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Glossary T

Terminal Velocity
When an object which is falling or acted
on by a constant driving force it is subjected to a resistance
or drag force which increases with velocity, at some point it
will reach a maximum velocity where the drag force equals the
driving force or weight in the case of falling. After the object
has reached this velocity it will fall at that velocity, this
is called the terminal velocity. [NASA]
Thermistor
Is a semiconducting material used to
measure temperature changes, relying on the principle that the
resistance of a semiconductor decreases as the temperature increases.
Thermistors are usually a thin coil of a semiconducting material.
They work because raising the temperature of a semiconductor increases
the number of electrons able to move about and carry charge –
it promotes them into the conducting band. The more charge carriers
available, the more current a material can carry. [more]
Thermocouple
Is a temperature measurement device that
works by measuring the voltage produced between conductors placed
in hot and cold bodies. Thermocouples rely on the thermoelectric
effect. [more]
Thermoelectric effect
A an electromotive force (EMF) is produced
between conductors placed in the two bodies. By measuring the
voltage between them, the change in temperature between the bodies
can be found. Then if the absolute temperature of one is known
the other can be worked out.
Thermopile
A device for measuring the heat radiation. It is made
from rods of antimony and bismuth, connected in series.
When the device is placed near a hot object, thermoelectric
currents flow due to the thermoelectric effect, this current
is then measured.
Transistor
The transistor is an amplifying or switching
semiconductor device. The transistor is the key component in all
modern electronics. In digital circuits, transistors are used
as electrical switches, and arrangements of transistors can function
as logic gates, RAM-type memory and other devices. In analog circuits,
transistors are essentially used as amplifiers. [more]
Transverse wave
Means the electric and magnetic field
vectors are perpendicular to the direction that the wave travels
Tyndall effect
If a beam of converging rays, say, from a projection lantern,
is passed through a liquid containing minute particles in suspension,
each of these particles scatters the light rays that fall on it,
becoming, in a sense, a luminous point. Thus, the entire path
of the rays through the liquid becomes visible, having the appearance
of a bright cone, if viewed in a darkened room. [more]
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