current and charge

What are two conditions that must be met for an electric current to flow around a circuit?

1. The circuit must be complete

2. There must be a source of potential difference

What are charge carriers?

Charged particles responsible for carrying electric current

What are the charge carriers in metals?

Conduction electrons

How do conduction electrons behave inside a metal?

They move about freely, repeatedly colliding with each other and the fixed positive ions in the metal

What carries charge when an electric current passes through a salt solution?

Ions

What direction is convention flow?

Positive terminal to the negative terminal

The 3 ways to classify materials electrically

Conductors, insulators, semiconductors

Describe an insulator

Each electron is bound to an atom and cannot move away from the atom. When a voltage is applied across an insulator, no current passes through the insulator, because no electrons can move through it.

Describe a metallic conductor

Most electrons are attached to atoms but some are delocalised. The delocalised electrons are the charge carries in the metal. When a voltage is applied across the metal, these conduction electrons are attracted to the positive terminal of the metal

Describe a semiconductor

The number of charge carriers increases with an increase of temperature. The resistance of a semiconductor therefore decreases as its temperature is raised.

What is a pure semiconducting material referred to as and why?

An intrinsic semiconductor, because conduction is due to electrons that break free from the atoms of the semiconductor