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Electricity, Waves & Quantum Physics Definitions
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Gravity
Key Concepts:
Terms in this set (44)
electric current
The net rate of flow of charged particles.
one coulomb
The amount of charge which lows past a point in 1 second when there is a current of 1A.
elementary charge e
The charge carried by one proton.
Kirchhoff's first law
The sum of the currents entering any junction in a circuit is equal to the sum of the currents leaving the junction.
mean drift velocity
The average displacement per second of charged particles along the length of a conductor.
potential difference
The energy transferred per unit charge when electrical energy is converted into another form of energy.
electromotive force
The energy transferred per unit charge when another form of energy is converted into electrical energy.
one volt
1 joule per coulomb.
resistance
The potential difference across the component divided by the current passing through it.
Ohm's law
The electric current through a conductor is proportional tot he potential difference across it, provided physical conditions such as temperature remain constant.
resistivity
The product of the resistance and the cross-sectional area of a wire divided by its length.
power
The rate of energy transfer.
1 kilowatt-hour
The energy transferred in one hour by a 1000W device and is equal to 3.6MJ.
Kirchhoff's second law
The sum of the e.m.f.s around any loop in a circuit is equal to the sum of the p.d.s around the loop.
potential divider
Reduces the output voltage of an e.m.f. The ouput voltage is shared between two resistors in proportion to their resistance.
longitudinal wave
The medium oscillates in a direction parallel to the direction of energy transfer.
transverse wave
The medium oscillates in a direction perpendicular to the direction of energy transfer.
displacement
The distance of a point from the equilibrium position.
amplitude
The maximum displacement from the equilibrium position.
wavelength
The distance from any point of a wave to the next identical point with the same phase.
period
The time taken for one complete oscillation.
frequency
The number of oscillations per unit time.
wave speed
The distance travelled by the wave per unit time.
intensity
The energy transmitted per unit area per unit time at right angles to the direction of the velocity.
polarised wave
Oscillates in only one direction which is perpendicular to the direction of energy transfer. It must be a transverse wave.
path difference
The difference in the distances travelled by two waves from coherent sources at a particular point.
phase difference
The difference by which the oscillation at one point on a wave leads or lags that at another point of the wave as a fraction of the wavelength expressed as an angle in degrees or radians.
refractive index n
(speed of light in a vacuum c)/(speed of light in the medium v)
critical angle
The angle of incidence that gives an angle of refraction of 90. sin C = 1/n
principle of superposition of waves
When two or more waves meet at a point, the resultant displacement is the sum of the displacements of the individual waves.
interference
The superposition of two coherent waves with the resultant displacement equal to the sum of the individual displacements.
diffraction
The spreading out of wave paths when a wave passes through a gap or around an obstacle.
coherent waves
Have a constant phase difference.
progressive wave
Carries energy through a medium or vacuum as a result of oscillations.
stationary wave
An oscillation in which energy is trapped in fixed positions.
node
A point on a stationary wave that always has zero amplitude.
antinode
A point on a stationary wave that has maximum amplitude.
fundamental mode
The stationary wave with a single antinode. It is the minimum frequency of a standing wave for a given system.
harmonics
Whole number multiples of the fundamental frequency of a stationary wave.
photon
A quantum of energy of electromagnetic radiation.
one electron volt
The energy transferred when an electron is accelerated through a potential difference of one volt.
photoelectric effect
The emission of electrons from the surface of a metal when photons with sufficient energy strike it.
work function
The minimum energy required to release an electron from the surface of the metal.
threshold frequency
The lowest frequency of electromagnetic radiation that will cause the emission of photoelectrons from the surface of a metal.
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