Thermistor - Honda Motorcycle Service Manual

ELECTRICAL FUNDAMENTALS
In the NPN type, almost no current flows when a positive
voltage is applied t o the collector and a negative voltage t o the
emitter. When a small current flows from the base t o the emit-
ter, a large current flows from the collector t o the emitter.
In this way, the transistor resembles an amplifier in that the
amount of collector t o emitter current is controlled by the base
current.
Transistors also resemble switching devices. The transistor is
turned on, allowing collector-to-emitter current t o flow, when
there is base current, and turned off when n o base current
exists.
Thermistor THERMISTOR SYMBOL
In general, the resistance value of most metals, including cop-
per, increases as the temperature rises.
When heat is applied to a substance, the activity of its
molecules increases and prohibits the flow of free electrons.
This increases the resistance.
In contrast, the resistance of a thermistor decreases as the
temperature rises.
This is because the number of free electrons increases as heat
is applied to the thermistor. In this case, the activity of the
molecules no longer obstructs the flow of electrons and the
resistance decreases.
Date o f Issue: March. 1995
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HONDA MOTOR CO.,LTD.