| 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
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Alternating current
| An electric current that periodically reverses its direction in the circuit
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Ampere (A)
| The SI unit for electric current. A flow of 1 coulomb per second is 1 ampere
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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.
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Angle of incidence
| The angle between an incident ray and the normal to a surface
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Angle of reflection
| The angle between a reflected ray and the normal to a surface
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Angle of refraction
| The angle between a refracted ray and the normal to a surface
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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.
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Average speed
| The total distance traveled divided by the total time taken.
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Boiling
| A process by which energy supplied changes a substance from liquid to gas without a change in its temperature.
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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
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Celsius scale
| A temperature scale where the lower fixed point is the ice point and the upper fixed point is the steam point
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Centre of gravity
| The point at which the entire weight of an object appears to act
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Condensation
| A process by which energy released changes a substance from gas to liquid.
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Conduction
| The process by which thermal energy is transmitted through a medium from one particle to another.
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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.
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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.
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Coulomb (C)
| The SI unit of electric charge.
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Crest
| The highest points on a wave
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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.
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Density
| Mass per unit volume of a substance
Density = Mass / Volume
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Diverging lens
| A lens that causes parallel beams of light to diverge. It is thicker at the edges than at the centre.
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Echo
| Reflected sound heard after an interval of silence.
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Electric current
| The rate of flow of charge.
I = Q / t [ I = current, Q = charge, t = time ]
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Kelvin (K)
| SI unit for temperature
K = oC + 273
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Kinetic energy
| The energy a body possess due to its motion.
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Kinetic theory of matter
| All matter is made up of large numbers of tiny atoms or molecules which are in continuous motion.
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Latent heat of fusion
| The energy needed to change a substance from solid to liquid without a change in temperature
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Latent heat of vaporization
| The energy needed to change a substance from liquid to gas without a change in temperature
(See image above)
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Law of charges
| Like charges repel and unlike charges attract
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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]
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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
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Lenz's law
| States that the direction of the induced e.m.f. is in a direction that opposes the change producing it.
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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 ]
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Longitudinal waves
| Waves which travel in a direction parallel to the direction of vibration eg sound wave
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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.
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Manometer
| A U-tube containing liquid (mercury or water) used to measure gas pressure
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Mass
| A measure of the amount of substance in an object.
W = mg [ W = weight, m = mass, g = gravitational acceleration ]
SI unit is kg
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Melting
| A process whereby energy supplied changes the state of a substance from solid to liquid without a change in temperature.
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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
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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.
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Newton (N)
| SI unit for force
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Normal
| A line that is perpendicular to a surface
Used in reflection and refraction
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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
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Optical centre
| The point midway between the lens' surfaces on its principal axis. Light rays passing through the optical centre are not deviated.
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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.
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Parallel circuits
| I = I 1 + I 2 + I 3 + ...
 V = V 1 = V 2 = V 3
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| Period | How 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.
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| Pascal | SI unit for pressure. 1 pascal = 1 N/m2
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| Pitch | The pitch of a note depends on its frequency. Higher frequency --> higher pitch
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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)
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Potential divider/ potentiometer
| A variable resistor used to vary voltage.
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Potential energy
| The energy stored in an object due to its position, state, or shape
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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
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Pressure
| The force per unit area, measured in pascals or N/m2
P = F/A [P = pressure, F = force, A = area]
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Principal axis
| A line joining the optical centre of a lens and perpendicular to the plane of the axis
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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)
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Principle of conservation of energy
| States that energy cannot be created or destroyed but only changes from one form to another
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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
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| Radiation | The 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
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| Ray | a narrow beam of light
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Real image
| An image formed by a lens that can be captured on a screen
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| Rectifier | An arrangement consisting of one or more diodes for converting alternating current to direct current
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| Refraction | The 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
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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
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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)
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Resistors in series
| Effective resistance = R1 + R2 + R3 +...
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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.
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Right-hand grip rule
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Scalar quantities
| Physical quantities that have magnitude only
eg. mass, temperature, time, speed, distance
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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
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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
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| Specific latent heat of vaporization | The amount of energy required to change a unit mass of a substance from liquid to gas without a change in temperature
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Steam point
| The upper fixed point on the Celsius scale of temperature
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Thermal energy
| The total kinetic energy of the atoms or molecules in a body
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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.
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Temperature
| A measure of the degree of hotness of a body
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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
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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
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Transverse wave
| Waves which travel in a direction perpendicular to the direction of the vibrations. eg rope waves, water waves
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