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Voltage measurements:
Using the multimeter as a
voltmeter, measure the power supply voltage and then measure
the voltages at points A, B and C.
What do you notice about your
results?
The four resistors are
connected in series, making a chain known as a
potential divider, or voltage divider.
The total voltage is shared between the four resistors and,
allowing for tolerance, each resistor receives an equal
share.
Modify the circuit, replacing
one or more of the 10
 resistors
with 1 or
100
values. Are the results as you expect?
The diagram below shows a
light sensor circuit built in a similar
way:
The circuit uses an
LDR, or light dependent resistor.
The resistance of the LDR changes with illumination. In the
dark, the resistance is high, up to 1 M
or more. When light shines on the LDR, the light energy
increases the number of charge carriers available to
transfer current, and the resistance falls. In bright light,
the resistance can be as little as 100
.
What happens to the output
voltage of the light sensor circuit when you cover the LDR
with you hand?
Is the output voltage HIGH
or LOW in the dark? |
