Idea 4of 4Builds onThe lever, not the amplifierOnly change induces
Why only AC
Why won't a transformer work on a battery?
Today you'll discover
- what a battery's current does inside a transformer
- what a current that keeps reversing does
- why the grid chose AC
Think firstA transformer fed from a battery. Nothing comes out
A transformer's primary is connected to a battery. The secondary gives nothing. Why?
Decide first, then press Next. Compare the still magnet with the moving one.
A magnet, a coil and a meter. After a prediction, the magnet rests inside the coil with the needle at zero, then the frames alternate the magnet moving in and out with the needle swinging each way. The last step asks whether a charger's transformer could run from a battery.
See the whole ideathe big idea and the key word, in one place
The big idea
Transformers need a changing field, so the grid uses alternating current.
Easy to get wrongA transformer refuses DC not because the voltage is wrong but because nothing changes. Only change induces.
Key word
- alternating current
- current that reverses direction periodically, 60 times a second on the North American grid; its changing field is what transformers need
About this modelOnly CHANGE induces: a still magnet, however strong, induces nothing. Faster change, bigger swing.
Only CHANGE induces: a still magnet, however strong, induces nothing. Faster change, bigger swing.
Ready to use it?
- Explain why a transformer works on AC and not on a battery.