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All Physics Formula and Glossary

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Physical Quantity
Formula     
Remarks
Equations of motion at constant acceleration

Density 
 
Weight W = mg
W = weight, N
m = mass, kg
g = gravitational acceleration, m/s2 or N/kg
Force F = ma
F = force, N
m = mass, kg
a = acceleration, m/s2
Moment of a force about a point



Object in equilibrium with parallel forces acting on it
 
 
Work done
W = Fd


W = work done, J
F = force, N
d = displacement, m
Kinetic energy
K.E.= 1/2 mv2
K = kinetic energy, J
m = mass, kg
v = velocity, m/s
Potential energy
P.E. = mgh
Ep = potential energy, J
m = mass, kg
g = gravitational acceleration, N/kg or m/s2
h = gain/loss in height
Efficiency

 
Power 
P = power, W
W =  work done or energy transferred, J
t = time, s
E = energy transferred/used, J
Q = thermal energy transferred, J
Pressure 
 
Liquid pressure

Boyle's Law

Specific heat capacity



Specific latent heat of vaporization or fusion

Wave equation

Refractive index
n = refractive index
i = angle in air/vacuum
r = angle in medium
c = speed of light in vacuum, m/s
v = speed of light in medium, m/s
 Critical angle
 
Amount of charge
Q = It
Q = charge, C
t = time, s
Ohm's Law
 V = IR
V = potential difference, V
I = current, A
Potential difference
V = W/Q
V = potential difference, V
W = work done between two points, J
Q = charge, C
emf
 
 
Electrical power
P = IV = I2P = power, W
I = current, A
V = potential difference, V (voltage)
Electrical energy
E = VIT
E = electrical energy, J
Resistance
p = resistivity, ohm
l = length of wire, m
A = cross-sectional area of wire, m2
Transformer equations
 

   

Glossary

 Concept Definition
Acceleration
The rate of change of velocity. Value can be found from the gradient of a velocity-time graph.

unit = m/s2
Gravitational acceleration
The rate at which all objects fall towards earth if there were no air resistance, about 10m/s2 near earth's surface
Alternating current
An electric current that periodically reverses its direction in the circuit
Ampere (A)
The SI unit for electric current. A flow of 1 coulomb per second is 1 ampere
Amplitude
The maximum displacement of a point of a wave from rest position.
Height of a crest or depth of a trough measured from the undisturbed position.
For a sound wave, the greater the amplitude, the louder the sound.
Angle of incidence
The angle between an incident ray and the normal to a surface
Angle of reflection
The angle between a reflected ray and the normal to a surface
Angle of refraction
The angle between a refracted ray and the normal to a surface
Atmospheric pressure
The air pressure in the earth's atmosphere. Atmospheric pressure is about 105 Pa near sea level and decreases with height above ground.
Average speed
The total distance traveled divided by the total time taken.
Boiling
A process by which energy supplied changes a substance from liquid to gas without a change in its temperature.
Cathode ray oscilloscope
An instrument that enables a variety of electrical signals to be examined visually. It is used for measuring direct current and alternating current voltages, short time intervals and frequency and for displaying waveforms
Celsius scale
A temperature scale where the lower fixed point is the ice point and the upper fixed point is the steam point
Centre of gravity
 The point at which the entire weight of an object appears to act
Condensation
A process by which energy released changes a substance from gas to liquid.
Conduction
The process by which thermal energy is transmitted through a medium from one particle to another.
Convection
The process by which thermal energy is transmitted from one place to another by the movement of the heated particles of gas or liquid.
Converging lens
A lens that can bring a parallel beam of light passing through it focus to a point. It is thicker in the middle than at the edges.
Coulomb (C)
The SI unit of electric charge.
Crest
 The highest points on a wave
Critical angle
The angle of incidence in the optically denser medium for which the angle of refraction in the less dense medium is 90o
Total internal reflection occurs when the angle of incidence is greater than the critical angle.
Density
Mass per unit volume of a substance
Density = Mass / Volume
Diverging lens
A lens that causes parallel beams of light to diverge. It is thicker at the edges than at the centre.
Echo
Reflected sound heard after an interval of silence.
Electric current
The rate of flow of charge.
I = Q / t   [ I = current, Q = charge, t = time ]
Kelvin (K)
SI unit for temperature
K = oC + 273
Kinetic energy
The energy a body possess due to its motion.
Kinetic theory of matter
All matter is made up of large numbers of tiny atoms or molecules which are in continuous motion.
Latent heat of fusion
The energy needed to change a substance from solid to liquid without a change in temperature
Latent heat of vaporization
The energy needed to change a substance from liquid to gas without a change in temperature
(See image above)
Law of charges
 Like charges repel and unlike charges attract
Laws of refraction
1. The incident ray, refracted ray, and normal all lie in the same plane at the point of incidence.
2. The ration sini/sinr is constant 
[ i = angle of incidence, r = angle of refraction]
Law of reflection
1. The incident ray, reflected ray, and normal all lie in the same place at the point of incidence
2. The angle of incidence = angle of reflection
Lenz's law
States that the direction of the induced e.m.f. is in a direction that opposes the change producing it.
Liquid pressure
Pressure due to the weight of a column of liquid is given by pressure = hpg
[ h = height of column, p = density, g = gravitational field strength ]
Longitudinal waves
Waves which travel in a direction parallel to the direction of vibration eg sound wave
Magnetic materials
Materials that are attracted by a magnet.
Iron is easier to magnetise but loses its magnetism easily - soft magnetic material
Steel is harder to magnetise but does not lose its magnetism easily - hard magnetic material.
Hard magnetic materials are used to make permanent magnets.
Soft magnetic materials are used to make temporary magnets.
Manometer
 A U-tube containing liquid (mercury or water) used to measure gas pressure

Mass
A measure of the amount of substance in an object.
W = mg  [ W = weight, m = mass, g = gravitational acceleration ]
SI unit is kg
Melting
A process whereby energy supplied changes the state of a substance from solid to liquid without a change in temperature.
Moment of a force
The turning effect of a force.
Moment = Force x Perpendicular distance from the line of action of the force to the pivot
SI unit is Nm
Newton's Laws
1. An object at rest will remain at rest and an object in motion will continue in motion at a constant speed in a straight line if no resultant force acts on it.
2. The resultant force acting on a body is equal to the product of the mass and acceleration of the body; the direction of the force is the same as that of the object's acceleration.
3. For every action, there is an equal and opposite reaction.
Newton (N)
SI unit for force
Normal
A line that is perpendicular to a surface
Used in reflection and refraction
Ohm's law
States that current through a metal conductor is directly proportional to the potential difference across it provided that temperature and physical condition of the conductor remain unchanged.
R = V / I
Optical centre
The point midway between the lens' surfaces on its principal axis. Light rays passing through the optical centre are not deviated.
Parallelogram law of vector addition
If two vectors acting at a point are represented as the sides of a parallelogram drawn from that point, their resultant force is represented by the diagonal passing through that point of the parallelogram.
Parallel circuits
I = I1 + I2 + I3 + ...
V = V1 = V2 = V3
 PeriodHow much time it takes for one cycle (one complete wave) to pass and the units are always in terms of time. The faster a wave moves, its wave period becomes smaller. 
It is also the time taken for the crests, or any point on the wave, to move a distance of one wavelength.
 PascalSI unit for pressure. 1 pascal = 1 N/m2
 PitchThe pitch of a note depends on its frequency. Higher frequency --> higher pitch
 Potential difference
The difference between the electrical potential (voltage) between 2 points. The potential difference across a component in a circuit is defined as the work done to drive a unit charge through the component.
V = W/Q      [V = p.d., W = work done, Q = charge]
SI unit is volt (V)
 Potential divider/ potentiometer
A variable resistor used to vary voltage.
Potential energy
The energy stored in an object due to its position, state, or shape
Power
The rate of doing work
Power = work done/time taken OR energy change/time taken
SI unit is watt (W)
1 W =  1 Joule/s
Pressure
The force per unit area, measured in pascals or N/m2
P = F/A   [P = pressure, F = force, A = area]
Principal axis
A line joining the optical centre of a lens and perpendicular to the plane of the axis
Principal focus
The point on the principal axis whereby incident rays parallel to the principal axis onto a lens are converged to (or diverged from)
Principle of conservation of energy
States that energy cannot be created or destroyed but only changes from one form to another
Principle of moments
 When an object is not rotating or in equilibrium, the sum of anticlockwise moments about any point = sum of clockwise moments about the same point
RadiationThe transfer of energy by electromagnetic waves.
Factors affecting rate of energy transfer:
1. Surface temperature
2. Color
3. texture
4. Surface area

- higher at higher temperatures
- higher when black colour and rough surface
- lower when white colour and smooth surface
 Ray a narrow beam of light
 Real image
An image formed by a lens that can be captured on a screen
 RectifierAn arrangement consisting of one or more diodes for converting alternating current to direct current
 RefractionThe change in direction of a light wave or water wave as it crosses a boundary at an angle
Refraction occurs because the wave changes its speed in different media
 Refractive index
n = c/v
The ratio of the speed of light in vacuum to the speed of light in the medium
can be calculated using sini/sinr
The greater the value of the refractive index, the greater is the bending of light towards the normal as it passes from air into the medium
Resistance
The ratio of the potential difference across a conductor to the current flowing through it.
SI unit is ohm.
Factors affecting resistance:
1. length (directly proportional)
2. cross-sectional area (inversely proportional)
Resistors in series
Effective resistance = R1 + R2 + R3 +...
Resistors in parallel
Effective resistance =
Resultant force
When the forces acting on an object are unbalanced, a resultant force acts on the object and it accelerates or decelerates.
Right-hand grip rule
 
Scalar quantities
Physical quantities that have magnitude only
eg. mass, temperature, time, speed, distance
Specific heat capacity
The amount of thermal energy required to raise the temperature of a unit mass of a material by 1 K or 1oC
Specific latent heat of fusion
The amount of energy required to change a unit mass of a substance from solid to liquid without a change in temperature
Specific latent heat of vaporizationThe amount of energy required to change a unit mass of a substance from liquid to gas without a change in temperature
Steam point
The upper fixed point on the Celsius scale of temperature
Thermal energy
The total kinetic energy of the atoms or molecules in a body
Thermocouple
 A thermometer consisting of two wires of different metals joined together at the ends to form two junctions. If the two junctions are at different temperatures an e.m.f. is produced.
The bigger the temperature difference, the larger the e.m.f. produced.
Temperature
 A measure of the degree of hotness of a body
Transformer
A device used to change the voltage of an alternating current
Step-up transformer: has more turns in the secondary coil than in the primary coil --> this increases the voltage
step- down transformer: has fewer turns in the secondary coil than in the primary coil --> decreases the voltage.

For a transformer that is 100% efficient, output power = input power
Transducer
A device that transforms energy from one form to another. Input transducers transform other energy into electrical energy eg solar cells, microphones, thermistor, LDR.

Output transducers transform electrical energy to other forms of energy eg loudspeakers, LED and electrical meters
Transverse wave
Waves which travel in a direction perpendicular to the direction of the vibrations. eg rope waves, water waves

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