavelength
Definition
 The distance from any point on a wave to the next exactly similar point - distance of one full cycle)
Term
 Frequency
Definition
 The number of complete oscillations per second - Hz
Term
 Intensity
Definition
 The rate of energy transmitted per unit area, perpendicular to the wave velocity
Term
 Wave Speed
Definition
 The speed at which the energy is transmitted
Term
 Reflection
Definition
 Occurs where waves impact an impermeable barrier & change direction and become anti-phase to the incident wave
Term
 Progressive wave
Definition
 A wave that has wave speed and therefore carries energy from one place to another
Term
 Malus's Law
Definition
 This states that the Intensity (& therefore Amplitude) of a resultant wave after passing through a polarising filter is proportional to the cosine of the incident angle to the direction of the polarising filter
Term
 Principle of superposition of waves
Definition
 This states that when two waves interfere with each other, the resultant wave is proportional to the algebraic sum of the two waves’ displacement
Term
 Constructive Interference
Definition
 This occurs when the algebraic sum of the displacements produces an increased amplitude resultant wave
Term
 Destructive Interference
Definition
 This occurs when the algebraic sum of the displacements produces a reduced amplitude resultant wave
Term
 Diffraction
Definition
 This is the spreading out of a wave as it passes through a gap or around an edge and is proportional to the difference of the aperture and the wavelength
Term
 Stationary Waves
Definition
 These are waves that are reflected back onto themselves and are in anti-phase (180° out of phase). However, due to their opposite direction of movement, they combine constructively and destructively at the same point, varying with time
Term
 Node
Definition
 Point of zero amplitude
Term
 Anti-node
Definition
 Point of maximum amplitude which oscillates.
Term
 Fundamental Frequency
Definition
 The minimum frequency of a standing wavefor a given system or arrangement
Term
 Photoelectric effect
Definition
 This is the effect of exposing a charged zinc plate attached to an electroscope to Ultraviolet light. This proves, as the electroscope reduces in reading, that the light must be discharging the plate. This is evidence for the particle model of light (photons), contradicting the wave model we have used before
Term
 Threshold Frequency
Definition
 The minimum frequency required to release electrons from the surface of a metal
Term
 Work Function
Definition
 The minimum amount of energy required by an electron to escape a metal’s surface
Term
 KE Max
Definition
 This is the maximum kinetic energy of an electron after it escapes the surface of the metal
Term
 De Broglie wavelength
Definition
 This relates a particle’s momentum to its wavelength
Term
 White Light
Definition
 This is light that comprises of the full spectrum of visible light
Term
 Emission line spectra
Definition
 This is the spectra emitted (given off) by a body when white light is passes through it and then is re-emitted. The black lines show the spectra that hasn’t been absorbed & then re-emitted. This occurs for isolated atoms (body of gas) – Where the electrical forces between atoms are negligible
Term
 Absorption line spectra
Definition
 This is the spectra emitted by white light that has passed through a body & is not interfered with. The black lines show the spectra that have been absorbed. These occur when EM radiation is absorbed by isolated atoms (body of gas). An electron absorbs a photon of the correct energy to allow it to make a transition to a higher energy level
Term
 Energy levels
Definition
 These are the levels of energy that an electron can have inside an atom
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