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ray diagrams
Shémas mpl des rayons

X-ray diagrams. These diagrams are drawn to allow the user to locate and describe the image of an object formed by a lens or mirror. In the system diagrams, three rays emanating from a point on the body are drawn, on a relative scale, on a relative scale. Where the three rays meet, or appear to meet, is the corresponding point on the image. The three rays are chosen according to the following, all of which have known behavior:
a) The ray entering a lens or mirror parallel to the axis then passes, or appears to pass, through the focal point.

b) The ray that passes, or appears to pass, through the point
The focal point leaves parallel to the axis.

c) The ray coming to the pole passes in a straight line (for a lens) or is reflected at the same angle on the other side of the axis (for a mirror).

d) The ray passing through the center of curvature of the mirror returns along the same line.

We describe the image by giving its location and size, and by saying whether it is upright like the body itself or not (upright or upside down) and whether it is real or imaginary.

Typical ray diagrams are provided in the lens, mirror, and microscope entries


rectifier
dresseur m

Rectifier. A device that allows current to flow only in one direction.
Most types of rectifiers are types of diodes, the symbol of which is shown below. See also valves.

The circuit shown in the drawing is a simple rectifier, of the type used in power trains - toys and microcomputers, for example. The input of the transformer is the main supply, which is an alternating current whose value is about 250 volts in Britain, while the output (A) is an alternating current that may be 12 volts. The two diodes form a full-wave rectifier with output (b). The single diode is a half-wave rectifier, and its output is as in (c).

(a) Potential difference across a resistance.
Alternating current input.
(b) Full wave DC.
(c) Half-wave DC.
(d) Normalized DC current.

A bridge rectifier circuit can be used instead of using the central branch of the transformer:

The output may not be stable enough for all uses, so the task of smooting capacitors is to make the signal as stable as required. This is shown in Figure (d).

Direct current supply is rarely used at high capacity, while alternating current supply is easier to transport. However, there are many uses of electricity that require constant current. Examples include: battery charging, electroplating, and almost all electronic systems. This is what makes the ingredients commonly used.


reed switch
Commutateur mà lames

Rishi interrupted. A coil of wire surrounds two “feathers,” or thin, easily magnetized nickel-iron strips sealed in a glass tube. A current passing through the coil magnetizes the two blades, causing them to attract and touch, completing the circuit. When an alternating current passes through the coil, the action of cutting and connecting the two blades can be at a frequency of 1000 Hz. This breaker can be used to produce pulsating current in telephone systems or as alarm bell breaker, etc.

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Two iron feathers
Glass capsule