Classified in Physics

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•Mass-energy equivalence

The physical principle that a Measured quantity of energy is equivalent to a measured quantity of mass. The equivalence Is expressed by Einstein's equation E = mc2, where E represents Energy, m the equivalent mass, and c the speed of light.

•Radioactivity -  refers to the particles which are emitted from Nuclei as a result of nuclear instability. Because the nucleus experiences the Intense conflict between the two strongest forces in nature, it should not be Surprising that there are many nuclear isotopes which are unstable and emit Some kind of radiation.

•Strong nuclear force – Acts Between all nucleons. Strongly attractive at a specific range of inter-particle Distance but repulsive at very short distances

•Nuclear binding energy – is The energy required to separate an atomic nucleus completely into its Constituent protons and neutrons, or, equivalently, the energy that would be Liberated by combining individual protons and neutrons into a single nucleus.

•Radioactive (nuclear)


Radioactive decay, also known As nuclear decay or radioactivity. The spontaneous breaking down of a nucleus Accompanied by the emission of radiation

•Nucleon – one of the particles That makes up the atomic nucleus. Each atomic nucleus consists of one or more Nucleons, and each atom in turn consists of a cluster of nucleons surrounded by One or more electrons.


An isotope is a specific Version of a nucleus in terms of number of protons and neutrons

•Radioisotope - A radioisotope Is an unstable type. Isotope which has an unstable nucleus that decays, Emitting alpha, beta, or gamma rays until stability is reached.

•Nuclide – also called nuclear Species, species of atom as characterized by the number of protons, the number Of neutrons, and the energy state of the nucleus.


A radionuclide (radioactive Nuclide, radioisotope or radioactive isotope) is an atom that has excess Nuclear energy, making it unstable. This excess energy can either create and Emit, from the nucleus, radiation etc.

•Alpha particle – Alpha Particle consists of 2 protons and 2 neutrons; Mass is 4 amu, Has the most Mass by far of the emissions; Always has kinetic energy when emitted.

•Beta particle – 2 forms of Beta particles exist

– ‘negatron’ (β-) is identical In charge and mass to an electron

– ‘positron’ (β+) has same Mass but opposite charge to an electron

Both types have very low mass (0 amu). Both have high kinetic energy when emitted.

•Gamma ray

Gamma is just EM energy – No Mass, no charge

Is normally emitted in Conjunction with particulate emission (usually shortly after)

Is due to change in binding Energies of nucleons

Gamma emission itself does not Alter number of protons or neutrons


Each specific nuclide has a Characteristic timing of decay. HALF LIFE is the time it takes for half of the Nuclei in a sample of a specific nuclide to decay.


‘Activity’ is the number of Decays per unit time occurring in a sample of radioactive material

-SI Unit is the Becquerel = 1 decay per second

•Transmutation - conversion of One chemical element into another

Decay often involves changing One particle type into another; Decay may also involve emission of both protons And neutrons. If any of those happen, the number of protons in the nucleus Changes, so not only does the nuclide change but the atom becomes a different Element!

– This is a ‘transmutation’


•Wavefront –Set of waves Travelling together, radiates out spherically from a point. Result is series of Parallel lines. All points on a wavefront can be considered a source of waves Of that same frequency and wavelength


a line can be drawn Perpendicular to the surface of the mirror. This line is known as a normal line

•Angle of incidence – The angle Between the incident ray and the normal

•Angle of reflection – The Angle between the reflected ray and the normal

•Specular reflection – Reflection Off of smooth surfaces such as mirrors or a calm body of water leads to a type Of reflection.

•Diffuse reflection – Reflection Off of rough surfaces such as clothing, paper, and the asphalt roadway leads to A type of reflection.

•Virtual image – are images That are formed in locations where light does not actually reach.

•Real image – are images formed On the same side of the mirror as the object and light passes through the Actual image location.

•Lens - is merely a carefully Ground or molded piece of transparent material that refracts light rays in such As way as to form an image.

•Convex – convex mirrors were Silvered on the outside of the sphere, minifies.

•Concave – Concave mirrors were Silvered on the inside of the sphere, magnifies.

•Convergent (converging) lens 

Designed to cause individual Rays or waves to come together to a point after leaving the lens.

•Divergent (diverging) lens 

Designed to cause individual Rays or waves to move farther apart after leaving the lens.

•Index of refraction (n) of a Material is the ratio of speed of light in a vacuum to speed of light in that Material

•Total internal reflection

is the reflection of the total Amount of incident light at the boundary between two media.

•Critical angle – 100% Reflection occurs (total internal reflection)

•Coherent light – Coherent wave Sources, such as lasers, produce light that is monochromatic. This means that Each wave has same frequency or wavelength. Each wave also has the same Amplitude, and they are in phase with one another.

•Laser – Light Amplified Stimulated Emission of Radiation


•Radiation – is the transport Of energy in the form of waves or particles through space or through a material Medium.

•Electromagnetic energy

- is the transport of energy through space as a Disturbance of electrical and magnetic waves


The vibrating electric and Magnetic fields regenerate each other to make up an EM.

•Spectrum –  is a complete range of variations of a Phenomenon.

•Electron binding force

•Electron binding energy

-is A measure of the energy required to free electrons from their atomic orbits.

-Binding Energy is measured in electronvolts (eV) since it is measuring energy required To move electron through a potential difference


quantity of energy required to Move 1 ELECTRON through a potential difference of one volt.


Occurs when an orbital electron Receives quantity of energy that equals energy for an allowable location change (ΔE). Excited electron will move to higher energy level.


Electrons don’t stay in Excited state, will ‘jump’ down to lower level very quickly.

Electron must give up ΔE in Order to return to original energy level and orbital level.

•Ionisation -  is the energy necessary to release an electron From the neutral atom.

Sufficient energy to ionise an Atom by collision with an orbital electron.

•Transparent - means NO energy Was removed from the wave during passage through matter.

-Wave Passes through without loss of intensity

•Opaque – means all energy is Absorbed by the matter.


Since quantity of energy Within a photon is specific, the photon may also be called a ‘quantum’

•Photon – A pulse of EM is a discrete Packet of energy called photon.



•Magnetic force

Attraction or repulsion that Arises between electrically charged particles because of their motion.

•Magnetic pole - are the points Of origin of magnetic forces

•Magnetic field - are zones Where magnetic lines of force are in effect

•Magnetism - produced by the Motion of charges, resulting in forces of attraction and repulsion.

•Magnetic field intensity – is A vector quantity whose magnitude is the strength of a magnetic field at a Point in the direction of the magnetic field at that point.

•Magnetic domain – The magnetic field of an individual iron atom is so strong that Interactions among adjacent atom cause large clusters of them to line up with One another. These clusters of aligned atoms are called magnetic domains.

•Ferromagnetism – is the Property of certain materials that enables them to form magnets and be Attracted to magnets.

•Retentivity (or remanance)

the ability of a substance to Retain or resist magnetization, frequently measured as the strength of the Magnetic field that remains in a sample after removal of an inducing field.

-"iron Is easily magnetized but has low retentivity"

•Permeability – is a measure of The amount of resistance encountered when forming a magnetic field in a Classical vacuum.

•Permanent magnet – are those That hold a net magnetic field on their own

– Must be ferromagnetic


a piece of metal that becomes Magnetic when an electric current is passed through or near it

•Solenoid - is a coil of wire Carrying a current

•Electric motor - involve Rotating coils of wire which are driven by the magnetic force exerted by a Magnetic field on an electric current. They transform electrical energy into Mechanical energy.

•Electromagnetic induction

-A Process of inducing voltage by change the magnetic field in loops of wire.

•Faraday’s Law – The EMF Induced in a circuit is proportional to the time rate of change of the magnetic Flux linking that circuit.

•Electromagnetism – a type of Physical interaction that occurs between electrically charged particles. The Electromagnetic force usually shows electromagnetic fields, such as electric Fields, magnetic fields, and light.

•Flux – Field lines through a Surface of magnetic field

•Flux linkage - Flux linkage Requires the relative motion to be non-parallel

Crossing the conductor with Field lines; Imagine the flux line cutting through the wire


-A Device which converts mechanical energy to electrical energy. Loop of wire is Placed within strong stationary magnetic field.

•Motor effect

-When Charge moves along the wire, there is perpendicular upward force on the charge. Since there is no conducting path upward, the force on the charge tugs the wire Upward.

•Generator effect

-When A wire with no initial current is moved downward, the charge in the wire Experiences a deflecting force perpendicular to its motion. There is a Conducting path in this direction, so the charge moves, constituting a current.


A device which converts AC from One voltage to another. A Transformer makes use of Faraday's law and the ferromagnetic properties of an Iron core to efficiently raise or lower AC voltages.

-two Coils of wire (primary and secondary) ; EMF source for primary coil


•Series circuit

Circuit that contains multiple Devices connected in series. (one after another)

•Parallel circuit

Circuit that contains multiple Devices connected in parallel. (on a different path)

•Switch –  is a device used for making and breaking Electric current through the circuit.

•Direct current - DC, the Flowing of charges in one direction.

•Alternating current - AC, the Flow of electric charge periodically reverses direction.

•Circuit rating

Current received by a electric Component or device operating under normal conditions.

•Circuit overload

If the current drawn by all The devices connected in a circuit is more than the maximum current rating for The given circuit, the condition is called overloading.


Circuit limiting devices (CLD) That opens circuit by destroying its conducting path, Device has conducting Path with low melting point.

•Circuit breaker

CLD that opens circuit by Moving two contacts apart when maximum allowable current level is exceeded. Separation of contacts opens the circuit loop, stopping flow of current.

•Class I device

Class 1 equipment relies for Its safety upon a satisfactory means of earthing from the equipment to the Circuit protective conductors of the fixed installation.

•Class II device

Class 2 equipment is also Commonly known as “double insulated”.  As There is no earth required for Class 2 equipment there is no reliance on the Earthing of the fixed installation for their safety.

•Leakage current

The current that flows through The protective ground conductor to ground.

•Short circuit

A short circuit is a very low Resistance conducting path to ground. This is normally due to a faulty Connection that is either bypassing the normal resistance path or creating a Parallel path to it.

•Residual current device (RCD)

A circuit-monitoring device. Operates On principle of normal circuit operation has equal current magnitude in active And neutral wires.

•Equipotential earthing

•Electric shock - The passing Of current through the body.


•Macroshock – Electric shock Due to current flow into body via skin is ‘macroshock’. Current flows through Large quantity of tissue so quantity of current to heart is only small portion Of what entered body (about 5%).

•Microshock is current Resulting from direct electrical connection to heart muscle.


·Net Charge

Unbalance of charge (different Number of electrons and protons, positive/negative net charge)

·Ion - A particle with a net charge is called an Ion.


The process of causing an atom Or molecule to have an imbalance od charge is called Ionization


Induction charging is a method Used to charge an object without actually touching the object to any other Charged object.

·Coulomb: SI unit of charge.


Conductors are materials that Permit electrons to flow freely from particle to particle.


are materials that impede the Free flow of electrons from atom to atom and molecule to molecule.


The ability to conduct Electricity.

·Grounding (earthing)

Connect an object to the Ground and discharge the object (remove the net charge)

·Charge Polarization

Polarization occurs when an Electric field distorts the negative cloud of electrons around positive atomic Nuclei in a direction opposite the field.

·Electric Dipole

An electric dipole is two Charged objects, with equal but opposite electric charges, that are separated By a distance.

·Electric Field

Zone which electric force is In effect.

·Electric Potential energy

the energy a charge has due to Its position relative to other charges.

·Electrical Potential

the amount of work needed to Move a unit charge from a reference point to a specific point against an Electric field.

·Volt – SI unit of electrical potential (Electrical potential = energy/charge)

·Potential Difference (voltage)

The difference in electrical Potentials between two locations. (Voltage drop)

·Electromotive Force (EMF)

Potential rise. An EMF source Provides the net fields to give electrons a flow direction and energy. Energy Is added to the charges as they move between locations.

·Battery -  is a device that converts chemical Energy to electrical energy

·Electric Current

Quantity of charge flowing Past a point in the conducting path per unit time. I = q/t

·Ampere: SI unit of electric current

·Conduction Electrons – An electron in the conduction band of a solid, where it is free to Move under the influence of an electric field.

·Ohmic Resistance – The category of opposition to the flow of current in a circuit that Results in heating of the conductor.

·Ohm: SI unit of Ohmic resistance.

·Electric Circuit – A circuit is a loop path for the movement of electrical energy from a Source to a user using the flow of charge.



Sound is a pressure Disturbance travelling through a medium, it Originates from the vibration of an object that disturbs the medium surrounding It.

•Reflection – Reflection of Sound is called an echo. The amount of reflection is dependent on the Dissimilarity of the two media.

•Refraction - A change in the Direction of wave as they pass from one medium to another.

•Energy wave transmission

Sound is a mechanical energy. When the particles are compressed or rarefacted, the energy is released as Kinetic and transferred to neighbouring particles by collisions.

•Energy wave absorption

Sound is pressure energy. Absorption is the transferring of wave energy to the medium through which it is Moving. The result is that there is less energy staying with the pressure wave.

The higher the absorption Percentage, the lower the percentage of wave energy is transmitted. 

•Natural frequency

Each object tends to vibrate At a specific frequency when a pulse of energy is added to it.

•Resonance – When the frequency Of incoming pulsed energy matches the natural frequency of an object, the Object’s amplitude of vibration increases greatly.

•Sound intensity

An objective measure of Quantity of sound. The quantity of energy per unit time passing through an Area. The greater the energy, the greater the displacement of the particles by The wave.

•Intensity level

Intensity=Power/area. Intensity level is the logarithmic measure of relative intensity (decibel).

•Decibel – 1 decibel = 0.1 bel; 10 dB= 1 bel

•Energy - Energy is the ability To do work. Energy = Power * time

•Power – Power is the quantity Of work done per unit time.

Power = Work / time; Power = Intensity * area


Magnitude of maximum Displacement from equilibrium. Crest/Trough to resting position.

•Doppler effect

Whenever there is relative Motion between the sender and receiver of sound, there is a frequency shift in The sound.

•Doppler shift - A change in Frequency due to the Doppler effect.


•Atmospheric pressure – The Earth’s atmosphere is the collection of the gas molecules that make up air. The air has weight And it presses against everything it touches. That pressure is called Atmospheric pressure, or air pressure.

•Temperature – We perceive the Effect of the kinetic energy of molecules as warmth. The relative measure of That warmth is temperature.

•Absolute zero –  is the lowest possible energy situation; no Translational kinetic energy is present

Absolute zero = 0° K = -273° C

•Heat – is the quantity of Energy being transferred from a warmer object (higher temperature) to a cooler Object (lower temperature). Heat is energy moving across a temperature gradient.

•Internal energy (thermal Energy)  - The sum of all of the forms of Kinetic energy plus potential energy within an object is its ‘internal energy’.

•Specific heat capacity

Specific heat capacity (c) is The quantity of heat (Q) required to change the temperature (T) of a unit mass (m) of a substance by 1 degree. ΔT = Q/(cm)

•Thermal expansion

is the relative quantity of Expansion of the object’s volume for a given rise in temperature.

•Heat conduction

Conduction involves direct Collisions between electrons of adjacent molecules;

The collision transfers the Energy from molecule to molecule;

Conduction requires close Proximity of molecules.


Convection involves movement Of molecules across a temperature gradient;

This requires mobile Molecules, so occurs in fluids only, not solids.


Radiant energy is energy Transported through space as waves;

Heat radiation is in the form Of electromagnetic (EM) energy waves.


Back and Forth motion occur about An equilibrium point.


a periodic displacement Relative to a baseline or equilibrium position that travels through space

•Periodic motion - motion Repeated in equal intervals of time.

•Period - is the time needed For one complete cycle of vibration to pass a given point, the time duration of One cycle.

•Frequency – Reciprocal of Period


Magnitude of maximum Displacement from equilibrium (Crest/trough to resting position)


•Wavelength - The wavelength is The distance from crest to crest (or from trough to trough)

•Phase – the position of the Wave at a point in time of its cycle

•Intensity – the average power Transfer over one period of the wave is used

•Wave propagation

the movement of waves, The Disturbance is ‘kept alive’ as it moves through space.

•Wave speed (velocity) – the Speed is the distance traveled by a given point on the wave (such as a crest) In a given interval of time.

•Transverse wave 

The direction of the Disturbance is perpendicular to the direction of propagation.

•Longitudinal wave 

The disturbance is along the same Plane as the direction of propagation

•Compression - Compression is Increased density of the medium

•Rarefaction – Rarefaction is Decreased density of the medium

•Constructive interference

The disturbances must be in The same direction (both crests or both troughs)

The result is increased Amplitude that is the sum of the two amplitudes

•Destructive interference 

The disturbances are in Opposite directions (one crest, one trough)

The result is decreased amplitude That is the sum of the two amplitudes


•Atom – An atom is the smallest particle into which an element can be divided without Losing its chemical identity. The atom is the smallest identifiable unit of an Element.

•Nucleus – The nucleus is the Small, dense region consisting of protons and neutrons at the center of an Atom.

•Proton – A proton is a Positively charge particle that resides within the atomic nucleus.

•Neutron – is a subatomic Particle contained in the atomic nucleus. It has no net electric charge

•Electron – a very small Particle of matter that has a negative charge of electricity and that travels Around the nucleus of an atom (travel in orbitals)

•Element – a material comprised Entirely of one type of atoms (all having the same number of protons); Can’t be Broken down into any simpler substance

•Atomic number – the sum of the Protons

•Atomic mass number - the total Number of neutrons and protons in the nucleus.

•Ion – An atom or a group of Atoms that has an electric charge.

•Isotope – Different atoms of a Chemical element in the periodic table all have the same number of protons, but May have a different number of neutrons in their nuclei. These different Versions of the same element are called isotopes.

•Compound – consist of atoms of Two or more different elements bound together; Compounds have chemical Properties that are different from each of their constituents; The only way to Break up a compound is to use chemical means

•Mixture – are combinations of Different elements but without the chemical bonding between the different Elements.


is a group of two or more Atoms bound together with shared electrons, and has no net charge.

•Volume – the measure of the 3D Space occupied by an object

•Density – the mass per unit Volume of a material

•Elasticity – is the relative Quantity of temporary change to an object’s shape that occurs in response to The application of a deforming force to it; When the force is removed, the Object’s shape would be restored.

•Tension – describes the Pulling force exerted by each end of a string, cable, chain.

•Compression – is the pushing Forces to different points on a material or structure.

•Solid – Maintains a fixed Volume and shape regardless of its container; Changes shape only when broken or Cut; Component particles are close together.

•Liquid – Is nearly incompressible; Maintains a relatively fixed volume regardless of pressure but has a variable Shape that adapts to its container; Component particles are close together and But move freely relative to one another

•Gas – Takes the volume and Shape of its container; Component particles are relatively far apart and move Freely relative to one another with virtually no inter-molecular interactions.

•Fluid – All fluids can flow And have indefinite shape; That would include both gases and liquids

•Pressure – P = F / A

is the ratio of quantity of Force exerted to the area over which it is distributed

•Volume flow rate – F = Av

is the quantity of fluid that Passes through a cross-sectional area of the path per unit time

•Laminar flow – is in regular Layers

Little energy is removed from The system due to minimal friction

•Turbulent flow – is chaotic Flow

Increased energy is removed From the system due to friction, generating heat; Turbulence causes reduced Flow rate relative to applied pressure


•Inertia –  refers to an object’s resistance to change in Its motion. Maintaining a ‘state of motion’ could include maintaining a steady Velocity, not just being stationary.

•Force – A force is an Influence that tends to change the state of motion of an object.

•Net force – The sum of all Individual applied forces

•Mechanical equilibrium - means The net force is zero

•Equilibrium rule

•Friction – an opposing or Resistive force to the applied force causing motion

•Mass – the quantity of matter In an object

•Weight – the force on an Object due to gravity

•Momentum – inertia of motion

•Impulse – the change in Momentum

•Work – W = Fd

Work (W) is the product of the Force (F) on an object and the distance (d) through which the object is moved By that force.

•Power – P = W / t – Power is The quantity of work done per unit time.

•Energy – Energy is the ability To do work. (Joules)

•Mechanical energy - is the Energy due to an object’s movement and relative position

•Potential energy – due to Relative position

When an object has work done On it to put it in a certain position relative to another location, the object Stores that energy as ‘potential energy’

•Kinetic energy – due to motion

Kinetic Energy is work that the Object can do while being brought to rest.

•Centre of mass – is the point Where all of the mass of the object is concentrated.

•Centre of gravity

a point from which the weight Of a body or system may be considered to act. In uniform gravity it is the same As the centre of mass.

•Stability – The position of The centre of gravity of an object affects its stability. The lower the centre Of gravity (G) is, the more stable the object.



the number of significant Figures quoted in a result should represent the accuracy of the result.


The smallest order of 10 used In the expression of the number indicates the precision. For level of Precision, look for the number of decimal places.

•Margin of error – is Understood to be one half of the size of the last significant place

•Significant digits – The Number of digits quoted in a measurement or result indicates how accurate the number Is.

•Scientific notation

An efficient and unambiguous Way to express the number of significant figures and the order of magnitude of A numerical result.

•Proportional relationship

When the causative variable’s Magnitude impacts the dependent variable’s magnitude in a predictable way, a Proportional relationship exists

•Dependent variable – The Affected variable is termed dependent

•Independent variable – The Causative variable is termed independent


the length between two locations Following the actual path used to connect those two locations


the length between two locations Measured along a straight line to connect those locations

•Speed – distance / time

•Velocity - is speed in a Specific direction

•Acceleration - is the time Rate of change in velocity

•Free fall

Any object that is being acted Upon only by the force of gravity is said to be in a state of free fall.

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