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CURRENT

Given an appropriate external force, the movement of electrons is from negatively charged atoms to positively charged atoms. This flow of electrons is called current (I). The symbol “I” is used to represent current. The amount of current is the sum of the charges of the moving electrons past a given point. An electron has …

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ATOMS

An atom is the smallest particle of an element that retains the characteristics of that element. Each of the known 110 elements has atoms that are different from the atoms of all other elements. This gives each element a unique atomic structure. According to the classic Bohr model, an atom is visualized as having a …

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MATTER, ELEMENTS AND COMPOUNDS

Matter is anything that occupies space and has weight. It may be found in any one of three states: solid, liquid, or gas. An element is the basic building block of nature. It is a substance that cannot be reduced to a simpler substance by chemical means. Examples of elements are gold, silver. The chemical …

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What is a Hydraulic Power Unit?

Hydraulic Power Units are the main driving components of hydraulic systems. Consisting mainly of a motor, a reservoir and a hydraulic pump, these units can generate a tremendous amount of power to drive most any kind of hydraulic ram. Hydraulic Power Units are based on Pascal’s law of physics, drawing their power from ratios of …

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Light units

Light is a physical phenomenon but is interpreted by psychological processes in our brain. It is, therefore, a bit more complex to measure than other physical processes. Some prerequisites have to be established in order to make objective measurements. One of these is the bandwidth of the light frequencies considered, and this is usually from …

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depth of field

When a lens is focused on an object, theoretically, the whole plane passing through the object and perpendicular to the optical axis should be in focus. Practically, objects slightly in front of and behind the object in focus will also appear sharp. This “extra” depth of sharpness is called depth of field. A wide depth …

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Refraction

When a light ray traveling through air or a vacuum enters a denser medium, it reduces its speed by index of refraction. Different media (which are transparent to light) have different indices of refraction. For example, the speed of light in air is 300,000 km/s and almost the same as in vacuum. If a light …

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contactless cards

The techniques used with contactless cards for transferring energy and data are not new. They have been common knowledge for many years in radio-frequency identification (RFID) systems, which have been used for a variety of applications, such as animal implants and transponders for electronic anti-start systems for vehicles. There are many techniques for identifying persons …

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