Physics Unit 1 Definitions (As)

Front 1

Coulomb (C)

Back 1

Charge flow in one second when a current of 1 Amp flows

Front 2

Current

Back 2

Charge flowing per unit time

Front 3

Potential Difference

Back 3

Work done or energy transferred per unit charge

Front 4

Electromotive Force (Emf)

Back 4

The electrical energy produced per unit charge passing through the source

Front 5

Potential Difference across terminals

Back 5

Electrical energy delivered by the source per unit charge

Front 6

Resistance

Back 6

Potential difference across the current divided by the current through it.

Front 7

Ohm's Law

Back 7

The potential difference across a metallic conductor is proportional to the current through it, provided physical conditions do not change. Therefore resistance is constant

Front 8

Resistivity

Back 8

Resistance per unit length multiplied by cross sectional area.

Front 9

Superconductor

Back 9

A material that has zero electrical resistivity at and below a critical temperature. After the temperature is increases above the critical temperature resistance increases.

Front 10

Rate of energy transfer

Back 10

Energy per unit time which is also the definition of power

Front 11

Internal Resistance

Back 11

The loss of potential difference per unit current in the source when current passes through it.

Front 12

LDR

Back 12

Light dependent resistor. As light intensity increases, resistance decreases.

Front 13

Thermistor

Back 13

As heat increases, resistance decreases. This is because there are more semi-conductor free electrons as temperature increases.

Front 14

Frequency

Back 14

Number of complete cycles per second

Front 15

Time Period

Back 15

Time for one complete cycle

Front 16

DC

Back 16

Direct current - One value of current/voltage

Front 17

AC

Back 17

Alternating current - Which produces a current which creates a waveform

Front 18

Root Mean Square Value

Back 18

The root mean square value of an alternating current/voltage is the value of direct current that would give the same heating effect as the alternating current.

The root mean square value is 1/sqrt2 of the peak value.

Front 19

Y-gain or Y-sensitivity

Back 19

Potential difference/current per division

Front 20

Time base

Back 20

Time per division

Front 21

Positive temperature coefficient

Back 21

The resistance of a metal increases as temperature increases

Front 22

Negative temperature coefficient

Back 22

The resistance of a semiconductor decreases as temperature increases

Front 23

Alpha Paricles

Back 23

Particles that each consist of 2 protons and 2 neutrons emitted during alpha radiation

Front 24

Annihilation

Back 24

When a particle and an antiparticle meet, they destroy each other and become photons of equal energy

Front 25

Antibaryon

Back 25

A hadron consisting of 3 anti-quarks

Front 26

Antimatter/Antiparticles

Back 26

Antiparticles that each have the same rest mass and, if charged, have equal and opposite charge to the corresponding particle.

Front 27

Antiquark

Back 27

The antiparticle of a quark

Front 28

Atomic Number

Back 28

The number of protons in the nucleus of an atom

Front 29

Baryons

Back 29

A hadron consisting of 3 quarks

Front 30

Beta Minus Radiation

Back 30

Beta minus particles are fast moving electrons emitted by unstable neutron rich nuclei

Front 31

Beta Plus Radiation

Back 31

Beta plus particles are fast moving positrons emitted by a unstable proton rich nuclei

Front 32

De Broglie Hypothesis

Back 32

Matter particles have a wave like nature characterised by the de Broglie wavelength

Front 33

De Broglie wavelength

Back 33

The wavelength of a matter particle = h/p where h is planck's constant and p is the momentum of the particle

Front 34

De-excitation

Back 34

Process in which an atom loses energy by photon emission, as a result of an electron inside an atom moving from an outer shell to an inner shell

Front 35

Electron capture

Back 35

Process in which an inner shell electron of an atom is captured by the nucleus

Front 36

Electron volt

Back 36

Amount of energy equal to 1.6x10^-19J. It is defined as the work done when an electron is moved through a potential difference of 1V

Front 37

Energy levels

Back 37

The energy of an electron in an electron shell of an atom

Front 38

Excitation

Back 38

Process by which an atom absorbs energy without becoming ionised as a result of an electron inside an atom moving from an inner shell to an outer shell

Front 39

Feynmann Diagram

Back 39

Representations of the interaction between two particles or the decay of a particle

Front 40

Flourescence

Back 40

Glow of light from a substance exposed to ultraviolet radiation, causing the atoms to de-excite in stages and emit visible photons in the process

Front 41

Gamma Radiation

Back 41

High energy photons emitted by unstable nuclei

Front 42

Ground State

Back 42

Lowest energy state of an atom

Front 43

Hadron

Back 43

Particles and antiparticles that can interact via the strong interaction

Front 44

Isotope

Back 44

Atoms of an element with different number of neutrons and the same number of protons

Front 45

Ion

Back 45

A charged atom

Front 46

Ionisation

Back 46

Process of creating ions by exciting electrons in the ground state to remove an electron.

Front 47

Kaon

Back 47

A meson that consists of a strange quark/antiquark and another antiquark/quark

Front 48

Lepon

Back 48

Electrons, muons, neutrinos and their antiparticles are classified as leptons because they cannot interact through the strong interaction. They interact through the weak interaction and, in the case of electrons and positrons, through the electromagnetic interaction

Front 49

Lepton Number

Back 49

A lepton number is assigned to every lepton and anti-lepton, on the basis that lepton number is always conserved.

Front 50

Nucleon

Back 50

Proton or neutron

Front 51

Nucleon Number (Mass Number)

Back 51

Number of protons and neutrons in the nucleus of an atom

Front 52

Pair production

Back 52

When a gamma photon changes into a particle and an antiparticle, each with half the energy of the photon

Front 53

Quark Model

Back 53

A quark can join with an antiquark to form a meson, or with two other quarks to form a baryon

Front 54

Rest Energy

Back 54

Energy due to rest mass

Front 55

Specific Charge

Back 55

Charge/mass value of a charged particle

Front 56

Strangeness Number

Back 56

A strangeness number is assigned to every particle on the basis that strangeness is conserved in the strong interaction, but not in the weak interaction.

Front 57

Strong Interaction

Back 57

Interaction between 2 hadrons.

Front 58

Strong Nuclear Force

Back 58

Attractive force between nucleons that holds the nucleons in the nucleus

Front 59

Threshold Frequency

Back 59

Minimum frequency of light that can cause photoelectric emission

Front 60

Virtual Photon

Back 60

Exchange particle of the electromagnetic force; a photon exchanged between two charged particles so they can interact. The virtual photon has zero mass, charged, and infinite range

Front 61

W boson

Back 61

Exchange particle of the weak nuclear force; W bosons have a non-zero rest mass and can be charged.

Front 62

Wave Particle Duality

Back 62

Matter particles have a wave-like nature, as well as a particle-like nature.

Front 63

Weak Interaction

Back 63

Interaction between two leptons

Front 64

Weak Nuclear Force

Back 64

Force responsible for beta decau

Front 65

Work Function of a metal

Back 65

The minimum amount of energy needed by an electron to escape from a metal's surface.