What causes large electric resistances?
Thin wires or wires made of poor conductors. Some metals are simply better at carrying current without wasting energy than other metals. It has to do with how often a charge bounces off of a metal atom and loses energy. Copper, Silver, and Aluminum are good conductors while stainless steel and lead are pour conductors. Metals tend to become better conductors as you cool them and worse as you heat them. Semiconductors such as carbon (graphite) are poor conductors but have the reverse temperature effect. At low temperature they are poor conductors but become good conductors at high temperature.