Electromagnets and Conductors: The Effects on a Pendulum

[XigmaTek]

Question:
Describe what will happen when a magnet suspended in the form of a pendulum is affected by an electrical conductor in close proximity.

My working:
Lenz's Law states that the emf induced in a conductor will oppose the emf of the change that produced it. Let's say I designed my experiment this way...

[PLAIN]http://img191.imageshack.us/img191/562/assessment.png
the dotted line represents the trajectory of the pendulum (should be a perfect parabola shape..)

The magnet moving over the sheet of metal will produce eddy currents in the metal, which will oppose the magnetic field caused by the magnet. Thus, this will cause the pendulum to slow down faster and its period and amplitude will decrease much quicker than if there was no conductor.

Am I correct? What else can be said about this situation? Is there a changing magnetic field present here?
Thank youuuuu!

 

[phyzguy]

What you said about the EM is basically correct, but a couple of comments:

(1) Pendulums move on a circular path, not a parabola.

(2) The period of a pendulum is pretty much independent of the amplitude. The amplitude will decrease, but the period will not change.

 

[XigmaTek]

thanks for that info. but your second point would apply only to small angles.
how would i go about measuring the amplitude?
also, does it matter which end of the magnet (N or S) is facing the sheet of metal as it moves over it?

 

[phyzguy]

thanks for that info. but your second point would apply only to small angles.
how would i go about measuring the amplitude?
also, does it matter which end of the magnet (N or S) is facing the sheet of metal as it moves over it?

-You are correct, the period is only independent of amplitude only for small angles.
-To measure the amplitude, you need to measure the maximum deflection. You could take a time exposure picture or a movie and measure it off the picture.
-It doesn't matter whether it is the N or S pole, the effect is the same.

 

[rwisz]

Your understanding of Lenz's Law and its application in this experiment is correct. The presence of an electrical conductor in close proximity to the pendulum will cause eddy currents to be induced in the conductor, which will create a magnetic field that opposes the motion of the magnet. This opposing force will cause the pendulum to slow down faster and its period and amplitude to decrease quicker than if there was no conductor present.

In addition, the changing magnetic field caused by the motion of the magnet over the conductor can also induce an electric current in the conductor. This can be seen as a form of electromagnetic induction, where a changing magnetic field induces an electric current in a conductor. This current will also create a magnetic field that opposes the motion of the magnet, further contributing to the slowing down of the pendulum.

It is important to note that the strength and direction of the induced current and magnetic field will depend on the relative motion between the magnet and the conductor. If the magnet is stationary and the conductor is moving, the induced current and magnetic field will be in the opposite direction compared to if the magnet is moving and the conductor is stationary. This is known as Faraday's Law of Induction.

Overall, the presence of an electrical conductor in close proximity to a pendulum with a suspended magnet will have a significant impact on the pendulum's motion and period. It is an interesting phenomenon to study and can have practical applications in fields such as energy generation and magnetic braking systems.