Data Sheet

Project 25
Double Voltage Shifter
This project is similar to the preceding one, but uses three lamps. Build
the circuit, and set the meter (M5) to the 5V setting. The lamps (L4) are
on dimly and the meter measures the voltage across the top lamp. Push
the press switch (S2) to turn off the bottom lamp. Turn on the slide switch
(S1) to turn off the middle lamp. Disconnect the battery holder when you
are finished with this project.
The voltage you measure with only one lamp on should be double the
voltage with two lamps on, and triple the voltage with three lamps on.
The voltage divides evenly, because the lamps all have the same char-
acteristics.
This is another example of how voltage divides as parts are added in
series. The lamps are acting as resistors, because they limit the flow of
electricity in the circuit. As resistances are added in series, they add to-
gether to reduce the current.
With all three lamps on (both switches off), what is the voltage meas-
ured across the top lamp?
With all lamps on, what do you think the voltage across each other
lamp is? Swap the location of the meter with either switch to see if
you are right, then swap them back.
Turn on one or both switches, and compare the voltage measured
with one, two, or all three lamps on.
Why did the voltage change?
5V
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