NPN transistors are key components ... In circuit diagrams or symbols, the legs of an NPN transistor can be ... a current flows through the 2.2kΩ resistor into the base of the transistor.

Symbol and photo of a variable resistor. two-terminal device for adjusting current; ... Transistors (NPN) Image caption, Symbol and photo of NPN transistor. acts as a switch or amplifier in circuits; ...