Induced Currents and Magnetic Fields

[twalters84]

Homework Statement

The north end of a bar magnet is pushed downward toward a wire loop in the plane of the paper. In which direction is the induced current, and which way is the induced magnetic field?

A. clockwise, into the paper
B. clockwise, out of the paper
C. counter-clockwise, into the paper
D. counter-clockwise, out of the paper
E. There is no induced current.

Homework Equations

I found a statement in the book that says the direction of an induced current is always opposes the change in magnetic flux that induces the current.

Edit: I just found a statement that says:

The direction of the magnetic field is perpendicular to the wire and is in the curling direction of your right hand fingers. The direction of your thumb is the direction of electric current.

The Attempt at a Solution

The answer key states the answer is D. However, the key is not always correct.

Direction problems always get me confused. If anybody could explain this problem to me perhaps I could get a better idea of what is going on here. Thanks in advance!

 

[dlgoff]

First you need to determine the direction of the induced current in the loop (What does your text say about inducing a current with a changing magnetic field?). Then use your right hand thumb rule.

 

[piercas]

I would like to clarify the concept of induced currents and magnetic fields in this scenario. When the north end of a bar magnet is pushed downward towards a wire loop in the plane of the paper, the magnetic flux through the loop is changing. This change in magnetic flux induces an electric current in the loop, following the direction of the induced magnetic field.

According to Faraday's law of induction, the direction of the induced current is always such that it opposes the change in magnetic flux that induces it. In this case, the magnetic flux is increasing, and therefore the induced current will flow in a direction that creates a magnetic field in the opposite direction, opposing the change in flux.

Using the right-hand rule, we can determine the direction of the induced magnetic field. If we curl our fingers in the direction of the magnetic field (from the north end of the bar magnet towards the wire loop), our thumb will point in the direction of the induced current. In this scenario, our thumb points out of the paper, indicating a counter-clockwise direction for the induced current.

Therefore, the correct answer is C. Counter-clockwise, into the paper. It is important to note that the direction of the induced current and magnetic field can change depending on the direction of the change in magnetic flux.