Step-Down Transformer

Circuit Description:

Here we have a transformer with 10 times as many windings in the primary (on the right) than in the secondary (on the left). As a result, the voltage in secondary is 1/10th the primary voltage. (It's not exactly 12V because of resistance in the primary and imperfect coupling between the two windings.)

If the secondary were shorted (the resistor replaced with a wire), the primary current would be much greater, and the secondary current would be 10 times the primary current.

Source: http://www.hqew.net/circuit-diagram/Step$2dDown-Transformer_13396.html