applied science and maths Flashcards
(16 cards)
what is luminous intensity measured in?
candela
what is candela used for?
Candela is useful in calibrating artificial light sources such as light bulbs or LEDs.
Candela can be measured using a digital photometer.
Calculating illumination can be useful when designing building interiors, rooms or public open spaces. It is also useful when designing the lighting for a photo shoot or a movie set.
what is candela ?
The candela is the unit of measurement for the amount of light (also known as luminous intensity) recognised by the human eye.
what is current and what is it measured in?
The ampere, symbol A, is the SI unit of electric current. Current is a count of the number of electrons flowing through a circuit.
An ampere is defined by a fixed value of the elementary change e (change of a proton or electron). This cumulates in an ampere being 6.241509074 × 1018 electrons’ worth of charge, moving past a point in a second. One amp is also the amount of current produced by a force of one volt acting through the resistance of one ohm.
what is temperature and how does it differ with heat
Temperature is a measure of the average kinetic energy of the particles making up the substance being examined.
Temperature must not be confused with heat. Heat is the amount of vibrational energy contained in a particular mass.
For any temperature scale, it is necessary to have two fixed points. These are temperatures at which physical properties manifest themselves, for example melting or boiling.
how is temperature measured?
The kelvin, symbol K, is the primary unit of temperature in the International System of Units (SI), used alongside its prefixed forms and the degree Celsius. The kelvin is the primary unit of temperature for engineering and the physical sciences, while Celsius is the dominant scale outside of these fields.
The Celsius scale (°C) of temperature is a scale of temperature.
It is based upon two “fixed” points:
The melting point of pure ice (0°C).
The boiling point of pure water (100°C).
how would you convert from degrees to kelvin?
0 degrees Celsius is equal to 273.15 degrees kelvin: 0°C = 273.15 K
The temperature T in kelvin is equal to the temperature T in degrees Celsius (°C) plus 273.15: T(K) = T(°C) + 273.15
what is mass?
Mass is a measure of the amount of or matter material in an object and is measured in kilograms.
Other units that are accepted as the units of mass are gram (g) and its multiples and submultiples, a tonne (t), electronvolt (eV), the atomic mass unit (u) which is most convenient for expressing the masses of atoms and molecules.
how do mass and weight differ?
The difference between mass and weight is that mass is the quantity of matter that is contained in an object. It is a constant quantity measured in kilograms and is a scalar quantity.
Whereas weight is the force with which an object gets pulled towards the Earth. It is not a constant quantity, measured in Newton and is a vector quantity.
what is the si unit for length?
Metre is the SI unit of length and is defined by how far light travels in a vacuum during a time interval of 1/(2.99 792 458 × 108) second.
Length also has its multiples and submultiples. The multiples are for expressing units larger than the metre and the submultiples are for expressing smaller measures. Some examples of these are:
Micrometre (μm) = 10−6 m
Millimetre (mm) = 10-3 m
Centimetre (cm) = 10-2 m
Kilometre (km) = 103 m
give some examples of where derived units may be used in the engineering world
Power
watt
W
Used with electrical appliances, cars, trucks, motorcycles or trains.
Pressure
pascal
Pa
Aircrafts design, submarine design or diving equipment design.
Electric charge
coulomb
C
Printers and photocopiers where static electric charges attract the ink, or toner, to the paper, air filters, and dust removal.
Name
Unit
Abbreviation
Applications
Power
watt
W
Used with electrical appliances, cars, trucks, motorcycles or trains.
Pressure
pascal
Pa
Aircrafts design, submarine design or diving equipment design.
Electric charge
coulomb
C
Printers and photocopiers where static electric charges attract the ink, or toner, to the paper, air filters, and dust removal.
Electric potential difference
volt
V
Power stations, household appliances and integrated circuits.
Electric resistance
ohm
Ω
Power stations, household appliances and integrated circuits.
what is efficiency
Efficiency is the ratio of the useful power output from a system to its total power input.
If a system has high efficiency, this means most of the energy transferred is useful. If a system has low efficiency, this means most of the energy transferred is wasted.
what is power?
Power is the rate of work done or energy converted with respect to time. It is measured in watts.
power = energy ÷ time P = E ÷ t
what is workdone?
Work done is the force needed to move an object multiplied by the distance moved in the direction of the force. It is measured in joules.
what is density?
Density is the amount of mass per unit volume of an object. Density is a measure of how tightly the mass of an object is packed into the space it takes up.
what is area?
An area is an amount of surface a two-dimensional shape can cover and is measured in square units.
