Idea 1of 4Builds onEvery current wraps a field
Only change induces
Currents make fields. Can a field make a current?
Today you'll discover
- what a moving magnet does to a coil
- what a strong magnet held still does
- the one word the whole law turns on
Think firstA magnet pushed into a coil, then held still inside
The needle swings as the magnet goes in. Now the magnet is held still inside. What does the needle do?
Predict first, then press Next. Watch the needle when the magnet stops.
A bar magnet at the left, a coil in the middle, a meter at the right. After a prediction, the frames advance: the magnet moves in and the needle swings; the magnet rests inside and the needle sits at zero; the magnet moves out and the needle swings the other way. The last step asks whether a spinning coil carries a current.
See the whole ideathe big idea and the key word, in one place
The big idea
A changing field through a coil induces a current. Only change.
Easy to get wrongA strong field is not an induced current. A magnet resting in a coil does nothing. Power stations keep a coil turning, and the grid alternates, for this one reason: only change induces.
Key word
- induction
- the production of a voltage, and a current in a closed loop, by a changing magnetic field
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?
- Say whether a described arrangement induces a current, and why.