Crowded lines, strong field
Closeness of lines shows strength.
Two places near a magnet
Look at a picture of field lines. At one place the lines are packed close together. At another they are spread far apart.
Where is the magnetic field stronger?
What this lesson covers
The idea
The relative strength of a magnetic field is shown by how close its field lines are: the field is stronger, and the force on another magnet's pole greater, where the lines are crowded.
Two places near a magnet
Look at a picture of field lines. At one place the lines are packed close together. At another they are spread far apart.
Where is the magnetic field stronger?
- Where the lines are close together
- Where the lines are far apart
- It is equally strong in both places
Compare A and B
Press Next step to compare the lines and the force at A and at B.
Close lines, bigger force
A field line picture does not show only direction. How close the lines are tells us how strong the field is. A north pole of another magnet is pushed harder where the lines are crowded.
The relative strength of a magnetic field is shown by how close its field lines are: the field is stronger, and the force on another magnet's pole greater, where the lines are crowded.
Notes
The field is stronger where the field lines are crowded, and the force on a pole of another magnet is greater there.
Check yourself
In a picture of field lines, how is the strength of the field shown?
The lines are crowded near place P and far apart near place Q. The force on the pole of another magnet is greater…
Where is the magnetic field weaker?
- By how close the lines are to each other — correct. Yes!
- By the colour of the lines. Colour is not used to show strength. The closeness of the lines is.
- By the arrowheads on the lines. Arrowheads show the direction of the field, not its strength.
- at Q. The force is greater where the lines are crowded, which is at P.
- at P — correct. Yes!
- equal at both places. A different closeness of lines means a different strength. The force is greater at P where the lines are crowded.
- Where the field lines are crowded. Crowded lines show a stronger field.
- Where the field lines are longest. Strength is shown by how close the lines are, not how long they are.
- Where the field lines are far apart — correct. Yes!