Idea 5of 7Builds onEvery current wraps a field
Coil it up
One loop makes a weak field. Want a strong one?
Today you'll discover
- what coiling the wire does to the field
- three ways to make it stronger
- a magnet you can switch off
Think firstThe same current through twice the turns
The same current flows through a coil with twice as many turns. The field inside?
Decide first, then press Next. Watch the field grow as the turns are added.
A row of loops of wire with straight field lines through its inside. After a prediction, the coil is redrawn with twice the turns and a stronger field, then its north end is marked. The last step asks how a scrapyard crane drops a car it has lifted.
See the whole ideathe big idea and the key word, in one place
The big idea
An electromagnet: many turns add their fields; switch it off.
Why it happensA permanent magnet is the same thing inside: countless tiny currents in its atoms, all lined up, that cannot be switched off.
Key word
- electromagnet
- a magnet made by an electric current in a coil, often around an iron core; it switches off with the current
About this modelConventional current, right hand: fingers with the current, thumb along the field inside. Reverse I and N swaps ends.
Conventional current, right hand: fingers with the current, thumb along the field inside. Reverse I and N swaps ends.
Ready to use it?
- Name three ways to strengthen an electromagnet and say why each works.