Why the fuck doesn't the first LED light up?

Well, think about it... diodes are semiconductors, they only conduct a current if there's a large enough voltage difference across the path.

What voltage do you start with? How much does the voltage drop across the resistor in the first case (where the resistor is before the junction) versus how much the voltage drops in the second case (where it's after the junction)?

yo nigga, where yo LED's second terminal at and wat's it potential relative to ground?

>>16699527
Its a probe not an LED my bad.

>>16699528
what's the 2.5V next to the probe mean, because it sure as hell doesn't indicate what voltage the node is at.
perhaps it's the threshold voltage between on/off?
anyway, the left case is probing ground, and the right case is probing VCC, and i'm probing your mother's asshole

>>16699531
>I'm probing your mother's asshole
Rude.
The 2.5V is the threshold, yes

>>16699519 (OP)
in the right circuit, youre connecting your probe/LED directly to 5 V. in the left circuit, youre connecting it directly to ground.
do you know the formula for a voltage divider? calculate the intermediate node voltage for both of your circuits, remembering that a switch is ideally zero ohms.

>>16699533
then what's the problem? the first probe doesn't light because it's measuring 0 volts relative to ground and is thus below threshold and not illuminated.

>>16699535
I thought that the electricity would 'flow' into the probe wire...

>>16699537
and besides the Probe lights up when the switch is open...

>>16699537
an ideal voltage probe (what you have in this simulation) has infinite impedance, thus draws no current nor disturbs the potential of the node its testing

>>16699539
yes, because both terminals of the resistor are at VCC, nothing is tying one resistor to ground (the probe doesn't count, it has infinite impedance, so no current flows).
the entire upper half of the circuit floats to VCC, then.

>>16699535
>laughs in horrors beyond your comprehensions

>>16699519 (OP)

>>16699554
Good answer (no cap)

>>16699519 (OP)
First example the tested node is at ground potential. The Second example it is at Vcc. Not sure what is hard here. The bottom half of the 10kΩ resistor is 0V in both cases.

>>16699547
Looks like the heater string on my tube amps, except I normally make an artificial ground with two 100Ω resistors to ground from each leg of the secondary.