In my electronics studies, this was year 2 material. Year one's theory was fully dedicated to linear components (resistor, capacitor, inductor) + resolving linear networks, basic electronics laws, magnetism, motors, transformers.
For this question to be simple, you have to know Ohms law, and for the rest accept what people say. If you don't accept that, and want to dig deeper: The LED (diode, a non linear device, in the case of a LED a device controlled by current - not voltage ) and transistor (a plainly complex device that we try to control via simplification - and that simplification works particularly well when using it as a switch) are a step up from simple.
Luckily, when you are working with 3.3 or 5V, and working with common LEDs and transistors, you can just do what someone else did.
Kudos for digging deeper and wanting to know the why!
tangent: why is turning a LED on and off analogue electronics, and not digital electronics? Digital electronics deals with logic 1 and 0. "Gate Values". But a transistor and LED aren't digital gates. They are physical, hence analogue, components. They deal with Volts, Amperes, charges, .... There are gate level "transistors" (e.g.: a "NOT gate" IC is similar to the schematic of michaelkellett, abstracted to a gate). There are also logic value LED packages (that accept 5 or 3.3 V).
The combination of the LED + transistor + base resistor + series resistor, can be considered as a digital LED
In my electronics studies, this was year 2 material. Year one's theory was fully dedicated to linear components (resistor, capacitor, inductor) + resolving linear networks, basic electronics laws, magnetism, motors, transformers.
For this question to be simple, you have to know Ohms law, and for the rest accept what people say. If you don't accept that, and want to dig deeper: The LED (diode, a non linear device, in the case of a LED a device controlled by current - not voltage ) and transistor (a plainly complex device that we try to control via simplification - and that simplification works particularly well when using it as a switch) are a step up from simple.
Luckily, when you are working with 3.3 or 5V, and working with common LEDs and transistors, you can just do what someone else did.
Kudos for digging deeper and wanting to know the why!
tangent: why is turning a LED on and off analogue electronics, and not digital electronics? Digital electronics deals with logic 1 and 0. "Gate Values". But a transistor and LED aren't digital gates. They are physical, hence analogue, components. They deal with Volts, Amperes, charges, .... There are gate level "transistors" (e.g.: a "NOT gate" IC is similar to the schematic of michaelkellett, abstracted to a gate). There are also logic value LED packages (that accept 5 or 3.3 V).
The combination of the LED + transistor + base resistor + series resistor, can be considered as a digital LED
