The lumen (symbol: lm) is the unit of the International System of Units to measure the luminous flux, a measure of the light power emitted by the source. The luminous flux of radiant flux difference that the former provides the variable sensitivity of the eye to different wavelengths of light and the latter involves all electromagnetic radiation emitted by the source according Wien law and Stefan-Boltzmann regardless of whether such radiation is visible or not. 1 lm = 1 cd. sr = 1 lx. m2

VDC would be the abbreviation for Volt Direct Current which translated would volts direct current. The idea of ??this type is unidirectional current to the load. Direct current is normally produced by batteries, thermocouples, solar cells and a dynamo electric machine type. The direct current can flow in conductors such as wires, but may also flow through semiconductors, insulators ... In the image: 1 - current per pulse 2 - Direct Current (DC) 3 - Alternating Current (AC) 4 - Variable Current

VAC would be the abbreviation of Volt Altern Current which would be translated Volts of alternating current. The difference between VDC is that its sinusoidal oscillation achieving a more efficient energy transmission.

The alternating current is the energy that we receive in our homes, it is generated in the power plants by means of alternators.

The intensity of this type of current varies with time, and changes direction 50 times throughsecond (50hz). The generated voltage changes in the form of sine wave so it is not constant.

In the image:

1. Current by pulsations.
2. Direct current (DC).
3. Alternating current (AC).
4. Variable current.

Li-Ion or Lithium batteries are one of the most common batteries used today.
We can find this type of batteries in mobile phones, wireless headphones, SAIS, smart watches, cars etc.

Lithium is a very light metal capable of generating ions easily so it is ideal for the manufacture of batteries.

Unlike other types of batteries are a bit more expensive, but acThey are much smaller and lighter, capable of doubling the duration of a Ni-Cd.

Thanks to their composition can be manufactured in different ways, adapting to the device where they should be located, as well as its low memory effect makes them ideal for any type of device.

Summing up their positive points:

• Easy to find
• Many different sizes and shapes
• Small size