Charges and electrons

This lesson connects atomic structure to behavior:

1. The law of charges (attraction / repulsion).
2. What “electricity” means at particle level.
3. Valence electrons and why the outer shell matters.
4. The idea of electron flow in a circuit (preview of Unit 2).

Memorize this field rule:

Like charges repel. Unlike charges attract.

• Two negative regions push apart.
• Two positive regions push apart.
• Positive and negative pull together.

Static cling, lightning, and motor torque all obey this rule. It is not optional physics — it is the behavior you troubleshoot.

Positive charge → lack of electrons (object lost electrons).

Negative charge → excess of electrons (object gained electrons).

Neutral → balanced protons and electrons.

In a battery or generator, the potential difference between regions is what can push electrons through a conductor — but only if there is a complete path (Unit 2).

In this course, electricity is defined as a flow of electrons.

That flow is current. Before current exists you need:

1. A source of potential difference (voltage).
2. A complete path (closed circuit).
3. A conductor.

Static electricity (Unit 3) is charge without sustained flow. This lesson sets up the difference.

Valence electrons live in the outer shell of an atom.

They are the electrons that:

• form bonds with other atoms,
• can be freed to carry current in conductors,
• are tightly held in insulators.

The textbook groups materials by valence count:

In metals like copper, outer electrons are not tightly bound to one atom. They become free electrons that can drift when a voltage is applied.

More valence electrons in the “conductor range” usually means more available charge carriers in the metallic bond model used at this level.

That is why silver, copper, and aluminum are excellent conductors — not because the wire is “full of electricity fluid,” but because electron movement is easy.

Insulators tend toward a full outer shell (stable octet). Electrons are tightly bound.

Rubber, glass, and most plastics used on cable insulation fit this pattern. They block electron flow — which is exactly what you want on everything except the intended conductor.

Never treat “insulator” as “no electricity ever.” High voltage, moisture, or damage can still break down insulation.

Unit 2 introduces two flow conventions:

• Electron flow theory: current flows from negative to positive (electrons are negative).
• Conventional current: older schematic convention, positive to negative.

This text uses electron flow as the primary explanation. You will still see conventional arrows on some symbols — know both, argue neither on a job unless the diagram requires it.

Situation. After pulling wire, a helper says: “I got shocked — electricity leaked out of the neutral because it was full.”

How to think with this lesson.

• Shock = charge equalizing through your body (often static or fault path).
• Neutrals carry return current in normal operation; they are not a “overflow tank.”
• Insulation failure or missing ground creates unintended paths — not because electrons “spill when full.”

Lead answer: “Current needs a complete loop. You became part of a path. That’s charge and potential difference — not a filled pipe.”

Learning conclusion: charge behavior + valence explain why materials and paths matter.