Module 2 definitions Flashcards
Electric current
The rate of flow of charge
Quantised
The availability of some quantities such as energy or charge
Conventional current
Conventional current travel from positive to negative- it is the direction in which positive charge would travel
Conservation of charge
Electric charge cannot be created or destroyed. The total charge for any interaction must be the same before and after.
Kirchhoff first law
At any point in an electrical circuit, the sum of current into that point is equal to the sum of currents out of that point, electrical charge is conserved.
Number density
The number of free electrons per cubic metre of a material
Semiconductor
A material with a lower number density than a typical conductor eg silicon
Mean drift velocity
The average velocity of electrons as they move through a wire.
Potential difference
The energy transferred from electrical energy to other forms (heat light) per unit charge.
Electromotive force
The energy transferred from chemical to electrical energy per unit charge.
Ohm’s law
The potential difference across a conductor us directly proportional to the current in the component as long as its temperature remains constant
Ohmic conductor
A conductor that obeys ohms law
Diode
a semiconductor that allows current only in one particular direction
Threshold pd
The minimum potential difference at which a diode begins to conduct
Resistivity
A property of material
The product of the resistance of a component made of that material and its cross sectional area divide by its length.
Kilowatt hour
Kirchhoff second law
In a close loop of an electrical circuit the sum of emf is equal to the sim of pds
Lost volts
The potential difference across the internal resistor of a source of emf
m
Terminal pd
The potential difference across a electrical power source- when there is no current this is equal to the emf of the source but if there is current the source is equal to the emf minus the lost volts.
Potential dividers
An electrical circuit designed to divide the potential difference across two or more components in order to produce a specific output.
Longitudinal waves
Oscillations are parallel to the direction of the wave travel
Equilibrium position
The resting position if waves or particles in an oscillation
Wavelength
The minimum direction between two points oscillating in phase.
Wave speed
The distance travelled by the wave per unit time.
Time period
Phase difference
The difference between the displacement of particles along a wave same or different waves.
Reflection
The change in direction of a wave at a boundary between two different media, so that the wave remains in the original medium
Refraction
The change in direction of a wave as it changes speed when it passes from one medium to another
Law of reflection
The angle of incidence is equal to the angle of reflection
Diffraction
The phenomenon waves passing through a gap or around an obstacle spread out.
Polarisation
The phenomenon in which the oscillation of a transverse wave are limited to only one plane.
Intensity
The radiant power passing through a surface per unit area.
Refractive index
Total internal reflection
The reflection of all light hitting a boundary between two media back into the original medium when light is travelling the medium with the higher refractive index and the incidence angle at the boundary is greater than the critical angle.
Critical angle
The angle of incidence at the boundary between two media that will produce an angle of refraction of 90degrees.
Interference
Superposition of two progressive waves from coherent sources to produce a resultant wave with the displacement equal to the sum of individual displacement from the two waves
Principle of superposition
When two similar waves meet at a point the resultant displacement at that point is equal to the sum of the displacement of the individual waves.
Constructive interference
Superposition of two waves in phase so that the resultant wave has a greater amplitude than the original waves.
Destructive interference
Superposition of two waves in anti phase so that the waves cancel each other out and the resultant waves has smaller amplitude than the original wave
Path difference
The difference in the distance travelled by two waves from their source to a specific point.
Monochromatic
Light of a single frequency.
Node
For a stationary wave a point where the amplitude is always zero.
Antinode
Stationary wave
A wave that remains in a constant position with no net transfer of energy and is characterised but its nodes and antinodes.
Fundamental frequency
The lowest frequency at which an object can vibrate.
Photons
A quantum of electromagnetic energy
Electronvolt
The energy transferred to or from an electron when its passes through a potential difference of 1 volt.
Photoelectric effect
The emission of photoelectrons from a metal surface when electromagnetic radiation above the threshold frequency is incident on the metal.
Threshold frequency
The minimum frequency of the electromagnetic radiation that will cause the emission of an electron from the surface of a particular metal.
Work function
The minimum energy needed to remove a single electron from the surface of a particular metal.
Photoelectrons
Electron emitted from the surface of a metal by the photoelectric effect
Wave particles duality
A theory that states that material has both particle and wave properties and electromagnetic radiation has both wave and photon nature.
