And if we measure the current in this circuit.
The measured current in this figure is 3.280 mA.
Now, let us calculate the value of the resistor. We have a 9 V battery, the voltage on the LED is 1.886 V, so
the voltage on the resistor is:
9 𝑉 − 1. 886 𝑉 = 7. 114 𝑉
Now, let us use Ohm’s law:
𝑅 =
𝑉
𝐼
𝑅 =
7.114 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 1.996 V DC
36
Mastering the Art of Measurement (DM501D Digital Multimeter) r.01 www.plusivo.com
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