Circuit Simulator - Step-Up Transformer

Here we have a transformer with 10 times as many windings in the secondary (on the right) than in the primary (on the left). As a result, the voltage in the secondary is 10 times the primary voltage. (It's not exactly 100V 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 1/10th of the primary current.