In article .com,
David D wrote:
I have this question and I am wondering if someone can tell me the
formula and how they derived the answer (steps) - it is probably
simple, but I am learning this as I go :

Electronic
1) A simple circuit consists of a current limiting resistor in series
with an LED across a supply voltage of 5VDC. The forward voltage drop
is 1.5VDC and the forward current is 10mA. The series resistor would
have a value of:
a. 1k#
b. 500#
c. 350#
d. 100#

The formula for calculating the series resistor value is:-




(Vs-Vf)
R = -------
I

Where R is the resistance in ohms
Vs the supply volts
Vf the forward voltage drop
I the forward current in amps.

--
*The first rule of holes: If you are in one, stop digging!

Dave Plowman London SW
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