Module 4 definitions

Question 1

Conductors

Answer 1

A material that allows the flow of electrical charge. Good conductors have a larger amount of free charge carriers to carry a current

Question 2

Conservation of charge

Answer 2

the total charge in a system cannot change

Question 3

Conventional current

Answer 3

The flor from positive to negative, used to describe the direction of current in a circuit

Question 4

coulomb

Answer 4

the unit of charge

Question 5

electric current

Answer 5

the rate of flow of charge in a circuit

Question 6

electrolytes

Answer 6

substances that contain ions that when dissolved in a solution, act as charge carriers and allow current to flow

Question 7

electron flow

Answer 7

the opposite direction to conventional current flow. Electrons flow from negative to positive

Question 8

elementary charge

Answer 8

the smallest possible charge, equal to the charge of an electron

Question 9

insulators

Answer 9

a material that has no free charge carriers and so doesn’t allow the flow of electrical charge

Question 10

kirchhoff’s first law

Answer 10

a consequence of the conservation of charge. The total current entering a junction must equal the total current leaving it

Question 11

mean drift velocity

Answer 11

The average velocity of an electron passing through an object. It is proportional to the current, and inversely proportional to the number of charge carriers and the cross-sectional area of the object

Question 12

quantisation of charge

Answer 12

the idea that charge can only exist in discrete packets of multiples of the elementary charge

Question 13

semiconductors

Answer 13

a material that has the ability to change its number of charge carriers, and so its ability to conduct electricity. Light dependent resistors and thermistors are both examples

Question 14

diode

Answer 14

a component that allows current through in one direction only. In the correct direction, diodes have a threshold voltage (typically 0.6 V) above which current can flow

Question 15

electromotive force

Answer 15

the energy supplied by a source per unit charge passing through the source, measured in volts

Question 16

filament lamp

Answer 16

a bulb consisting of a metal filament, that heats up and glows to produce light. As the filament increases in temperature, its resistnace increases since the metal ions vibrate more and make it harder fore the charge carriers to pass through

Question 17

I-V characteristics

Answer 17

plots of current against voltage, that show how different components behave

Question 18

kilowatt-hour

Answer 18

a unit of electrical energy. It is usually used to measure domestic power consumption.

Question 19

light-dependant resistor

Answer 19

a light sensitive semiconductor whose resistance increases when light intensity decreases

Question 20

ohm

Answer 20

the unit of resistance

Question 21

ohmic conductor

Answer 21

a conductor for which the current flow is directly proportional to the potential difference across it, when under constant physical conditions

Question 22

ohm’s law

Answer 22

the current and potential difference through an ohmic conductor held under constant physical conditions are directly proportioinal, with the constant of proportionality being resistance

Question 23

potential difference

Answer 23

the difference in electrical potential between two points in a circuit. It is also the work done per coulomb to move a charge from the lower potential point to the higher potential point. It is measured in volts

Question 24

power

Answer 24

the rate of energy transfer in a circuit. It can be calculated as the product of the current and the potential difference between two points. It is measured in Watts.

Question 25

resistance

Answer 25

a measure of how difficult it is for current to flow through a material

Question 26

resistivity

Answer 26

a measure of how difficult it is for charge to travel through a material. It is proportional to the object's resistance and corss-sectional area, and inversely proportional to the object's length. It is measured in Ohm metres

Question 27

resistor

Answer 27

a device that has a fixed resistance and follows ohm;s law

Question 28

volt

Answer 28

the unit of potential difference

Question 29

conservation of energy

Answer 29

energy cannot be created or destroyed - it can only be transferred into different forms

Question 30

internal resistance

Answer 30

the resistance to the flow of charge withing a source. Internal resistance results in energy being dissipated within the source

Question 31

kirchhoff's second law

Answer 31

a consequence of the conservation of energy. The sum of the voltages in any closed loop must equal zero

Question 32

lost volts

Answer 32

the difference between a source's emf and the terminal voltage. It is equal to the potential difference across the source's internal resistance

Question 33

parallel circuit

Answer 33

components are said to be connected in parallel when they are connected across each other {seperate loops)

Question 34

potential divider

Answer 34

a method of splitting a potential difference, by connecting two resistors in series. The total potential difference is split in the ratio of their resistances

Question 35

resistors in parallel

Answer 35

the potential difference across resistors connected in parallel is identical for each resistor. The current is split between the resistors. The total resistance is equal to the inverse of the sum of the inverses of the resistances of the resistors

Question 36

resistors in series

Answer 36

the current through resistors connected in series is identical for reach resistor. The potential difference is split in the ratio of their resistances. The total resistance is equal to the sum of the resistances of the resistors

Question 37

sensor circuits

Answer 37

a circuit that reacts to external conditions. They commonly involve a semiconductor connected in a potential divider arrangement

Question 38

series circuit

Answer 38

components are said to be connected in series when they are connected end to end (in one loop)

Question 39

terminal PD

Answer 39

the potential difference across the terminal of a power source. it is equal to the source's emf minus any voltage drop over the source's internal resistance

Question 40

amplitude

Answer 40

A wave’s maximum displacement from its equilibrium position.

Question 41

antinodes

Answer 41

a position of maximum displacement in a stationary wave

Question 42

coherence

Answer 42

waves with the same frequency and constant phase difference

Question 43

citical angle

Answer 43

the angle of incidence that results in an angle of refraction of exactly 90. It is when the refracted ray travels along the boundary line

Question 44

destructive interference

Answer 44

the type of interference that occurs when the two waves are in antiphase. When one wave is at a peak and one is at a trought their addition results in a minimum point

Question 45

diffraction

Answer 45

the spreading of waves as they pass through a gap of a similar magnitude to their wavelength

Question 46

displacement

Answer 46

the distance that a point on a wave is from its equilibrium position

Question 47

electromagnetic spectrum

Answer 47

the spectrum of electromagnetic waves, consisting of gamma rays, x rays, ultraviolet, visible light, infrared, microwaves, and radiowaves

Question 48

electromagnetic waves

Answer 48

waves that consist of perpendicular electric and magnetic oscillations. All electromagnetic waves travel at the speed of light in a vacuum

Question 49

frequency

Answer 49

the number of waves that pass a point in a unit time period. It is the inverse of the time period

Question 50

fundamental mode of vibration

Answer 50

the oscillation of a wave at its natural frequency

Question 51

intensity

Answer 51

the power transferred per unit area. It is proportional to the square of a wave's amplitude

Question 52

interference

Answer 52

the superposition of the amplitudes of waves when they meet

Question 53

longitudinal waves

Answer 53

a wave with oscillations that are parallel to the direction of energy propoagation. Sound waves are an example of a longitudinal wave. They cannot travel through a vacuum

Question 54

nodes

Answer 54

a position of minimum displacement in a stationary wave

Question 55

oscilloscope

Answer 55

a device used to display and analyse waveforms

Question 56

path difference

Answer 56

a measure of how far ahead a wave is compared to another wave, usually expressed in terms of the wavelength

Question 57

period

Answer 57

the time taken for a wave to complete one full cycle

Question 58

phase difference

Answer 58

the difference in phase between two points on a wave. It is usually expressed in radians

Question 59

polarisation

Answer 59

the restriction of a wave so that it can only oscillate in a single plane. This can only occur for transverse waves

Question 60

progressive waves

Answer 60

waves that transfer energy from one point to another without a transfer of matter

Question 61

reflection

Answer 61

the bouncing of a wave at a boundary. The angle of incidence will equal to the angle of reflection

Question 62

refraction

Answer 62

the changing of speed of a wave as it passes into a new medium. If it passes into an optically denser medium, it will slow down

Question 63

refractive index

Answer 63

a material property that is equal to the ratio between the speed of light in a vacuum, and the speed of light in a given material

Question 64

stationary wave

Answer 64

a wave that stores, but does not transfer energy

Question 65

superposition

Answer 65

when two waves meet at the same point in space their displacements combine and the total displacement at that point becomes the sum of the individual displacements at that point

Question 66

total internal reflection

Answer 66

an effect that occurs in optical fibres, where full reflection occurs at the inside boundary of the fibre, meaning no radiation passes out. The angle of incidence must be greater than the critical angle for this to occur

Question 67

transverse waves

Answer 67

a wave with oscillations that are perpendicular to the direction of energy propagation. Electromagnetic waves are examples of transverse waves

Question 68

wave speed

Answer 68

the produce of wave's frequency and wavelength

Question 69

wavelength

Answer 69

the distance between two identical positions on two adjacent waves. It is commonly measured from peak to peak or trough to trough

Question 70

young double-slit experiment

Answer 70

an experiment that demonstrates the diffraction of light passing monochromatic light across two narrow slits and observing the resulting pattern of bright and dark fringes

Question 71

atom spacing

Answer 71

the distance between adjacent atoms in a crystal lattice, significant in electron diffraction experiments

Question 72

de broglie equation

Answer 72

an equation that relates the wavelength of a particle to its momentum: lamda = h/p where lamda is wavelength, h is plancks constant and p is the momentum of the particle

Question 73

diffraction (electron diffraction)

Answer 73

the bending and spreading of electrons when they pass through a narrow slit or around an obstacle, providing evidence of their wave-like properties

Question 74

electron diffraction

Answer 74

an experimental observation of electrons displaying wave-like behavior when passing through thin materials like polycrystalline graphite

Question 75

electronvolt (eV)

Answer 75

a unit of energy equal to the amount of kinetic energy gained by an electron when accelerated through a potential difference of 1 volt: 1eV = 1.6 x 10^(-19) J

Question 76

photon

Answer 76

a quantum (or packet) of electromagnetic energy. Photons exhibit both particle-like and wave-like properties

Question 77

photon model

Answer 77

a model of electromagnetic radiation that treats light as being made up of photons, explaining phenomena like the photoelectric effect that the wave model cannot

Question 78

photon energy

Answer 78

the quantised energy carried by a photon, given by the equation E = hf, where E is energy, h is Planck's constant, and f is the frequency of the radiation

Question 79

photoelectric effect

Answer 79

the emission of electrons from a metal surface when exposed to electromagnetic radiationi of sufficient frequency. This effect provides evidence for the particle nature of light

Question 80

photoelectric equation

Answer 80

an equation describing the photoelectric effect: hf = phi + KEmax, where hf is the energy of the incident photon, phi is the work function of the material, and KEmax is the max KE of the emitted photoelectrons

Question 81

planck constant (h)

Answer 81

a fundamental constant in quantum physics that relates the energy of a photon to its frequency: h = 6.63 x 10^(-34) J

Question 82

threshold frequency

Answer 82

the minimum frequency of incident radiation required to eject electrons from the surface of a material in the photoelectric effect

Question 83

wave-particle duality

Answer 83

the concept that all particles exhibit both wave-like and particle-like properties. This is evidenced by phenomena like the photoelectric effect (particle nature) and electron diffraction (wave nature)

Question 84

work function (phi)

Answer 84

the minimum energy required to remove an electron from the surface of a metal. It is a material-specific constant (although in later study is dependant on the contamination and roughness of the surface of the material as well)