Student Exploration: Magnetic Induction
Vocabulary: current, induced magnetic field, magnetic field, Pythagorean Theorem, right-hand rule
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
Where does the needle on a compass normally point?
What will happen to the compass needle if you hold a magnet close to it?
A compass is a useful tool for measuring the direction of a magnetic induction field—more commonly called a magnetic field—because the needle's northern tip points in the direction of a field. In the Magnetic Induction Gizmo™, you will use compasses to measure the magnetic field caused by a current.
The SIMULATION pane shows an overhead and front view of a table with a wire threaded vertically through its center, perpendicular to the surface of the table. Check that the Current is set to 0 amps.
Drag a compass to several different locations on the SIMULATION pane. Where does the compass needle point?
The effect you see is due to Earth's magnetic field.
Slowly increase the Current value from 0 to 60 amps. Describe what happens:
Move the compass around on the table. What do you notice?
Get the Gizmo ready:
Set the Current to 0 amps.
Goal: Use compasses to determine the direction of magnetic field induced by a current in a wire.
Predict: Place the compasses in a circle around the wire as shown at right. What do you think will happen as you slowly drag the Current slider all the way to the right?
The compasses will start to form a circle around the wire
Test: Use the Gizmo to test your prediction. Describe the results:
Observe: Look at the Front view on the SIMULATION pane.
In which direction is the current moving through the wire?
(Note: The current direction shown is the direction of positive charge. In reality, electrons move in the opposite direction through the wire.)
Predict: Scientists use the right-hand rule to predict the direction of an induced magnetic field—or a magnetic field created by a current. To use the right-hand rule, position your right hand so that the thumb points in the direction of the current. The magnetic field lines wrap around the wire in the same direction as the fingers of your right hand.
If the current was pointed down, will the induced magnetic field be clockwise or counterclockwise?
Test: Set the Current to -60 amps.
In which direction is the current now moving through the wire
What is the direction of the induced magnetic field?
On your own: Use a battery, wire, and small compass to demonstrate magnetic induction. Describe your results in your science journal or notebook.
Magnetic field interactions
Get the Gizmo ready:
Remove all the compasses from the table.
Turn on Show grid and Show magnetic field sensor.
Set the Current to 0 Amps.
Question: How does Earth's magnetic field interact with an induced magnetic field?