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5K20.10 - Eddy Current Pendulum

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​5K20.10 - Eddy Current Pendulum

Title5K20.10 - Eddy Current Pendulum

Demonstrate an effect of electromagnetic force.

Assembly Instructions

The large, very heavy red electromagnet needs to be pulled onto a cart of the right height (DO NOT TRY TO LIFT IT).  Pull out the beige 200V, 17A power supply.  Connect the power supply to the electromagnet using heavy duty banana cables.  This is important because the current flow is too large for regular banana cables.  Set it up so that the instructor does not block the view of the students when needing to throw the switch on the system.  The pendulum assembly is stored on a separate storage base.  It is too tall to fit through the door if it attached, so initially set it up for testing, but remove the pendulum assembly before the cart is moved into the classroom and re-attach it once the cart is in its position.  Screw in the appropriate paddle for the experiment (solid aluminum disk or slotted aluminum disk).  Make sure there is a danger sign on the setup as the current is pretty large. 

Setup Time15
Operation Time
Preview Time5
Operation Instructions

There is a special framework for the large electromagnet so that a non-magnetic metal (aluminum) disk can swing as a pendulum through its gap. The magnet is energized and the pendulum is drawn back and allowed to fall coming to a halt when it reaches the poles. If the slotted disk is used, it will swing through the poles, but become damped as it continues to swing.


Demo on DimeNo
PIRA 200Yes
Export Instructions (if different)

The field induces currents in the disc which then have a force on them due to the field.  This force opposes the motion and the disc is brought to a halt.  But, with the slotted disc the slots break up the current paths so that the currents cannot build up.  Thus the opposing force does not build up to the same level. 

Category5 Electricity and Magnetism
Subcategory5K - Electromagnetic Induction
Keywordseddy currents
Construction Information
large electromagnet
metal disks for pendulum - solid, slotted, ring, split ring
power supply - 0-200VDC, 0-17A
banana cables - high voltage, heavy duty
Export Setup - variable gap magnet, solid paddle, slotted paddles, rod with paddle hanger, monopod with rod and rod clamp