What are 6 changes in atmospheric variables that usually precede rain and 6 that precede fair weather?

What variables could be changes to produce a larger electrical current?

• A magnet moving in and out of a coil of wire generates an electrical current. What variables could be changes to produce a larger electrical current? Also Milk left open out of a refridgerator turns sour much more quickly than unopened milk kept in a refridgerator. What variables can affect the rate at which milk turns sour> Also When hot concentrated solution of copper sulfate was poured into a watch glass, small crystals started to grow around the edge of the solution. What variables could influence the growth of these crystals? I don't understand variables, please help. Thankyou :D

• Answer:

  Make the coil have more turns of wire. put an iron core inside the coil stronger magnet faster motion bacteria in the air settling on the milk temperature humidity .