i'm experimenting with transistors, and wired one to my circuitboard. Though I got the LED to turn on with a NPN transistor, I'm not sure it's setup properly.
I read that current moves against the direction the arrow is pointing for the transistor symbol (emitter to collector), so I wired the emitter to a higher voltage (7.5V) than the base (4.5V). The problem is, when I remove the voltage source to the base, the LED remains lit. Shouldn't it turn off if the base truly acts like a switch for current flowing from emitter to collector?
I included two schematics below, one a crude, most likely incorrect representation of my circuit, and another from a book I'm learning from. My attempt at making a circuit follows my failure to get the schematic in the book to work – please let me know if you spot any errors in either schematic.
simulate this circuit – Schematic created using CircuitLab
Best Answer
That is truly a very poor diagram in your book, throw it away. You have also made mistakes in transcribing it.
This is much better. It is drawn as a conventional circuit, with GND at the bottom, and increasing voltage generally up the page, with conventional current flowing downwards (hint, in the direction of the BJT emitter arrow), which makes it much easier to read and interpret.
simulate this circuit – Schematic created using CircuitLab