The insides of 9V battery : r/diyelectronics

Simple LED circuit with 9V battery – helloCircuits!

Testing the 9V Battery Hack (or: Assault on Battery) – xkcd

File:9v battery and led circuit components (wires, battery, LED, resistor).jpg - Wikimedia Commons

The inside of a 9v battery. : r/mildlyinteresting

DIY Electronics - Circuit Basics

9V 1A AC DC 100V-240V Power Supply Adapter Cord for Arduino UNO R3 MEGA, US Plug - Center Positive 5.5x2.1~2.5mm : Electronics

Photoresistors - Physical Computing

This post describes how to make a Police LED flasher Circuit using a 555 Timer IC and BC 547 NPN Transist…

From Battery-powered to USB Christmas Lights : 6 Steps (with Pictures) - Instructables

Inside a 9-Volt Battery - RF Cafe