Definitions for EWP Flashcards
Absorption line spectrum
A dark line of a unique wavelength seen in a continuous spectrum
Ampere
The SI unit of electric current
Amplitude
The maximum displacement of a particle from its equilibrium position
Antinode
A point on a stationary wave with maximum amplitude
Charge carrier
Any charged particles such as electrons responsible for current
Coherent
To sources are coherent when they emit waves with a constant phase difference
Compression
A region in a sound wave where the air pressure is greater than its mean value
Constructive interference
When to waves reinforce to give increased amplitude
Coulomb
The SI unit of electrical charge. A charge of 1 C passes a point when a current of one amp flows for one second
Destructive interference
When to waves cancel to give reduced amplitude
Diffraction
The spreading of a wave when it passes through a gap or past the edge of an object
Dispersion
The splitting of light into its different wavelengths
Displacement
The distance moved by an object in a particular direction (measured from a fixed starting point)
Efficiency
The ratio of useful output energy to the total input energy for a device, expressed as a percentage
Efficiency = useful output energy/total input energy
Einstein relation
This refers to the equation for the energy of a photon
E = hf
E= hc/lambda
Electrical resistance
The ratio of potential difference to current. Unit is ohms
Electrolyte
An Electrically conducting solution. The conduction is due to positive and negative ions in the solution
Electromagnetic spectrum
The family of waves that travel through a vacuum at a speed of 3000 0000 0 m/s
Electro motive force
The energy gained per unit charge by charges passing for a supply. Unit J/C
Electron volt
The energy gained by an electron travelling through a potential difference of 1 V (1.6×10 to the -19)
Elementary charge
The smallest unit of charge that a particle or objects can have it has a magnitude of 1.6×10 to the -19 coulombs
Emission line spectrum
A sharp and bright line of a unique wavelength seen in a spectrum
Energy level
The quantised energy states of an electron in an atom
Frequency
The number of oscillations of a particle per unit time (HZ)
Fundamental frequency
The lowest frequency in a stationary wave for a particular system
Intensity
The power transmitted normally through a surface per-unit area
Intensity = power/cross sectional area
Interference
The formation of points of cancellation and reinforcement where to coherent waves pass through each other
Internal resistance
The resistance of an e.m.f. Source. The internal resistance of a battery is due to its chemicals
I V characteristic
Graph of current against voltage for particular component. You can identify the components from this Graph
Kilowatt hour
The energy transferred by a 1 kW device in a time of one hour
1 kWh = 3.6 MJ
Kinetic energy
The Energy of an object due to its motion
Kirchhoff’s first law
The sum of the currents entering any point in a circuit is equal to the sum of currents leaving same point. This law conveys the conservation of charge
Kirchhoff’s second law
That some of the e.m.fs round a look in a sec it is equal to the sum of the potential differences in that same loop
Light emitting diodes
A semiconductor component that emits light when it conducts
Longitudinals wave
A wave in which particles oscillate along the direction in which the wave travels
Lost volts
The difference between the e.m.fs and the terminal p.d. It is also equal to the voltage across the internal resistance
Magnetic field
A force field created by magnets and moving charges
Number density
The number of charged particles per unit volume
Ohms law
The current in a metallic conductor is directly proportional to the potential difference across its ends, provided its temperature remains constant
Path difference
The difference in the distances travelled by two ways from coherent sources at a Particular point
Node
A point on a stationary wave with zero amplitude
Path difference
The difference in the distances travelled by two ways from coherent sources at a particular point
Period
The time taken for one complete oscillation of a particle
Photon
A quantum packet of electromagnetic energy
Plane polarised
Describes transverse waves that oscillate in only one plane
Potential difference
The energy lost per unit charge by charges passing through a component
Potential divider
The circuit in which two or more components are connected in series to supply. The output voltage from the circuit is taken across one of the components
Power
The rate at which energy is transferred or the rate at which work is done
Principle of superposition
When two or more waves meet at a point, The resultant displacement is the sum of the displacements of the individual waves
Progressive wave
A wave that carries energy from one place to another
Rarefraction
A region in a soundwave where air pressure is less then its mean value
Reflection
The bouncing back of a wave from a surface
Refraction
The change in direction of a wave as it crosses an interference between two materials where its speed changes
Resistivity
The property of a material defined by:
Resistivity = resistance X cross-sectional area/length
Resistor
And electrical component whose resistance in a circuit remains constant. Its resistance is independent of current or potential difference
Semiconductor diode
And electrical component made from a semiconductor material that only conduct in one direction. A diode in ‘reverse bias’ has infinite resistance
Stationary wave
A wave pattern produced when two progressive waves of the same frequency travelling in opposite directions combine. It is characterised by nodes and antinodes. Also known as a standing wave
Terminal potential difference
The potential difference across the external resistor connected to an EMF source
Threshold frequency
The minimum frequency of the electromagnetic radiation that will eject electrons from the surface of the metal
Threshold voltage
The minimum forward bias voltage across a LED when it starts to conduct and emit light
Transition
When an electron makes a jump between two energy levels
Transverse wave
A wave in which the oscillation is at right angles to the direction in which the wave travels
Wave
Periodic disturbance travelling through space, characterised by vibrating particles
Wavelength
The rate of change of the displacement of an object
Velocity = change in displacement/time
Work function
The minimum energy required by a single electron to escape a metal surface
