Datasheet-1

Use the preceding circuit, but replace the lamp (L4) with the motor
(M1, “+” on top), with or without the fan. Compare the motor speed
with 3 batteries (Part A), 2 batteries (Part B), or 1 battery (Part C).
Try it with the fan and without the fan.
Does the motor speed change like the voltage does (are they proportional)?
Project 22
Motor at Different Voltages
Use the preceding circuit, but
replace the motor (M1), with
the white LED (D6, “+” on
top). Compare the LED bright-
ness with 3 batteries (Part A),
2 batteries (Part B), or 1 bat-
tery (Part C). The LED may
not light with 1 or 2 batteries.
Does the LED brightness change like the voltage does (are they proportional)?
Project 23
LED at Different Voltages
LEDs have a turn-on voltage thresh-
old that must be exceeded before the
LED produces any light, then bright-
ness increases quickly. The LED’s
threshold depends on the LED color
and characteristics but is typically
1.5V for red LEDs, and about 3V for
white LEDs.
!
WARNING: Moving parts. Do not
touch the fan during operation.
!
WARNING:
Do not lean
over the motor.
Project 24
Voltage Shifter
With both lamps on, what is the voltage measured across
the top lamp?
With both lamps on, what do you think the voltage across
the bottom lamp is? Swap the locations of the meter and
press switch to see if you are right, then swap them back.
With the press switch pushed, what is the voltage meas-
ured across the top lamp?
Is it double the voltage measured across the top lamp
when both lamps were on?
Why did the voltage change?
Is the top lamp brighter now?
Build the circuit, and set the meter (M5) to the
5V setting. Turn on the slide switch (S1); the
lamps (L4) are on and the meter measures the
voltage across the top lamp. Push the press
switch (S2) to turn off the bottom lamp.
One of the most basic rules for ana-
lyzing circuits is Kirchhoff’s Voltage
Law: the total voltage driving a circuit
must equal the voltage drops within it.
This project proves it because the total
voltage across both lamps equals the
voltage from the batteries: (Vbatteries =
Vlamp1 + Vlamp2)
Since the battery voltage driving the
circuit is the same, bypassing the bot-
tom lamp shifts all the voltage to the
top lamp. This follows Kirchhoff’s Volt-
age Law.
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