I'm making a circuit that lights up some LEDs
My power source is a 9V battery and I've calculated that I need 1ohm resistor on all series of LEDs (See Circuit "A" in the photo below)
Can I use a single resistor at the beginning of the circuit to light up all the LEDs ? If yes, what would be the value. (See Circuit "B" in the photo below)
Now, If I want to array like that about 100 LEDs.. will a 9V battery be enough to keep the light on for a couple of hours? What is the formula to calculate that?