Step-up or step-down

Transformers come in two kinds, sorted by one question: which voltage is greater, the secondary's or the primary's?

One transformer takes in 120 V and gives out 600 V. Its secondary voltage is greater than its primary voltage.

A transformer whose secondary voltage is greater than its primary voltage is called a step-up transformer.

Another transformer takes in 120 V and gives out 24 V. Its secondary voltage is smaller than its primary voltage. It is called a step-down transformer.

You can also sort by turns. Earlier in this topic you saw that more turns on a coil means a bigger induced EMF. Winding more turns onto the secondary than the primary makes the secondary voltage greater.

This transformer has 200 primary turns and 1400 secondary turns. The secondary has more turns, so the secondary voltage is greater. It is a step-up transformer.

Now the same transformer's windings are swapped: 1400 primary turns and 200 secondary turns. The secondary has fewer turns, so the secondary voltage is smaller. It is a step-down transformer.

A transformer with 100 primary turns and 2000 secondary turns is a step-up transformer.

Quick-fire drill

Here are six fast sorts. Some give the turn counts, some give the voltages.

Your turn