|
Alternating Magnetic Fields Make Transformers Work |
| Q.
How do transformers work? Can they work with DC currents? |
| A.
The transformer is a simple magnetic coupling device that works because the current through it is alternating (AC). No, direct current (DC), the one that you get from a battery, would not work. Alternating currents create alternating magnetic fields, which in turn can create alternating currents in other circuits nearby. In the case of DC, the magnetic field is static and it cannot create electric currents, unless a change is introduced such as a physical movement of the magnetic field.
|
|
A transformer is made up of two coils of insulated electric wire—a primary and a secondary— tightly wound on a looping magnetic steel core, a good conductor of magnetic fields. The magnetic field is induced from one coil into the magnetic core, which then travels to the other coil and induces current by a reversal process. Energy in the form of electric current on the primary circuit is transformed into a magnetic field and then back to an electric current on the secondary coil.
|
 |
 |
|
|
By adjusting the number of turns on each coil, it is possible to control the relationship of the current (and therefore the voltage) between the two coils (called transformer ratio). A transformer that takes a voltage of 7,200 volts on the primary side and gives a voltage of 240 volts for the farmstead on the secondary side is said to have a ratio of 30 to 1 (7,2000V / 240V = 30). The voltage is 30 times smaller on the secondary, but the current in the secondary coil is 30 times greater than the current in the primary coil.
|
|
The combination of voltage and current determines the electric energy level. By lowering the voltage and raising the current on the secondary, the same amount of electric energy is present on both sides of the transformer, as required by the physical energy conservation law. (Actually, a small amount of energy is lost inside the transformer during the transformation, so the amount of energy coming out is slightly less than the amount going in.)
|