Electricity

The candela; (cd) is the unit of luminous intensity in the International System of Units (SI), that is luminous power per unit solid angle emitted by a point light source in a particular direction. Luminous intensity is analogous to radiant intensity, but instead of simply adding up the contributions of every wavelength of light in the source's spectrum, the contribution of each wavelength is weighted by the standard luminosity function (a model of the sensitivity of the human eye to different wavelengths). A common wax candle emits light with a luminous intensity of roughly one candela. If emission in some directions is blocked by an opaque barrier, the emission would still be approximately one candela in the directions that are not obscured. The word candela is Latin and Italian for candle.

The SI base units are the standard units of measurement defined by the International System of Units (SI) for the seven base quantities of what is now known as the International System of Quantities: they are notably a basic set from which all other SI units can be derived. The lighting related units and their physical quantities are the ampere for electric current, the kelvin for thermodynamic temperature, and the candela for luminous intensity. The SI base units are a fundamental part of modern metrology, and thus part of the foundation of modern science and technology. The names and symbols of SI base units are written in lowercase, except the symbols of those named after a person, which are written with an initial capital letter. For example, the metre has the symbol m, but the kelvin has symbol K, because it is named after Lord Kelvin and the ampere with symbol A is named after André-Marie Ampère. [Read more...]

The Volt (symbol: V) is the unit of electric potential, electric potential difference (voltage), and electromotive force in the International System of Units (SI). It is named after the Italian physicist Alessandro Volta (1745–1827). One volt is defined as the electric potential between two points of a conducting wire when an electric current of one ampere dissipates one watt of power between those points. Equivalently, it is the potential difference between two points that will impart one joule of energy per coulomb of charge that passes through it.

The Watt (W) is a unit of power. It is defined by the internal system of units as a unit derived from 1 kg⋅m2⋅s−3 (1 joule per second). To describe watts in different multiples, the words below are used. Microwatt - (µW) - 1 millionth of a W (10-6 W) Milliwatt (mW) - 0.001W Centiwatt (cW) - 0.01W Deciwatt (dW) - 0.1W Watt - (W) - 1W Decawatt (daW) - 10W Hectowatt (hW) - 100W Kilowatt (kW) - 1000W Megawatt (MW) - 1 million W (106 W) To see more Watt multiples, view Orders of magnitude (power) (Wikipedia).

The ampere (amp/A) is the SI base unit for electronic current and is equal to one coulomb per second (C/s). In other words, it is equal to 6.241509074×10¹⁸ electrons worth of charge moving past a point in a second. It is named after French mathematician and physicist André-Marie Ampère.

Leading and Trailing edge are types of dimmers. Leading edge dimmers were originally used for dimming incandescent and halogen lamps. Because of this, they have a high minimum load which makes them less useful for low energy lighting such as LEDs. Trailing edge dimmers have many more benefits, including reduced buzzing and smoother dimming, They also have a lower minimum load, making them more suitable for lower energy lighting including LEDs.

The Kelvin (K) is the SI base unit of temperature, named after the Belfast-born engineer and physicist William Thomson, 1st Baron Kelvin (1824–1907). Kelvin uses absolute zero as the null point (0°K) which is equivalent to -273°C (Celsius) or -459.67°F (Fahrenheit).

One Kilowatt hour (kWh) is equal to one thousand Watts sustained for an hour. Its SI base unit symbol is kWh. In terms of human power, a healthy adult male manual labourer performs work equal to about half a kilowatt-hour over an eight-hour day.

An LED driver is a self contained power supply which regulates the power applied to an LED or set of LEDs. The temperature of an LED light fluctuates, which is why the LED driver is important. Without one, the LEDs would become too hot and may fail or become damaged.

The lumen (L) is the the unit for luminous flux, which is a measurement of how much visible light is emitted over time. "If a light source emits one candela of luminous intensity uniformly across a solid angle of one steradian, the total luminous flux emitted into that angle is one lumen (1 cd·1 sr = 1 lm). Alternatively, an isotropic one-candela light-source emits a total luminous flux of exactly 4π lumens. If the source were partly covered by an ideal absorbing hemisphere, that system would radiate half as much luminous flux—only 2π lumens. The luminous intensity would still be one candela in those directions that are not obscured." - Wikipedia

A heat sink is a heat exchanger which passively transfers the heat generated by a device away from itself by using an air or a liquid coolant, thereby allowing regulation of the temperature of the device. Heat sinks are important for LEDs as the thermal energy must be dissipated into the surroundings in order for the light to function properly. The heat sink is the last component in the thermal path of an LED luminaire and is also the most important. Heat sinks are manufactured using a variety of metal forming approaches, the most commonly used methods being casting, cold forging, extrusion and stamping. Other methods are also used such as bonding, forging, die cast, extrusion, stamping, machining, and stripping.

The difference between a DP (Double Pole) and SP (Single Pole) switches is that a SP switch breaks the live, and in a DP the Live and Neutral. A single pole switch has one input and output, and has two states; “on” or “off”. They can be wired normally open or normally closed, and can also either be latching or momentary. A double pole switch has two connections to 2 separate circuits, making them essentially 2 switches in one. The connections can either be staggered or connect simultaneously.

A dichroic reflector is used for display lighting and allows heat to pass through while reflecting the light in a cool beam that does not heat the display. You can tell dichroics apart from a ordinary lamp by shining a light at the back of it, if it's dichroic it will pass through and show a pink hue.

The IP (Ingress Protection) rating presents the level of protection a light fixture has against dirt and water. Any fixture that is used in a bathroom, wet environment or outdoors should have an IP rating that is high enough to stop dirt or water entering the fixture, as to protect it from being damaged. An IP rating consists of two digits. The first digit represents protection against the ingress of solid objects, and the second digit represents protection against the ingress of liquids. The higher the value of either digit, the greater the protection. Please see this Blog for more details about IP in Bathrooms.