What is the difference between Ohm's law and resistance? How does temperature affect resistance?

Resistance is the opposition to flow of electric current. V = IR: for a given voltage, higher resistance means lower current. Physically, resistance depends on: length (longer wire = more resistance), cross-sectional area (thicker wire = less resistance), material (resistivity), and temperature. Metals have low resistance because free electrons can move easily. Rubber has high resistance because electrons are tightly bound. Temperature effect: for most metals, resistance INCREASES with temperature (positive temperature coefficient) because increased atomic vibration impedes electron flow. For semiconductors like silicon, resistance DECREASES with temperature.