Fact 1: Electrical current running through a wire causes that wire to heat up.

Fact 2: Because of electrical resistance, the passage of electric current through wire produces heat.

Given the two facts above, answer the question "What causes heat in a wire?" with the following options: 
- sunlight
 - energy
 - resistance
 - unidirectional
 - kinetic energy
 - photons
 - rays or beams
 - energy barrier


 

   resistance      