In a simple series circuit, why does the bulb light when you close the switch?

Imagine a simple series circuit with one 1.5V battery and one bulb. When the 1.5V battery is replaced with a 3V battery ...

Imagine a circuit with a 1.5V battery and one bulb. Imagine a similar circuit with a 3V battery and two bulbs. Which has the brightest bulbs?

Why might a bulb flash and go out when a 1.5V battery and a 3V battery are both connected across it in a simple series circuit?

What is the effect of changing the wire in a circuit from a straight thick wire to a straight thin wire?

What is the effect of changing the wire in a circuit from a straight thick wire to a longer (coiled) thick wire?

In a circuit diagram, what does a circle with a cross inside it represent?

What do the long straight lines represent in a circuit diagram?

How is a battery represented in a circuit diagram?