Idea 7of 7Builds onThe right hand reads itThe net arrow
A current in a field feels a push
A wire with current between two magnets. What happens?
Today you'll discover
- what a field does to a wire carrying current
- what reversing the current does to the push
- how a loop is made to turn
Think firstA wire carries current across a magnet's field
A wire carries current across a magnet's field. What does the wire do?
Decide first, then press Next. Watch the heavy arrow on the wire, and which way it points.
A north pole block at the left and a south pole block at the right with field lines between them, and a wire seen end-on in the middle. After a prediction, a cross marks the current going into the page, then a heavy arrow shows the wire pushed up; the current is reversed and the arrow points down; then a rectangular loop is shown with its two sides pushed opposite ways so it turns. The last step reverses both the current and the poles and asks which way the push points.
See the whole ideathe big idea and the key word, in one place
The big idea
The motor principle: a current in a field feels a push.
Easy to get wrongThe push is on the wire, not on the magnets. The magnets' field pushes the moving charge, and the wire is dragged along with it.
Key word
- motor principle
- a current-carrying conductor in a magnetic field experiences a force at right angles to both the field and the current; the basis of every electric motor
About this modelThe force arrow is drawn on the wire, not on the magnets; it is the magnets' field pushing the moving charge.
The force arrow is drawn on the wire, not on the magnets; it is the magnets' field pushing the moving charge.
Ready to use it?
- Give the direction of the push on a described current in a field, and say what reversing the current or the field changes.