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Experiment objective:
understanding
the charging route of NPN transistor and its switching
function.
Circuit description:
Besides
amplifying the current, transistor is also used as a
switch. When the base of the transistor is connected
to positive voltage, transistor will conduct current
and LED will illuminate, vice versa.
The Experiment:
Wire
the circuit as shown in diagram. Check the terminals
of the transistor (T) and the diode (D) to make sure
no wrong insertion ismade. Connect the base of the transistor
to the positive voltage by connecting the red wire (W)
to spring no. 14 or no. 8. D will illuminate now since
electric current is allowed to pass through the transistor.
If the wire is connected to spring no. 20, D will not
illuminate since the potential of spring no. 20 is low,
so that T will not conduct current.
Functions of electronic components
(summary):
*Resistor R1
provides the base current;
*Resistor
R2 for limiting electric current and serves as a load
for the collector terminal of the
transistor;
*LED
(D) as indicator;
*Transistor
T as switch;
*Battery
for power supply.
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