# G482 key words and definition

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Resistance
p.d./current
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Kirchhoff’s second law
(sum of) e.m.f.s = sum /total of p.d.s/sum of voltages (in a loop).
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Mean Drift Velocity
the average displacement/distance travelled of the electrons along the wire per second. (Over time) they move slowly in one direction through the metal lattice (when there is a p.d. across the wire) (because) they collide constantly
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Resistivity
resistance time the cross-sectional area, divided by the length (ρ = RA/l).
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Wavelength
distance between (neighbouring) identical points/points with same phase (on the wave).
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Frequency
number of waves passing a point /cycles/vibrations (at a point) per unit time/second.
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Speed (of a wave)
distance travelled by the wave (energy) per unit time/second
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infra red is part of the e-m spectrum longer λ than the visible light (10-5  7.5x10-7).
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Interference
when (two) waves interact (at a point) there is a change in overall displacement.
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Coherence
constant phase difference/relationship (between the waves).
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Diffraction
paths spread out after passing through a gap or around an obstacle.
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Kilowatt-hour
(a unit of) energy equal to 3.6 MJ.
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Intensity
intensity is the (incident) energy per unit area per second.
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Line Spectrum
light emitted from (excited isolated) atoms produces a line spectrum a series of (sharp/bright/coloured) lines against a dark background.
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Electronvolt
an eV is the energy acquired by an electron accelerated/moves through a p.d. of 1 V (1 eV = 1.6 x 10-19J ).
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de Broglie Wavelength
Electrons are observed to behave as waves/show wavelike properties where the electron wavelength depends on its speed/momentum.
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Photon
a particle of (e-m) energy/light.
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Continuous Spectrum
all wavelengths/frequencies are present (in the radiation).
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Potential Difference
energy transfer per unit charge from electrical to other forms.
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Work Function
the minimum energy (required) to release an electron (from the surface of the metal).
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Plane Polarised Wave
a transverse wave in the plane normal to the direction of (energy) propagation. Oscillations confined to a single plane (containing the direction of propagation).
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e.m.f
energy transferred from source/changed from some form to electrical energy per unit charge.
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Progressive Wave
is a transfer of energy as a result of oscillations (of the medium through which energy is travelling).
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Power
Work done/energy transfer(red) per unit time
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Displacement
(any) distance moved from equilibrium of a point/particle on a wave.
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Amplitude
maximum displacement (caused by wave motion).
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Phase difference
between two points on the same wave/waves of the same frequency, how far through the cycle one point is compared to the other
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## Other cards in this set

### Card 2

#### Front

(sum of) e.m.f.s = sum /total of p.d.s/sum of voltages (in a loop).

#### Back

Kirchhoff’s second law

### Card 3

#### Front

the average displacement/distance travelled of the electrons along the wire per second. (Over time) they move slowly in one direction through the metal lattice (when there is a p.d. across the wire) (because) they collide constantly

### Card 4

#### Front

resistance time the cross-sectional area, divided by the length (ρ = RA/l).

### Card 5

#### Front

distance between (neighbouring) identical points/points with same phase (on the wave).