Plusivo DM401B - Page 39

Now, let us calculate the value of the resistor. We have a 9 V battery, the voltage on the LED is 1.887 V, so
the voltage on the resistor is:
9 𝑉 − 1. 887 𝑉 = 7. 113 𝑉
Now, let us use Ohm’s law:
𝑅 =
𝑉
𝐼
𝑅 =
7.113 𝑉
20 𝑚𝐴
= 355. 7 Ω
And the closest standard value is 330 Ω.
Now, let us build the circuit again using a 330 Ω resistor and measure the forward voltage again and the
current.
The measured voltage in this figure is 2.007 V DC
The measured current in this figure is 18.78 mA.
18.78 mA is so close to 20 mA.
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Mastering the Art of Measurement (DM401B Smart Digital Multimeter) r.01 www.plusivo.com