Hi, I'm trying to learn electronics, I'm right at the beginning,
just learned Ohms law and Watts law. I understand both. I understand
how to calculate both. However, I went to this tutorial on
Electronicsworkbench.com and I'm confused about how they come up with
these numbers.
In this example there is a series circuit with a 15v battery, a 10w/12v
light bulb with a voltmeter reading the voltage across the bulb and you
have to choose between 3 different resistors that will enable the bulb
to light - 1ohm, 100ohm and 5ohm. If you connect the 1ohm, the
voltmeter reads 15volts. How can that be ? In a series circuit each
load has some resistance and the sum of all the loads must equal the
source. So, what about the resistor ? It has to drop some voltage but
according to this, it's dropping zero. And if you connect the 100
ohm resistor, the voltmeter reads 1.88v. How did they come up with
that number?
---
See below.
---
And the 5ohm reads 12v across the voltmeter. But
according to Ohms law, E = IxR, if the resistor is 5ohms and the source
is 15v, then 15/5 = 3amps,
---
If the lamp weren't in the circuit you'd be right, but since it is
and you neglected to add its resistace into the string, that's where
you got 3 amps, which is wrong. See below.
---
that part I get but they are saying it's
dropping 3 volts ?? huh? Again, how did they get that value ?
http://www.electronicsworkbench.com/understandelectricity/ewb.html
---
Electronics workbench is a POS simulator, and this "tutorial" seems
to follow suit.
Looking at the first example you cite, the circuit looks like this:
+15V
|
+<-------+
| |
[LAMP] [METER]
| |
+<-------+
|
[1R]
|
GND
