About the NPN Circuit Pt 1
The NPN collector is connected to the yellow wire, the center (base) of the NPN is connected to a resistor, and that resistor is connected to the other resistor and that is connected to another wire, which is connected to the battery.
How Buzzer Circuit Works
When you touch the wires together the alarm sounds because the circuit has been closed.
What is the terminal strip of the breadboard?
The columns of the terminal strips are connected vertically but have a top and bottom half. The bottom half it's not connected to the top half because they are two different sections.
The terminal strips are large bundles of holes.
How does the LED work?
the short end of the led goes to the negative side of the battery. the long end of the led hooks to the positive end of the battery.
What is the bus part of the breadboard?
It's the top row, or bottom row. The bottom row is negative, and the top row is positive.
About the Pushbutton LED Circuit
the button is letting current flow through the circuit when it is pressed