Light bulb and

battery

Inside a

A charged battery is kind of like a bucket full of electrons.

The electrons only want to race from the bottom (negative terminal) to the top (positive terminal).

They will do work on the way, but only if they have to.

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sNegative terminal

Positive terminal

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But there must be a complete circuit or no electrons can flow.- -

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sNegative terminal

Positive terminal

A gap in the circuit stops the flow of electrons.

This won’t light up the bulb because there isn’t a complete circuit.

Electric current must have a circuit.

It must get back to where it started.

Now there is a circuit, but it still won’t light up the bulb.

Electric current is flowing, but it’s not going through the bulb.

Current will always go the easiest way.

This current can get back to the battery without going through the filament.

It won’t go through the bulb unless it has to.

Flow of electric current

The bulb will only light up if the current flows through the filament.

filament

The bulb is designed with one wire connecting the filament with the base and the other side of the filament connected to the contact on the bottom.

Blue wire connects filament to base.

Green wire connects filament to contact.

The bottom of the bulb shows the contact and base being separated by a black ring of insulator material. Current can’t flow through the insulator so it must flow through the filament to get from the base to the contact.

base

insulator

contact

One wire must touch the base and the other wire must touch the contact

Base

Contact

Current can’t flow through the insulator so it must flow through the filament to get from the base to the contact.

Wire coming from bottom of the battery

Wire going back to the top of the battery.

Flow of electric current

Now the current must go through the filament to get back to the battery.

Now there is a circuit, and the bulb is on.

Electric current is flowing through the filament.