More current, stronger field
The field grows as the current grows.
Turning up the current
A current flows in a wire that lies just above a compass. The needle turns away a little from north.
The current is now made larger. What happens to the turn of the needle?
What this lesson covers
The idea
The magnitude of the magnetic field produced at a given point by a current-carrying wire increases as the current through the wire increases.
Turning up the current
A current flows in a wire that lies just above a compass. The needle turns away a little from north.
The current is now made larger. What happens to the turn of the needle?
- It turns more
- It turns less
- It stays the same
Change the current
Move the slider. Watch the needle and the bar for the magnetic field.
Bigger current, bigger turn
The needle is deflected more when the current is larger. The needle only shows how strong the magnetic field of the wire is at its place. So a larger current gives a stronger magnetic field at that place.
The magnitude of the magnetic field produced at a given point by a current-carrying wire increases as the current through the wire increases.
Notes
The magnetic field at a given point near a current-carrying wire increases as the current increases.
Check yourself
The current in a wire is increased. The magnetic field produced at a given point near the wire…
A compass needle near a wire turns a little. Without moving the compass, how can the needle be made to turn more?
Which gives a stronger magnetic field at the same point near a straight wire?
- decreases. The field gets stronger, not weaker, as the current increases.
- increases — correct. Yes!
- stays the same. The needle turns more when the current is increased, which shows that the field changes. It increases.
- Decrease the current through the wire. A smaller current gives a weaker field and a smaller deflection.
- Move the compass farther from the wire. Farther from the wire the field of a given current is weaker, so the needle turns less.
- Increase the current through the wire — correct. Yes!
- A larger current in the wire — correct. Yes!
- A smaller current in the wire. The field increases as the current increases, so a smaller current gives a weaker field.
- No current in the wire. With no current the wire produces no magnetic effect on the compass, so the field of the wire is not stronger.