An electronic circuit is a closed path formed by the interconnection of electronic components through which an electric current can flow. The electronic circuits may be physically constructed using any number of methods. Breadboards, perfboards or stripboards are common for testing new designs. Mass-produced circuits are typically built using a printed circuit board (PCB) that is used to mechanically support and electrically connect electronic components. Electronic circuits can display highly complex behaviors, even though they are governed by the same laws of physics as simpler circuits.