GCSE revision: transformer efficiency

We actually made the transformers today. The a.c. caused the primary coil to become an electromagnet with an alternating magnetic field, first going one way inside the iron and then the other way. This meant that the electromagnet was turning on and off at a frequency of 50Hz. We could hear it humming. This wastes energy and makes the transformer less efficient. The wires heated up because of their resistance. This makes the transformer less efficient. The core is made from SOFT IRON which means that its magnetic areas called domains can be switched around very easily. If they weren't it would waste energy because the magnetic field needs to change direction with a frequency of 50Hz. The iron core was made of laminated strips. An odd thing is that the changing magnetic field can induce currents in the iron as well as the secondary coil, which would waste energy heating the core and make the transformer less efficient. Laminated sections reduce the effect of these induced currents which are called eddy currents.