I have a 4.5V source. I connected + terminal to a 15ohms resistance the resistance is connected to the + end of a green LED, the - end of green LED is connected back to the battery to make the circuit complete . I observe the green LED lights up. The drop across the resistance is 1.3V and the led is 3.2V.
Now I connected the Vcc of NTE74LS08 ("and gate") to the +-terminal of battery. The ground of NTE74LS08 is connected to the negative terminal of the battery.
pin 1 and 2 are 1A and 1B pin 3 is 1Y of NTE74LS08.
I connect 1Y with another + end of a red LED, the - end of the red LED is connected to 15 ohms resistance. The end of the resistance is connected to the negative terminal of the battery.
I observe even without the 1A and 1B connection (that is both the A and B input being zero) the red LED is lighting up.
My question is what is the mistake of my design ? Why is the any gate not working ?