Multisim - AND Gate Always Giving An Output

Question

I recently downloaded Multisim to give it a try. I used it many years ago and recently have a need to design some circuits so it was my first go-to. However, I am run into issues where the application does not seem to be simulating correctly.

I was attempting to build a boolean logic circuit to simulate the logic (A && ~B) || (A && B) but the output LED was always on. So to try and figure out what was wrong, I attempting to hook up a single AND gate to the LED with both inputs connected to switches, which in turn was connected to a 5V DC source. The issue is that when I start the simulation, the LED is always on, even if I start the simulation with both switches open.

This is the simple AND gate output I tried:

(NOTE: I did have a resistor for the LED as well previously, but it made no difference).

If I remove one of the connections to the AND gate, then the light will stay off (which is what I expect):

But as soon as I hook up a 5V supple to one of the inputs, the output is high:

It seems like that regardless of the switch position, the switch is always giving a high output; it never goes low. I feel like there is something very simple I am missing but I am not clear on what it is.

Can anyone explain why the switch is always giving a high output, causing the gate to be high, regardless of the positions? I even took this circuit directly from a YouTube video where the creator showed it working, but it doesn't work locally for me. TIA

Answer 1

So after much Googling and testing, it seems that when using switches with logical components (i.e., boolean gates, latches, etc.) you need to add a ground to each switch like so:

This is apparently because the switches opened position is models as two, high resistance, parallel resistors which still give a voltage to the logic inputs. So something like this won't work:

I personally don't like this solution as it tends to clutter the layout, but at least I can actually work on my designs in the meantime. I am hoping I am still missing something and someone can provide a cleaner solution for this.