Maybe you've seen, and even connected, the green "ground wire" in a DIY electrical project ... a simple explanation. Here, I'll tell you what electrical grounding is, what it does, and why it's so ...
Adding more batteries to a simple circuit will increase the electrical energy, which will make a bulb brighter. Electricity can flow through the components in a complete electrical circuit.
Understanding the difference between watts and amps will help you safely navigate electrical projects ... basic understanding ...